- 1Nutritional requirements of schoolchildren
- 2Findings of the National Diet and Nutrition Surveys
- 3Physical activity in schoolchildren
- 4Nutrition, physical activity and health in childhood
- ○ 4.1 Overweight and obesity
- ○ 4.2 Cardiovascular risk factors
- ○ 4.3 Iron deficiency anaemia
- ○ 4.4 Oral health
- ○ 4.5 Bone development
- ○ 4.6 Food allergy and intolerance
- ○ 4.7 Mental health
- 5Factors affecting food choice
- 6Food provision in school
- 7Food in the curriculum
- 8Promoting healthy lifestyles in children
- • Acknowledgements
- • References
Healthy eating and being physically active are particularly important for children and adolescents. This is because their nutrition and lifestyle influence their wellbeing, growth and development. The nutritional requirements of children and adolescents are high in relation to their size because of the demands for growth, in addition to requirements for body maintenance and physical activity. Data from the National Diet and Nutrition Surveys (NDNS) show that the contribution of protein to food energy intake has increased between 1997 and 2008/2009 in both boys and girls aged 4-to-18-years. The contribution of fat to food energy intake has decreased in boys and girls aged 4-to-10-years, and in boys aged 11-to-18-years; saturated fatty acid intakes have decreased in boys and girls of both age groups. A decrease in the contribution of non-milk extrinsic sugars to food energy has been found in the younger age group, whereas it has hardly changed in the older age group. The most recent NDNS data (Year 1 of the NDNS Rolling Programme) on micronutrient intake showed that low intakes of almost all minerals and vitamin A in boys and girls in the older age group, and also of riboflavin and folate in girls in the older age group were evident. In the younger age group, low intake of zinc was evident in boys and girls. Data on micronutrient status is as yet only available from the 1997 NDNS. There was some evidence of poor status of riboflavin, thiamin, vitamin C, folate, vitamin D and iron. A comparison of data from the Low Income Diet and Nutrition Survey (2003–2005) and the 1997 NDNS showed that children from low-income families tended to have higher intakes of whole milk; fat spreads; meat and processed meats; and non-diet soft drinks compared with children from the general population. Intakes of wholemeal bread; buns, cakes and pastries; semi-skimmed and skimmed milk; vegetables; fruit and fruit juices; and diet soft drinks were lower in children from low-income families.
Physical activity has a major impact on health at all stages of life. In children and young people physical activity is particularly important to maintain energy balance and therefore a healthy bodyweight, for bone and muscoskeletal development, for reducing the risk of diabetes and hypertension, and for numerous psychological and social aspects. There is concern that many children spend too much time engaged or sedentary activity and not enough time being active. In the UK, it is recommended that children undertake at least 60 minutes of moderate to vigorous intensity physical activity every day, and vigorous activities, including those that strengthen muscle and bone, should be incorporated at least three times a week. Children and young people should also minimise the amount of time spent being sedentary (sitting) for extended periods.
Data from the 2008 Health Survey for England suggested that 32% of boys and 24% of girls aged 2-to-15-years met the previous target to be active for 60 minutes each day. However, as only out-of-school activity was assessed, this is likely to be an underestimation of actual activity. Physical activity levels in girls dropped with age, whereas in boys no clear patterns were observed. The average reported time spent doing sedentary activities (excluding sleeping or school time) was 3.4 hours on weekdays and 4.1 hours on weekend days. The Scottish National Health Survey 2009 found that 69–72% of boys and 56–60% of girls in Scotland met the previous 60 minute-per-day recommendation. The large differences between England and Scotland can in large part be explained by the use of a revised questionnaire in the latest Health Survey for England. The Welsh Health Survey 2009 reported that 47% of boys and 29% of girls were physically active for at least an hour a day, whereas research in Northern Ireland has indicated that only 15% of 8-to-12-year-olds take part in 60 minutes of activity, which ‘made them out of breath or hot and sweaty’ everyday. In England, children and young people, in particular girls, from some ethnic groups (Black African, Indian, Chinese, Pakistani, Bangladeshi) had lower activity levels compared with the general population.
Trends in overweight and obesity in children and adolescents have become increasingly worrying. Data from the Health Surveys for England showed that rates of overweight and obesity have increased over the past 15 years, the overall increase being mainly due to increasing obesity rates. In Scotland, overweight and obesity levels in girls aged 2-to-15-years and boys aged 2-to-6-years have not changed considerably between 1998 and 2009, whereas more boys aged 7-to-15-years were overweight or obese in 2009 compared with 1998. For Wales and Northern Ireland, no data showing long-term trends of overweight and obesity are available.
Overweight and obesity are associated with an increased risk of various conditions in adulthood, but consequences of overweight and obesity are already observed in children. Obese children have been shown to already have many of the changes associated with vascular disease in adults, including insulin resistance, high blood pressure and elevated levels of blood cholesterol. Considered previously to be a disease of adults, in the last decade, type 2 diabetes mellitus has become a far more common occurrence in children and adolescents. In addition, multiple studies have suggested that childhood overweight and obesity track into adulthood. Evidence shows that there seems to be no single dietary or lifestyle factor that leads to overweight and obesity, but a variety of different, often interlinked factors, exist.
Oral health has clearly improved since the 1970s. Data from the Children's Dental Health Surveys show that in 1973, 12-year-olds had an average of 5 decayed, missing and filled teeth (DMFT), and in 2003, this had fallen to less than one DMFT. Fifteen-year-olds had an average of around 8 DMFT in 1973 and 1.5 DMFT in 2003. The highest proportion of children with dental decay was found in Northern Ireland, followed by Wales, and the lowest proportion was found in England (no information for Scotland available). The decrease in dental decay since the 1970s is mainly due to fluoridation of water and toothpaste and generally improved oral hygiene, although nutrition plays a role as well.
A sufficient supply of calcium and vitamin D, as well as being physically active, is important for healthy bone development. However, data from the most recent NDNS show that 11% of girls aged 11-to-18-years and 6% of boys of this age group have calcium intakes below the Lower Reference Nutrient Intake, suggesting insufficient intakes. Data from the 1997 NDNS found that more than 1 in 10 (13%) 11-to-18-years-olds had low vitamin D status (no newer status data available as yet).
Estimates of the prevalence of food allergy in the UK vary, but have been suggested to be around 5–8% in children, the incidence of perceived food allergies and intolerances usually being considerably greater than the actual prevalence. It has been suggested that avoidance of certain allergens at an early age may decrease the risk of food allergy, although not all experts share this view, some suggesting that there are critical periods in early life when exposure triggers normal immune system tolerance.
It has been suggested that diet affects mental health, including cognitive function and depression, although there is limited evidence. The best-studied factor, in relation to cognitive function, is breakfast consumption. There is some evidence that eating breakfast may improve cognitive function, but inconsistencies and shortcomings of many studies do not allow firm conclusions to be drawn. There is conflicting evidence on the effect of fish oils on cognitive function.
One way to improve dietary habits of schoolchildren is via food provided in schools. Standards for school food are available in all UK countries. In England, food-based standards for school lunches were introduced in 2006, followed by food-based standards for food other than school lunches in 2007. Finally, nutrient-based standards were implemented in primary schools in 2008 and in secondary schools and special schools in 2009. A survey found that, compared with 2005, caterers in English primary schools now provide a healthier lunch that meets food-based and most nutrient-based standards, with substantial increases in fruit and vegetable consumption (60% on average), and a 32% decrease in sodium intake, although improvements still need to be made for some nutrients (e.g. iron and zinc). The Scottish government has also set out nutrient standards for school lunches, and food and drink standards for school lunches and for school food and drinks other than school lunches. The regulations came into effect in August 2008 for primary schools and in August 2009 for secondary schools. In Wales, minimum food-based standards apply to primary and secondary schools. More stringent food-based standards for school lunches and other food and drinks served at school, as well as nutrient-based standards for school lunches, are outlined in the Appetite for Life Action Plan, but are not compulsory. In Northern Ireland, new food-based standards for school lunches were introduced and made compulsory from September 2007, and in 2008 were extended to include all other foods and drinks served at school. Nutrient-based standards for school lunches are not in place in Northern Ireland.
Nutritional standards for packed lunches prepared at home have not been set, and research in England has shown that the composition of these lunches is less favourable than lunch provided at school. Ways of improving the quality of packed lunches have been investigated, with only limited success. Other schemes, such as fruit and vegetable schemes and breakfast clubs, have also been initiated with the aim to improve the dietary habits of schoolchildren. Furthermore, each UK country has the study of food and nutrition incorporated into the school curriculum. Examples of other projects aiming to improve children's health include Change4Life and SmallSteps4Life; the Healthy Schools initiative; Food and Fitness in Wales; Healthy Eating, Active Living in Scotland; Investing for Health in Northern Ireland; MEND; Let's Get Cooking; and Food Dudes.
1 Nutritional requirements of schoolchildren
It has long been recognised that good nutrition is of crucial importance for the wellbeing, growth and development of children. Even though the energy cost of growth is a minor component of total energy requirements, growth rate is a sensitive indicator of overall dietary adequacy (Butte 2000). The nutritional requirements (in addition to energy) of children and adolescents are high in relation to their size because of the demands for growth, in addition to requirements for maintenance and physical activity. In the longer term, food patterns in childhood, particularly adolescence, can set the scene for future dietary preferences and eating behaviour in adult life. There is also substantial evidence that poor diet and poor physical activity patterns in childhood can lead to problems that manifest later in life, particularly in relation to heart disease, obesity, type 2 diabetes, osteoporosis and some forms of cancer.
Growth and development
Children are expected to gain about 30 cm in height and 12 kg in weight between the ages of 5 and 10 years. During this period, the rate of height gain slows gradually, and at the same time, weight gain increases slowly. While the proportion of bodyweight as fat remains constant for boys with normal weight, this increases slowly for girls. Up to the age of 8 years, boys are typically heavier than girls but, after this age, girls become heavier because of their greater fat gain, which is linked with puberty. Lean body mass as a proportion of total body mass remains greater in boys (Buttriss 2002a). See Sections 3.0 and 4.1 for detailed information on trends in obesity, physical activity and relationships between diet and bodyweight.
During adolescence (10-to-18-years), puberty is associated with an increased requirement for energy and nutrients (see Tables 1,2) because of the hormonally driven rate of increase in height and weight. In boys, the linear growth spurt resulting in increased height is greater than in girls and is accompanied by an increase in muscle growth. Concurrently, the physiologically driven rapid bone mass increase is accompanied by deposition of calcium and phosphate (see Section 4.5).
|Vitamin B1 (thiamine)||mg||0.7||0.7||0.9||1.1|
|Vitamin B2 (riboflavin)||mg||0.8||1.0||1.2||1.3|
|DRVs for macronutrients, for the population in general, i.e. all ages|
|Fat||% food energy||35|
|of which saturated fatty acids||% food energy||11|
|Carbohydrate||% food energy||50|
|of which starch, intrinsic sugars and milk sugars||% food energy||39|
|of which NMES||% food energy||11|
|Vitamin B1 (thiamin)||mg||0.7||0.7||0.7||0.8|
|Vitamin B2 (riboflavin)||mg||0.8||1.0||1.1||1.1|
|DRVs for macronutrients, for the population in general, i.e. all ages|
|Fat||% food energy||35|
|of which saturated fatty acids||% food energy||11|
|Carbohydrate||% food energy||50|
|of which starch, intrinsic sugars and milk sugars||% food energy||39|
|of which NMES||% food energy||11|
The 2004 Health Survey for England, which focused on minority ethnic groups, highlighted differences in average height between ethnic groups and in comparison to the general population (see Fig. 1) (Becker et al. 2006). This pattern was similar to that reported in 1999 (Erens et al. 2001), although in the earlier survey, the mean heights of Bangladeshi boys and Indian and Chinese girls were less than the average for the general population, whereas in 2004, they were not significantly different. See Section 4.1 for obesity prevalence rates in different ethnic groups.
Dietary reference values (DRVs)
DRVs are estimates of the requirements of energy and nutrients for groups of people, taking into account various factors that influence requirements including growth and development. DRVs are useful as a general guide for a whole population group, but they are not intended for the assessment of the needs of individuals. Examples of their use include interpreting outcomes of dietary surveys to detect low intake levels of population groups, setting standards for food provision, and planning meals in schools or hospitals. DRVs for a given nutrient comprise: (1) the Estimated Average Requirement (EAR), which is an estimate of the average requirement for energy or a nutrient – approximately 50% of a group of people will require less, and 50% will require more; (2) the Reference Nutrient Intake (RNI), which is the amount of a nutrient that is enough to ensure that the needs of nearly all the group (97.5%) are being met; and (3) the Lower Reference Nutrient Intake (LRNI), which is the amount of a nutrient that is enough for only the small percentage of the group (2.5%) who have low requirements.
Typically, DRVs for protein, vitamins and minerals for groups of children are expressed as RNIs. For energy, EARs are used as an indication of requirements. Use of RNI values (equivalent to the mean plus 2 standard deviations) is not suitable for energy, as this would mean that predicted intakes would be greater than most people's needs and hence would result in weight gain over a period of time. Energy requirements are influenced by physical activity levels, in particular, and can vary significantly depending on the amount of physical activity undertaken habitually. Guidelines for energy intake assume a sedentary lifestyle, as this is the situation for the majority of people in Britain, though increased activity is advised. DRVs for macronutrients are expressed in terms of food (or total) energy intake and again are population mean values rather than recommendations for individuals.
Tables 1 and 2 show the UK DRVs for energy and selected nutrients for children from 4-to-18-years.
Limitations of available data in 1991, when the DRVs were set, meant that the EARs for energy for 4-to-10-year-olds had to be based on intake data from a number of studies conducted in healthy well-nourished children in the UK and elsewhere (FAO et al. 1985; Department of Health 1989). However, energy expenditure data was available for older children 11-to-18-years (FAO et al. 1985; Schofield 1985). Since then, there is a greater understanding of the energy expenditure of children and adolescents, and the distribution of time spent in activities of differing levels of energy expenditure, largely as a result of the application of the doubly labelled water method and other techniques such as heart rate monitoring (Torun et al. 1996). In 2004, following an expert consultation of the Food and Agriculture Organization of the United Nations (FAO), the World Health Organization (WHO) and the United Nations University (UNU), new values for the energy requirements of infants, children and adolescents were proposed based on more accurate techniques for measuring energy expenditure (FAO/WHO/UNU 2004). These indicated that previous values had been overestimated for children under 10 years of age, and had been underestimated for children over 11 years of age and for adolescents. Compared with the old values, the new FAO/WHO/UNU recommendations were on average 18% and 20% lower in 4-to-6-year-old boys and girls, respectively and on average 12% and 5% lower in boys and girls aged 7-to-10-years, respectively. In children and adolescents aged 12 years and older, the revised estimates were on average 12% higher than the values produced in 1985 in both boys and girls.
The reference values for energy intake in the UK are currently being updated by the Scientific Advisory Committee on Nutrition (SACN), using data from studies that use the doubly labelled water method, as this has proved to be the most useful approach. Data were considered if the measurements obtained were judged to be representative of the current UK population. The draft recommendations were open for consultation in late 2009, and the final recommendations are expected in due course. As with the findings of FAO/WHO/UNU, the suggested EARs for younger children in the draft SACN report are lower compared with the EARs from 1991, whereas in children older than 10 years, the new draft EARs are higher compared with the 1991 values (http://www.sacn.gov.uk).
Desirable intakes of carbohydrates and fats are expressed as a proportion of total dietary energy. These take into account eating habits in the UK and the practical implications of dietary changes in line with those considered desirable for health. They have been calculated with the needs of the adult population in mind. While these values provide a useful guide for older (school age) children, the recommendation for fat, in particular, should not be applied in full to the diets of pre-school children especially where appetite is poor.
There are no specific figures for the desirable amount of fibre [non-starch polysaccharide (NSP)] for children. The Department of Health recommends that children should have proportionally lower fibre intakes than adults; the current UK DRV for adults is 18 g of NSP per day as measured by the Englyst method (Department of Health 1991). This equates to approximately 24 g if the Association of Official Analytical Chemists (AOAC) method is used (Lunn & Buttriss 2007).
SACN is currently reviewing the DRVs for fibre. Meanwhile, the European Food Safety Authority (EFSA) has defined fibre as non-digestible carbohydrates (including NSP, resistant oligosaccharides, resistant starch) plus lignin (EFSA 2007, 2010). This definition is in accord with methods of analysis approved by the AOAC. EFSA's definition of fibre has been adopted by the European Commission as the basis of fibre declarations on pack in Europe (European Commission 2008). EFSA's recommended intake level for adults is 25 g per day. For children, EFSA suggests that ‘dietary fibre intake of 2 g per MJ should be adequate for normal laxation in children, based on the dietary fibre intake that is considered adequate for normal laxation in adults (25 g, equivalent to 2 to 3 g per MJ for daily energy intakes of 8 to 12 MJ) and taking into account that energy intake relative to body size in children is higher than in adults’ (EFSA 2010).
For most essential nutrients, current UK requirements for children have been estimated by extrapolating published data for infants and adults, as little specific information for school-aged children existed when the DRVs were developed (Department of Health 1991). During adolescence, DRVs are set higher for boys than for girls because of their increased rates of growth, bone synthesis and bone mineralisation. The DRV for iron intake in post-pubertal girls is higher than for boys and is based on data from a study carried out in 1966, showing that once menarche is reached and periods start, girls lose on average the equivalent of 12.5 µmol of iron per day, although there is a wide individual variation in the amount of blood lost, with girls on the 95th centile losing around 34 µmol per day. Newer data from a recent study carried out in UK women found that on average, over a menstrual cycle, the mean iron loss was 7.7 µmol per day, and 70% of the women lost less than 9 µmol per day (Harvey et al. 2005). Discrepancies between iron intake data and iron status data (see Section 2) have led to discussions around whether the iron recommendations may be set higher than necessary, and some experts have suggested reassessing the DRVs for iron, although more good quality dose-response data are required (SACN 2010).
Sodium intake in children, as well as in adults, has been associated with increased risk of high blood pressure. Therefore, SACN has established target average salt intakes for adults and children (Table 3), which are upper intake levels (SACN 2003).
|Age (years)||Salt (g/d)||Sodium equivalents (g/d)|
Vitamin D supplements (in the form of vitamin drops also containing vitamins A and C) are recommended for children under the age of 5 years. For schoolchildren, there are no recommendations for dietary vitamin D intakes because it is expected that most people, with the exception of very young children, pregnant women and elderly people, obtain an adequate amount of the vitamin via the action of sunlight on the skin. However, it has become apparent that a substantial proportion of children have low vitamin D status (see Sections 2 and 4.5).
Various factors affect an individual's ability to produce vitamin D, including latitude, pigmentation of skin and style of dress. In higher latitudes, such as the UK, the wavelength of sunlight radiation is not sufficient during winter months. Research shows that even within the UK, there is a divide between the north and the south of the country, with observed vitamin D levels being lower in the north than in the south (Macdonald et al. 2010). Members of ethnic groups living in the UK, in particular those who have limited sun exposure because of the style of their dress, may not get enough vitamin D. There is currently insufficient data from some population groups, including South Asian and African-Caribbean groups, to estimate precisely the prevalence of low vitamin D status (SACN 2007). The Department of Health recommends that Asian children continue taking vitamin D supplements (10 µg/day) after the age of 5 years, particularly where religion and customs dictate that their skin is kept covered outside, resulting in limited exposure of their darker skin to the relatively weak sunlight available in the UK (Department of Health 1991). A SACN group has been set up to look at the evidence around vitamin D and health and to review the current DRVs (http://www.sacn.gov.uk).
Fluid requirements are an often overlooked aspect of diet. If lost fluid is not replaced, dehydration will result. In the short term, poor hydration causes headaches and constipation, and can cause irritability and impair mental performance, which is particularly relevant for schoolchildren. In the longer term, chronic mild dehydration is associated with increased risk of a number of conditions, including urinary tract infections, hypertension, coronary heart disease and stroke (Benelam & Wyness 2010).
It is generally accepted that six to eight glasses of fluid per day (appropriate for the size and age of the child, older children consuming larger drinks than smaller children) should be sufficient to replace water losses. However, children are less heat tolerant than adults and can become dehydrated more quickly when exercising, particularly in hot weather. Therefore, more water will be needed in hot weather and after vigorous physical activity (Benelam & Wyness 2010). In adults, thirst is a good indicator of fluid needs, if responded to promptly. However, children may need to be encouraged to drink sufficiently to rehydrate, e.g. after exercise, and provision of flavoured water is often more acceptable than plain water (Saltmarsh 2001). There is some evidence that patterns of drinking are established in childhood; therefore, it is important that children become used to maintaining an adequate fluid intake.
The importance of adequate hydration has been recognised and access to water has been included as a requirement in the various school food standards in the UK (see Section 6). In England, the food-based standards for lunch and other eating occasions at school include the requirement of having free-of-charge water available to children at all times. For lunch time, serving suggestions are made, including jugs of freshly poured tap water together with cups/glasses on tables and at the serving counter, installation of a point-of-use water cooler that uses mains water, and modern water fountains as an additional water point in the dining room (School Food Trust 2007). In Scotland, the Schools (Health Promotion and Nutrition) (Scotland) Act 2007 states that free drinking water must be available in schools at all times (The Scottish Government 2008a); and in Wales, the Appetite for Life Action Plan declares that schools need to ensure that schoolchildren have easy access to drinking water, at no cost, in an appropriate place and throughout the day (Welsh Assembly Government 2008b). The nutritional standards for school lunches in Northern Ireland (School Food: top marks) state that free water, i.e. tap water, must be provided every day (Health Promotion Agency for Northern Ireland 2008).
2 Findings of the National Diet and Nutrition Surveys (NDNS)
The NDNS provide comprehensive data on eating patterns of people aged 1.5 years and older living in private households in the UK. Comprehensive data are available from an NDNS carried out in 1997 in children aged 4-to-18-years (Gregory et al. 2000), in which the eating patterns and nutrient intakes of over 1700 schoolchildren and adolescents in Britain were assessed. More recent data is also available for the first year (2008/2009) of the NDNS Rolling Programme, currently commissioned for a total period of four years (i.e. 2008–2012) (Bates et al. 2010).* Preliminary data on 462 children are available and, until more data become available, have to be interpreted with caution. Also, because of the small sample size, data from schoolchildren are presented for only two age categories (4-to-10-years and 11-to-18-years) instead of the four categories in the earlier survey (4-to-6-years, 7-to-10 years, 11-to-14-years and 15-to-18-years). This means that comparison with DRVs, which are specific to the four subcategories used in the 1997 survey, was not always possible. The data will become more robust over the next few years. Nevertheless, the initial findings of the NDNS Rolling Programme give a useful insight into energy and nutrient intakes in young people in 2008/2009.
To be able to compare the data from 1997, which was based on a 7-day dietary record, with data from 2008/2009, which was based on a 4-day dietary record, the data from 1997 were re-analysed by the researchers carrying out the NDNS Rolling Programme (for more detail see Bates et al. 2010).
The mean energy intakes reported in 2008/2009 were comparable with the energy intakes reported in 1997 (see Table 4).
|Age (years)||1997 NDNS young people||2008/09 NDNS rolling programme year 1|
|MJ (kcal) per day||MJ (kcal) per day|
|4–10||7.08 (1680)||6.71 (1591)|
|11–18||8.95 (2130)||9.07 (2154)|
|4–10||6.34 (1510)||6.41 (1523)|
|11–18||6.98 (1660)||7.02 (1668)|
Comparison of the new data with EARs for energy (Department of Health 1991) was not possible, but data from the 1997 NDNS showed that for boys and girls in each of the four separate age groups studied, mean energy intakes were lower than the EARs for their defined age and gender groups (see Table 5). Energy intakes in 1997 were lowest in relation to the EARs for 15-to-18-year-old girls. This may be due in part to under-reporting of foods consumed, particularly in older girls. Even though the mean reported daily energy intakes were on average below the EARs, actual intakes are still likely to have been at least adequate in the context of existing physical activity patterns (given the statistics on overweight and obesity, see Section 4.1). Already in 1997, children were heavier and taller compared with earlier data from 1989, and it is therefore unlikely that children were not meeting their requirements for energy (Buttriss 2002a).
|Age (years)||MJ (kcal) per day||% of EARs|
Intakes of macronutrients in the 1997 NDNS Young People Survey and in Year 1 of the NDNS Rolling Programme are compared in Table 6. Table 7 reports the main contributors to energy and macronutrient intake in Year 1 of the NDNS Rolling Programme (Bates et al. 2010)
|1997 NDNS young people||2008/2009 NDNS rolling programme year 1|
|Protein, g/day (%E)||53.0 (12.6)||70.5 (13.5)||48.4 (12.9)||54.6 (13.4)||57.7 (14.5)||77.1 (14.8)||54.3 (14.4)||58.9 (14.5)|
|Total fat, g/day (%E)||66.6 (35.4)||83.6 (35.6)||60.3 (35.9)||66.0 (36.0)||60.2 (34.0)||81.6 (34.5)||59.5 (35.0)||65.9 (35.7)|
|Saturated fatty acids, g/day (%E)||27.3 (14.5)||32.7 (13.9)||24.9 (14.8)||25.6 (13.9)||23.8 (13.4)||30.4 (12.7)||23.4 (13.8)||24.1 (13.1)|
|Total carbohydrate, g/day (%E)||233 (52.0)||286 (51.0)||206 (51.2)||222 (50.8)||218 (51.5)||286 (50.7)||205 (50.6)||219 (49.8)|
|Total sugars, g/day (%E)||109.8 (24.5)||125.8 (22.1)||98.6 (24.4)||97.1 (21.9)||96.6 (22.7)||129.2 (22.6)||96.5 (23.5)||94.2 (21.4)|
|NMES, g/day (%E)||77.4 (17.2)||93.7 (16.4)||69.2 (17.0)||70.3 (15.8)||61.7 (14.4)||93.2 (16.3)||60.9 (14.7)||66.5 (15.0)|
|Nutrient||Food group||Contribution to intake (% of total)|
|4–10 years||11–18 years|
|Energy||Cereals and cereal products||35||33|
|Meat and meat products||14||17|
|Milk and milk products||15||9|
|Vegetables and potatoes||10||11|
|Non-alcoholic beverages (excluding milk)||5||7|
|Sugar, preserves and confectionery||6||6|
|Protein||Meat and meat products||30||38|
|Cereals and cereal products||27||26|
|Milk and milk products||21||14|
|Fish and fish dishes||5||4|
|Carbohydrate, total||Cereals and cereal products||46||43|
|of which bread||17||17|
|of which breakfast cereals||8||7|
|Vegetables and potatoes||11||12|
|Non-alcoholic beverages (excluding milk)||9||14|
|Sugars, preserves and confectionery||7||7|
|Milk and milk products||9||6|
|of which soft drinks||18||31|
|of which fruit juice||12||9|
|Cereals and cereal products||28||22|
|Sugar, preserves and confectionery||23||21|
|Milk and milk products||12||7|
|NSP||Cereals and cereal products||43||41|
|of which pasta, rice and other cereals||9||11|
|of which white bread||8||10|
|of which wholemeal, brown, granary and wheatgerm bread||10||7|
|of which wholegrain and high fibre breakfast cereals||7||5|
|Vegetables and potatoes||27||29|
|of which vegetables (excluding potatoes)||16||14|
|of which potatoes||12||15|
|Fat, total||Meat and meat products||19||25|
|Cereals and cereal products||23||22|
|Milk and milk products||20||13|
|Chips, fried potatoes and potato products||6||8|
|Sugar, preserves and confectionery||5||6|
|Saturated fatty acids||Milk and milk products||31||22|
|Cereals and cereal products||23||23|
|Meat and meat products||18||24|
|Sugar, preserves and confectionery||6||7|
Data from Year 1 of the NDNS Rolling Programme show that protein intake was higher compared with 1997 (Table 6). Even though direct comparison with RNIs is not possible because of the age categorisation in the Year 1 report, findings from the earlier report show that protein intakes were well above the RNI in girls and boys of all age groups (see Section 1 for protein RNIs). The main sources of protein in the diets of UK children are shown in Table 7.
The contribution of total carbohydrates to food energy in young people in 2008/2009 was similar to that in 1997 (Table 6), and was in both age groups close to the DRV of 50% of food energy (see Section 1). The main sources of carbohydrates in the diet of UK children are presented in Table 7.
In the NDNS report, sugar intake is reported as non-milk extrinsic sugars (NMES), and intrinsic sugars and milk sugars. NMES are sugars that are not contained within the cellular structure of food, whether natural, unprocessed or refined. NMES are typically present in table sugar, honey, fruit juice and all foods to which sugar has been added (e.g. cakes, biscuits, drinks, confectionery). In 2008/2009, NMES contributed on average 14.5% of food energy in 4-to-10-year-olds and 15.7% in 11-to-18-year-olds (Table 6). In 1997, the respective values were 17.1% and 16.0%, which means that there has been a decrease in the contribution of NMES to energy intake in 4-to-10-year-olds. The main sources of NMES in the diets of schoolchildren are presented in Table 7.
The average intake of fibre in the form of NSP was higher in boys than in girls in both age groups in 2008/2009 (Table 6). A specific DRV for NSP does not exist for children (Department of Health 1991). A slight increase in NSP intake between 1997 and 2008/2009 was observed in both age groups. The main contributors to NSP in the diets of young people are shown in Table 7.
The average contribution of fat to energy intake in young children and adolescents decreased slightly between 1997 and 2008/09 (Table 6). Findings from earlier reports showed that there had also been a decrease in average fat contribution to energy intake between 1983 and 1997 (see Buttriss 2002a). The older data showed that fat had been replaced by sugar, whereas the change from 1997 to 2008/2009 is suggestive of a higher proportion of food energy now coming from protein.
The most recent data show that average intakes were close to the recommended population average intake of 35% food energy. The main contributors to total fat intake are shown in Table 7.
Saturated fatty acid intake decreased between 1997 and 2008/2009 in both age groups (see Table 6). The average percentage of food energy from saturated fatty acids fell with age for both sexes, and was slightly higher in girls than in boys, but intakes remained above the recommended upper level of 11% of food energy in both age groups and both sexes in 2008/2009. The main contributors to saturated fatty acid intake are shown in Table 7. Together, foods that are typically found within the high fat and/or sugar food group of the Eatwell plate (e.g. confectionery (mainly chocolate confectionery), ice cream, savoury snacks, biscuits, cakes and pastries; see page 338) provide almost a quarter of fat and saturated fatty acids consumed by school-age children.
The average intake of cis n-3 and n-6 polyunsaturated fatty acids (PUFA) combined has decreased in both boys and girls (Table 6). Average intakes are below the combined DRV for cis n-3 and n-6 PUFA intake of 6.5% of food energy. The decrease in intake in both boys and girls was mainly due to decreases in n-6 PUFA intake, whereas n-3 PUFA intake as a proportion of energy intake has stayed at the same level or has slightly increased. The decreases in PUFA intake have also been observed in each age group. The new NDNS report does not provide data on the main dietary contributors to PUFA intake (this will follow in subsequent reports). In the 1997 NDNS (Gregory et al. 2000), the major contributors to n-3 PUFA intake were: the category vegetables, potatoes and savoury snacks (mainly roast and fried potatoes, and chips) providing 34% in boys and 38% in girls; cereals and cereal products (18% and 16%); and meat and meat products (17% and 16%). Fish and fish dishes, mainly coated and fried white fish, contributed 5% of cis n-3 fatty acids in boys and 6% in girls. The main contributors to n-6-PUFA intake in 1997 were: the category vegetables, potatoes and savoury snacks (providing 27% in boys and 29% in girls, respectively); cereals and cereal products (23% and 21%); meat and meat products (18% and 16%); and fat spreads (16% in boys and girls) (Gregory et al. 2000).
Tables 8 and 9 show the average daily intakes of vitamins and minerals in 2008/2009 compared with 1997 for boys and girls of different ages, expressed as average intakes, as well as the proportion of children having intakes below the LRNI. The LRNI is the amount of a nutrient that is estimated to be sufficient for only the few people in a group who have low needs (less than 2.5% of a population group), and therefore those who are below this level are likely to have insufficient intakes (Department of Health 1991).
|1997 NDNS Young People||2008/09 NDNS Rolling Programme Year 1|
|Average daily intake||% below LRNI||Average daily intake||% below LRNI||Average daily intake||% below LRNI||Average daily intake||% below LRNI|
|Vitamin A (retinol equivalent) (µg)||485||12||594||14||651||2||776||11|
|Niacin equivalents (mg)||24.7||0||33.5||0||27.9||0||39.4||0|
|Vitamin B6 (mg)||1.8||0||2.5||0||1.8||0||2.6||0|
|Vitamin B12 (µg)||4.0||0||4.8||1||4.1||0||4.8||0|
|Vitamin C (mg)||72.0||0||82.0||0||83.9||0||94.4||2|
|Vitamin D (µg)||2.3||-||2.9||-||1.9||-||2.5||-|
|Vitamin A (retinol equivalent) (µg)||470||12||524||19||660||3||619||10|
|Niacin equivalents (mg)||22.2||0||25.4||0||26.1||0||30.7||0|
|Vitamin B6 (mg)||1.6||0||1.9||0||1.7||0||2.1||0|
|Vitamin B12 (µg)||3.5||0||3.4||3||3.7||0||3.9||0|
|Vitamin C (mg)||71.6||0||73.8||0||81.2||0||72.4||1|
|Vitamin D (µg)||2.0||-||2.2||-||2.0||-||2.1||-|
|1997 NDNS Young People||2008/09 NDNS Rolling Programme Year 1|
|Average daily intake||% below LRNI||Average daily intake||% below LRNI||Average daily intake||% below LRNI||Average daily intake||% below LRNI|
By definition, if no more than 2.5% of a population have intakes below the LRNI, then the likelihood of deficiency in the group is low; however, Tables 8 and 9 and Figure 2 demonstrate that significant proportions of young people have low intakes of a number of nutrients and that the situation is worse in the older age group. Using a cut-off of 5%, low intakes of almost all minerals and vitamin A in boys and girls in the older age group, and also of riboflavin and folate in girls in the older age group were evident. In the younger age group, low intake of zinc was evident in boys and girls (Bates et al. 2010).
There is as yet no information available from the new NDNS Rolling Programme on the sources of vitamins and minerals in the diet. However, such information was available in the previous report and is presented in Table 10 for those nutrients identified as being of potential concern in the 1997 and 2008/2009 datasets.
|Nutrients for which low intakes* were evident||Main sources in the 1997 National Diet and Nutrition Survey of young people aged 4-to-18- years, with contribution (%) provided in brackets|
|Vitamin A (retinol equivalent)||Vegetables (excluding potatoes) (∼27%); milk and milk products (∼20%); meat and meat products (∼15%, half of which came from liver); fat spreads (∼13%); cereal and cereal products (∼13%)|
|Riboflavin||Milk and milk products (∼35%); cereal and cereal products (∼32%); meat and meat products (∼11%)|
|Folate||Cereal and cereal products (∼40%); vegetables, potatoes and savoury snacks (∼26%); milk and milk products (∼12%)|
|Zinc||Meat and meat products (∼31%); cereal and cereal products (∼25%); milk and milk products (∼20%); vegetables, potatoes and savoury snacks (∼12%)|
|Iron||Cereal and cereal products, particularly breakfast cereals and bread (∼50%); vegetables, potatoes and savoury snacks (∼17%); meat and meat products (∼14%)|
|Magnesium||Cereal and cereal products (∼31%); vegetables, potatoes and savoury snacks (∼22%) over half of which came from potatoes; milk and milk products (∼16%); meat and meat products (∼11%)|
|Calcium||Milk and milk products (∼48%); cereal and cereal products, particularly bread (∼27%)|
|Potassium||Vegetables, potatoes and savoury snacks (∼34%), with two thirds coming from potatoes; milk and milk products (∼17%); cereals and cereal products (∼15%); meat and meat products (∼13%)|
|Iodine||Milk and milk products (∼50%); cereal and cereal products (∼16%); fish and fish dishes (∼8%)|
The latest NDNS report does not provide nutritional status data. Therefore, this section will look at data from the 1997 dataset (Gregory et al. 2000). In general, nutritional status (as reflected by biochemical markers) was good, but there was evidence of poor status in some individuals for riboflavin, thiamin, vitamin C, folate, vitamin D and iron. For example, impaired riboflavin status was evident among children with low riboflavin intakes and evidence of low folate status was present in 9% of girls and 7% of boys. There was evidence of poor iron status in children aged 4 years, with 3% of boys and 8% of girls having low haemoglobin levels. Among girls aged 15-to-18-years, 9% had low haemoglobin levels. There was also evidence of low iron stores (as indicated by serum ferritin levels) in 13% of all boys and 14% of all girls, with the proportion rising to 27% in 15-to-18-year-old girls (see Section 4.3 for information on iron deficiency anaemia).
There was evidence of poor vitamin D status in the survey. Plasma levels of 25-hydroxyvitamin D (active form) fell with age, and significant proportions of those in the older age groups had a poor vitamin D status (as indicated by levels of less than 25 nmol/L). Overall, more than 1 in 10 (13%) 11-to-18-year-olds had low vitamin D status. There was strong seasonal variation in 25-hydroxyvitamin D status, with plasma levels being highest in blood samples taken between July and September and lowest for samples taken between April and June, when more than one in five 15-to-18-year-old boys had levels of 25-hydroxyvitamin D below the reference range. This reflects higher sunlight exposure during summer months (see Sections 1 and 4.5).
The micronutrient status data were less alarming than the intake data, which may suggest that the requirement estimates for some nutrients need reconsideration or that the biomarkers used to assess status are imprecise.
Information on dietary supplement use is available from the 1997 NDNS (Gregory et al. 2000). In 1997, one in five children in the NDNS survey were taking vitamin and mineral supplements. These young people tended to have higher intakes of vitamins and minerals from food sources than those who did not take supplements. Although supplement use made a significant contribution to intakes of iron, zinc and vitamin A, it did not influence the proportions of subjects with intakes below the LRNI.
Vegetarians and vegans
In the most recent NDNS, 2% of 4-to-10-year-olds and 3% of 11-to-18-year-olds were reported to be following a vegetarian diet (none were reported to be vegan). As the sample size in this report of the NDNS Rolling Programme was still relatively small, no sex-specific data are available. In the 1997 survey, 5% of girls and 1% of boys were reported to be vegetarian or vegan, with the proportion rising from 2% among 4-to-6-year-olds to 10% among the oldest girls (see Table 11 for details). No variation with age was found in boys. Vegetarians tended to come from non-manual family backgrounds. About two-thirds said they avoided meat for moral or ethical reasons and about a third said they did not like the taste of meat. Interestingly, parental or religious reasons were given far less often. Plasma iron and haemoglobin levels were significantly lower in vegetarians compared with omnivores. However, there was no difference in vitamin B12 status, despite the fact that it is only available naturally via foods of animal origin (principally milk and meat), though it is added to a number of fortified foods (e.g. breakfast cereals and soya products). Low-density lipoprotein cholesterol (LDL-C) levels were lower and the biochemical status of several vitamins and of selenium was higher among the group consuming a vegetarian diet (Gregory et al. 2000).
|Age (years)||% reporting being vegetarian or vegan|
|Social class of head of household:|
Regional and socio-economic differences
Data on regional and socio-economic differences in food and nutrient intake are available from the 1997 NDNS (Gregory et al. 2000). The NDNS study population was divided into four regions: Northern England; Central/ South West England & Wales; London/South East England; and Scotland. Information from the Low Income Diet and Nutrition Survey (LIDNS) (Nelson et al. 2007), which examined dietary and lifestyle habits of UK citizens on low income, is also included in this section.
Types of foods eaten
In the 1997 NDNS (Gregory et al. 2000), there was a comparatively large range of foods that were less likely to have been consumed by young people from less advantaged households. Semi-skimmed milk was less likely to have been drunk by boys from households with low income, or in receipt of benefits and by boys from manual households. Seventy-two per cent of boys from households with a gross weekly income of less than £160 drank whole milk and 43% drank semi-skimmed milk, compared with 45% and 66%, respectively, of boys from households with a gross income over £600 per week. It is not yet known whether this trend has changed over the intervening decade.
The types of meat eaten showed little variation with socio-economic status (SES), although bacon and ham were less likely to have been eaten by boys from the lowest income households. Boys and girls from less advantaged households were also less likely to have eaten a number of types of fruit and vegetables, including raw carrots and other raw and salad vegetables, citrus fruits and fruit juice (Fig. 3).
The LIDNS report (low-income families) compared findings with data from the 1997 NDNS (general population, including low income) and found that there were some differences between the two reports (see Box 1).
There were some regional differences in the 1997 NDNS (Gregory et al. 2000) in the types of foods eaten. Boys and girls in Scotland were less likely to have eaten various types of vegetables. During the 7-day recording period, only 20% of boys in Scotland ate green leafy vegetables, a third ate raw or salad vegetables and 30% ate cooked carrots, compared with 50%, 53% and 53%, respectively, of boys in London and the South East. Chocolate confectionery was more likely to have been eaten by boys in Scotland (94%) compared with their counterparts in London and the South East (82%).
In Northern England, boys were less likely to have eaten beef/veal, lamb and liver than boys in the other regions, whereas girls in this region were more likely to have eaten beef/veal and dishes made from these than girls in London and the South East. Both boys and girls in Northern England were more likely to have consumed standard soft drinks than children elsewhere. Compared with girls in London and the South East, girls in the North of England were more likely to have eaten polyunsaturated margarine and, compared with girls in Scotland, they were more likely to have consumed polyunsaturated reduced fat spreads.
Box 1: Differences in average food consumption over seven days between children in the Low Income Diet and Nutrition Survey (LIDNS) report (low-income families) compared with children in the 1997 National Diet and Nutrition Survey (NDNS) report (general population)
Lower consumption by children in LIDNS compared with 1997 NDNS:
- • Wholemeal bread (girls 24 g vs. 42 g)
- • Buns, cakes and pastries (boys 121 g vs. 166 g; girls 98 g vs. 135 g)
- • Semi-skimmed milk (boys 634 g vs. 798 g; girls 447 g vs. 524 g)
- • Skimmed milk (boys 9 g vs. 33 g; girls 11 g vs. 39 g)
- • Vegetables (boys 318 g vs. 346 g; girls 380 g vs. 411 g)
- • Fruit (boys 321 g vs. 366 g)
- • Fruit juice (boys 329 g vs. 380 g)
- • Carbonated soft drinks (diet) (boys 347 g vs. 457 g; girls 339 g vs. 453 g)
Higher consumption by children in LIDNS compared with 1997 NDNS:
- • Pizza (boys 163 g vs. 112 g; girls 107 g vs. 73 g)
- • Whole milk (boys 873 g vs. 632 g; girls 620 g vs. 501 g)
- • Fat spreads (boys 86 g vs. 52 g; girls 71 g vs. 43 g)
- • Beef, veal, lamb and pork and dishes (boys 309 g vs. 240 g; girls 282 g vs. 199 g)
- • Processed meats (boys 449 g vs. 369 g; girls 385 g vs. 280 g)
- • Oily fish and canned tuna (boys 31 g vs. 24 g; girls 31 g vs. 28 g)
- • Non-carbonated soft drinks (not diet) (boys 1652 g vs 913 g; girls 1342 g vs. 755 g)
- • Carbonated soft drinks (not diet) (boys 1693 g vs. 1136 g; girls 1123 g vs. 856 g)
Although there were some regional differences in the types of foods eaten in the 1997 NDNS, there were few significant differences in mean energy intake or protein, carbohydrate and alcohol intake. Overall, intakes of most vitamins and minerals tended to be lower in Scotland and, to a lesser extent, in the northern regions of England compared with other regions. Even after adjusting for energy intake, lower intakes of vitamin D, iron and manganese in boys, and folate and pantothenic acid in girls still remained in Scotland and in the North of England. Also, lower intakes were still prevalent after adjustment for energy intake for iron and manganese in girls and for zinc in both sexes.
Differences in nutrient intakes between regions were more marked when analysed against SES, as indicated by receipt of benefits, household income and social class in the 1997 NDNS. Although, overall, there was no difference in total energy intake, there were differences in energy intake among boys, depending on whether or not their parents were in receipt of benefits (7.22 MJ compared with 8.27 MJ per day). Children from households in lower-income groups and those from households in receipt of benefits were significantly more likely to have lower mean intakes of protein, total carbohydrate, NMES and NSP than those from other households (Gregory et al. 2000).
With regard to total fat intakes, no socio-economic differences were found, but when expressed as a percentage of energy, it was found that the diets of boys (but not girls) from manual social classes contained more cis monounsaturated and polyunsaturated fatty acids than those from non-manual backgrounds.
Vitamin C intakes were significantly lower in both boys and girls from lower socio-economic backgrounds, even after adjusting for energy intake. Average intakes of all minerals, with the exception of iron, were significantly lower among boys, but not girls, in households in receipt of benefits. These differences in intakes persisted for calcium in boys and calcium, phosphorus and iodine in girls, even after adjusting for energy intake (Gregory et al. 2000).
Blood levels of vitamin C and folate were lower in Scotland and Northern England than elsewhere; this is likely to be linked to intake of fruit and vegetables. Girls in London and the South East had higher iron stores than in any other region and girls from the Northern region of England had the lowest plasma vitamin C levels. Lower nutritional status was found in the lower socio-economic groups for folate, vitamin C, vitamin D and iron (Gregory et al. 2000).
Alcohol, smoking and drug use
Alcohol intake and drinking habits
Over the last decade, concern about alcohol consumption in the UK has mounted, particularly in relation to consumption among children and young people. A report published by the Department of Health reported that, since 1990, the amount of alcohol consumed by those 11-to-15-year-olds who drink has doubled and the number of children admitted to hospital as a direct result of their alcohol consumption has increased. By age 15 years, the vast majority of 15-year-olds in England have had their first alcoholic drink. Altogether, 2.85 million of 11-to-17-year-olds have ever consumed an alcoholic drink, and over 1 million who do so on a weekly basis. Consumption by young people is greater in the UK than in many other European countries (Department of Health 2009).
In the new NDNS Rolling Programme (Bates et al. 2010) children are also asked about their experience of drinking alcohol. Table 12 shows the proportion of children who reported ever having had a ‘proper’ alcoholic drink (i.e. not just a taste).
|8–10 years||11–12 years||13–15 years|
Among those aged 13-to-15-years, 3% of boys and 1% of girls reported drinking alcohol about twice a week, 1% of boys and 11% of girls about once a week, 8% of boys and 2% of girls about once a fortnight, and 16% of boys and 12% of girls about once a month. The rest reported drinking alcohol only a few times a year or that they never drink. Nobody reported drinking almost every day. In younger age groups, those who reported drinking alcohol said they did so only a few times a year.
Data from the food diaries showed that, on average, 1.5% of total energy intake came from alcohol in boys and 0.8% in girls aged 11-to-18-years. The contribution of alcohol to total energy intake in alcohol consumers was 8.2% and 4.6%, respectively, in girls and boys aged 11-to-18-years (Bates et al. 2010).
Smoking and drug use
Other lifestyle factors impacting on nutritional status include smoking and drug use. A survey of smoking, drinking and drug misuse among young people in England (NHS 2009) collected information from 7798 pupils aged 11-to-15-years throughout England in autumn 2008. Smoking had been tried at least once by 32% of the sample; 6% smoked regularly compared with around 12% during the mid 1990s. Girls were more likely to smoke than boys, and the prevalence of smoking was reported to increase with age (14% of 15-year-olds smoked once a week compared with 0.5% of 11-year-olds). A survey in Scotland reported 4% of 13-year-olds to be regular smokers, rising to 15% of 15-year-olds (NHS Scotland 2009). As in England, there has been a dramatic decline in the prevalence of childhood smoking in Scotland since peak levels in 1996 and 1998.
The National Health Service (NHS 2009) report suggests drug use has declined, with 22% of pupils in schools reporting that they ever took drugs in 2008, compared with 29% in 2001 (NHS 2009). Cannabis was found to be the most frequently used drug in both surveys. Information from the NHS 2009 survey suggested that 3.6% of pupils had taken Class A drugs in the year before the survey, which had remained at a similar level since 2001.
3 Physical activity in schoolchildren
The level of physical activity, its frequency, duration, intensity, type and total amount, as well as the time spent sedentary have a major impact on health at all stages of life. There is concern that many children spend too much time undertaking sedentary activity (see ‘Sedentary behaviour’ at the end of this section). Physical inactivity has been identified as the fourth leading risk factor for global mortality (6% of deaths globally). This follows high blood pressure (13%), tobacco use (9%) and high blood glucose (6%). Overweight and obesity are responsible for 5% of global mortality (WHO 2010). Being physically active in early life is of particular importance as it impacts not only on current health status but can also influence health in later life. The many benefits for children and young people of being physically active include helping to maintain energy balance and therefore a healthy bodyweight; aiding bone and musculoskeletal development; reducing the risk of diabetes and hypertension; as well as numerous psychological and social benefits (including improved psychological wellbeing, and higher self-confidence and self-esteem) (see Miles 2007). These health benefits will be explored in more detail in Section 4; this section focuses on physical activity recommendations, on how much physical activity children in the UK are actually doing, and on the factors that influence physical activity levels.
Physical activity is defined as ‘any bodily movement produced by skeletal muscles that requires energy expenditure’ (WHO 2010). It therefore includes activities ranging from organised sport and exercise, to active play (running around outside) or activities undertaken as a part of everyday living (i.e. walking or cycling to school, housework). Physical activity can take a number of forms and types, such as moderate or vigorous intensity, or activities that convey particular benefits, e.g. aerobic or weight bearing activities that benefit the cardiovascular system and skeleton, respectively (see Miles 2007).
Recommendations in the UK
Within the UK, physical activity recommendations have existed in England, Scotland and Wales for more than a decade. Although recommendations for children have been similar in the different areas of the UK (no recommendations in Northern Ireland), there have been slight differences in both the amount and type of activity recommended. For the first time now, UK-wide guidelines on physical activity are available (Department of Health 2011). The new guidelines, which now also include recommendations for pre-school children, were published by the Chief Medical Officers from the four home countries in July 2011. The recommendations for children and adolescents aged 5-to-18-years are presented in Table 13.
|1. All children and young people should engage in moderate to vigorous intensity physical activity for at least 60 minutes and up to several hours every day.|
|2. Vigorous intensity activities, including those that strengthen the muscle and bone, should be incorporated at least three days a week.|
|3. All children and young people should minimise the amount of time spent being sedentary (sitting) for extended periods.|
The new guidelines mainly differ from the old guidelines of the UK countries in terms of intensity of physical activity, and for the first time a recommendation about limiting physical inactivity is made.
Moderate intensity activity can broadly be defined as that which raises the heart rate and leaves an individual slightly out of breath, but still able to talk, whereas somebody doing vigorous intensity activity will breath very hard, be short of breath, have a rapid heart beat and will not be able to carry on a conversation comfortably. The recommended amount of physical activity can be made up of smaller bursts of activity, which reflects the typical activity patterns of children (i.e. walking to school, spontaneous play, as well as structured activity such as Physical Education (PE) lessons). Variety is important at this age: moderate to vigorous bouts of activity will benefit the cardio-respiratory system; activities to improve bone health are those which produce high physical stress on the bones, and include running, jumping and skipping; active play (e.g. climbing, carrying and ‘rough and tumble’) helps to improve muscle strength and flexibility.
Measuring physical activity
Assessment of physical activity levels may be carried out using subjective or objective measurements. Subjective methods typically take the form of questionnaires asking about current or past activity levels, including physical activity diaries, logs and recall surveys. Objective methods use physiological measures, such as heart rate monitoring or motion sensors, which provide real-time estimates of the frequency, intensity and duration of physical activity (Miles 2007).
Accurate identification of children's physical activity levels by means of subjective methods is made difficult by both the type of exercise children undertake and their cognitive ability to recall physical activity. Whereas adult activity is more likely to include exercise (a subcategory of physical activity, usually planned, structured and performed to improve physical fitness), children's activity tends to be far more sporadic. An inability to recall past events accurately in younger children further compounds this problem (Livingstone et al. 2004). More objective methods generally provide more accurate data in children, but the use of these methods is associated with higher cost and burden on subjects compared with subjective assessment methods. Therefore, despite the limitations of subjective assessment of children's physical activity levels (either by children or their parents), this approach is commonly used in large-scale epidemiological studies because it is a relatively inexpensive, quick and simple way to obtain data. However, there has been an emergence of studies opting to use objective assessment methods to identify activity levels, often in a subsample in addition to subjective methods (e.g. used in the 2008 Health Survey for England). Tools used can range from simple pedometers, which count steps taken, to more sophisticated accelerometers, which record detailed information about activity patterns on a minute by minute basis.
Current activity levels of children across the UK
The 2008 Health Survey for England assessed levels of out-of-school physical activity (any activity outside school lesson time) in children (aged 2-to-15-years) using both self-reporting and accelerometers (Craig et al. 2009b). Data from self-reported questionnaires suggest that 32% of boys and 24% of girls met the previous physical activity target (at least 60 minutes of at least moderate intensity physical activity each day). However, as only out-of-school activity was assessed, this is likely to be an underestimation of actual activity. The numbers were considerably lower than the 72% of boys and 63% of girls who were reported to meet the previous target in the 2007 survey (also only out-of school physical activity) (Craig & Shelton 2008); this can partly be explained by major revisions of the questionnaire used in order to obtain more accurate data (Craig et al. 2009b). Changes in the new questionnaire included questions about sedentary time and separate questions on physical activity during break time and travel. The validity and reliability of earlier questionnaires were unknown (Craig et al. 2009b). Levels of physical activity varied with age (Fig. 4); among girls, there was a downward pattern in activity associated with increasing age, with the proportion meeting the previous government recommendations ranging from more than 30% in those aged 5 years to only 12% among those aged 14 years. Accelerometer data suggested similar activity levels to those obtained by self-reporting, with 33% of boys and 21% of girls meeting previous government recommendations (Craig et al. 2009b). The findings from the government's Health Survey for England are in stark contrast to other studies assessing physical activity levels of children in England using accelerometry, some of which have suggested just 2.5% of children may meet previous government recommendations (Riddoch et al. 2007).
The 2009 Scottish National Health Survey, using self-reported methods to assess out-of-school activity, found that 69–72% of boys and 56–60% of girls in Scotland met the previous recommendation of at least one hour of moderate activity. When activity undertaken at school was included, 75–77% of boys and 64–68% of girls met the recommendations (Bromley et al. 2010). The large differences between England and Scotland can, in large part, be explained by the use of a revised questionnaire in the 2008 Health Survey for England, whereas the Scottish Health Survey used a questionnaire based on the physical activity questionnaire used in earlier Health Surveys for England, which reported similar values to the Scottish survey (Craig & Shelton 2008; Craig et al. 2009b; see earlier).
The Welsh Health Survey 2009 reported that 47% of boys and 29% of girls were physically active (physical activity that left the child feeling warm or slightly out of breath) for at least 1 hour everyday, and 63% of boys and 45% of girls were physically active on at least 5 days a week – this included physical activity at school (Welsh Assembly Government 2010). Northern Ireland does not have a comparable health survey. However, research has indicated that physical activity levels are low, with just 15% of 8-to-12-year-olds taking part in 60 minutes of activity, which ‘made them out of breath or hot and sweaty’ everyday (Central Survey Unit 2008).
Influences on children's physical activity levels
Many factors influence children's physical activity habits and understanding these is the key to ensuring all children meet national recommendations. This is particularly important as research indicates that physical activity behaviours may track into adulthood (Malina 1996; Harro & Riddoch 2000) and, therefore, facilitating physical activity in childhood may be important in helping set good behaviour early on.
Gender and age
That boys are more active than girls is a common observation and evidence to support this is provided by a number of studies in school-aged children (Inchley et al. 2005; Henning Brodersen et al. 2007; Riddoch et al. 2007). In addition to gender, age is also found to affect activity levels, with the majority of research indicating that activity levels decline as children get older. In the Health Behaviour in Teenagers Study, the number of days of vigorous physical activity per week fell over the 5-year study period, and more so in girls than in boys. In contrast, hours of sedentary behaviour increased over the study period by an average of 2.5 hours per week in boys and 2.8 hours per week in girls (Henning Brodersen et al. 2007). A series of studies in Scotland found that there was a consistent decrease in physical activity in girls with increasing age but no consistent trends could be observed in boys (Inchley et al. 2005; Bromley et al. 2010). In the 2008 Health Survey for England, no clear pattern was obvious in boys, but among girls, there was again a reduction in activity associated with increasing age (Craig et al. 2009b).
Henning Brodersen et al. (2007) explored the effect of ethnicity on physical activity levels. Ethnicity was classified, by self-reporting, as either White, Black or mixed Black, or Asian or mixed Asian. Asian students of both sexes reported being less physically active than their White counterparts (P < 0.001), whereas for Black students, lower activity levels were seen only among Black girls when compared with White girls. However, Black students of both sexes reported higher levels of sedentary behaviour than their White peers, the difference being greater in girls. Trends in sedentary behaviour also differed in White and Asian girls, with increasing sedentary behaviour occurring at younger age in Asian girls (Henning Brodersen et al. 2007).
The 2004 Health Survey for England's report on the Health of Minority Ethnic Groups also showed that with the exception of Pakistani boys and Irish boys and girls, children in minority ethnic groups are less likely to perform 60 minutes of activity per day than the general population, although considerable differences between different minority ethnic groups were seen. Additionally, in most groups, girls were less likely than boys to have achieved a high level of activity in the week prior to the interview. The difference was particularly large in the Black African, Pakistani, Bangladeshi and Indian group, and in Black Caribbean and Irish children it was similar to children of the general population (see Fig. 5). Only in the Chinese group were girls as likely as boys to have achieved a high level of activity (Sproston & Mindell 2006).
Socio-economic Status (SES)
In the Health Behaviour in Teenagers Study no association between SES and physical activity was found in boys, but girls from lower SES households were less active than those from higher SES households. Sedentary behaviour levels were greater in boys and girls from low socio-economic neighbourhoods, the difference being greater in girls than boys (Henning Brodersen et al. 2007). The Low Income Diet and Nutrition Survey (LIDNS) provides information on the diet and lifestyle habits of people on low income in the UK, and involved 3728 people (932 children 2-to-18-years) from 2477 households from the lowest 15% of the population in terms of material deprivation. The survey found that 28% of boys and 34% of girls aged 2-to-15-years reached the previously recommended level of 60 minutes of moderate physical activity per day (excluding activities at school). This is clearly lower than the respective percentages in the 2003 Scottish Health Survey[74% of boys and 63% in girls; (Bromley et al. 2005)] and the 2002 Health Survey for England[70% boys and 61% girls; (Sproston & Primatesta 2003)], which used an identical questionnaire to assess physical activity levels. Inchley et al. (2005) also suggested that children from low-income backgrounds are less active than their counterparts from higher income families. Data on physical activity levels in different socio-economic groups are however inconsistent. In contrast to the data referred to above, data from the 2008 Health Survey for England found that more boys and girls in the lowest family income quintile met the government's physical activity recommendations than those in the highest income quintile (36% for boys and 30% for girls in the lowest income families, versus 25% for boys and 22% for girls in the highest) (Craig et al. 2009b). Data from the Scottish Health Survey 2009 showed no significant association between boys' physical activity levels and SES, but found a significant association for girls, with more girls from families of lower SES meeting the recommendations compared with girls from families of higher socio-economic backgrounds (Bromley et al. 2010). It is unclear why there are such discrepancies in the data. Research has suggested that the type of activity may also differ, with children from lower socio-economic background tending to participate in unstructured activities, or free play, while children from higher SES groups are more likely to take part in sports in clubs and structured activities (Brockman et al. 2009).
Family and peer influence
The role of family, in particular parental support, in influencing children's activity levels has received increasing attention in recent years. However, the extent of parental and peer influence is still uncertain.
Parents can potentially encourage activity by role modelling, providing support or by facilitating activity, such as providing transport or financial support. A study in 180 9-year-old girls examined the extent to which parents' activity-related parenting practices influenced the girls' physical activity levels (Krahnstoever Davison et al. 2003). In families where both parents provided a high level of overall support for their daughter's activities, 70% of girls were classified as being highly active, compared with 56% in families where only one parent showed a high level of overall support and 32% of girls in families in which neither parent provided a high level of overall support. The type of support given differed between fathers and mothers; fathers supported their daughters more through role modelling, whereas mothers acted more as facilitators by providing logistic support; the impact of both kinds of support on girls' activity levels seemed to be similar (Krahnstoever Davison et al. 2003). In another study, parent inactivity was a strong and positive predictor of child inactivity, whereas scores of parent activity were somewhat weaker predictors of a child's vigorous activity and total physical activity level (Fogelholm et al. 1999). A study by Brockman et al. (2009) found that SES of the family may influence the level and type of support given. Children from schools in middle/high SES areas were more assisted through actions such as logistical and financial support, while parents of children from schools in low SES areas (lowest third of SES status defined by the Index of Multiple Deprivation, a UK government-produced measure of deprivation) mainly restricted their input to verbal encouragement and demands on the children (e.g.‘Get off the sofa and go and play’). Participation in family-based activities was reported to be higher in children from schools in middle/high SES areas than children from schools in low SES areas. Cost was reported as a significant barrier by children from schools in low SES areas (Brockman et al. 2009). The Scottish and English health surveys also looked at the relationship between parents' physical activity levels and physical activity levels of their children, resulting in different outcomes. In the 2008 Health Survey for England (Craig et al. 2009b), younger boys (2-to-10-years) were more likely to meet the recommendations if the parents met the recommended level of physical activity, whereas in older boys (11-to-15-years) only the fathers' activity levels seem to have an influence. Among girls, the activity level of parents made relatively little difference to the proportion meeting the recommendations. Similarly, for both age groups of boys and girls, more were in the low activity category if their parents were also in this category (Craig et al. 2009b). In the Scottish Health Survey, both boys and girls whose mothers met physical activity recommendations were more likely to meet the recommendations themselves, whereas this pattern was not apparent in relation to the fathers' physical activity levels (Bromley et al. 2010). More research will be needed to understand these discrepancies between studies.
A study carried out in a cohort of 315 9-to-13-year-olds from schools across London sought to determine peer (friends') influence on physical activity levels. Activity levels were recorded using a 3-day diary and pedometer. Peer influence was assessed using a Social Support and Eating Habits/Exercise Survey. The study found there to be a significant correlation between number of steps taken and friends taking part in physical activity or exercise with the study subject, and friends discussing physical activity or exercise with the subject (Finnerty et al. 2010). The role of peers in influencing activity levels is also described by Jago et al. (2009) who suggest that promoting physical activity via friendship groups may be one way to increase activity levels among children (Jago et al. 2009).
The environment in which we live has received increasing attention over recent years in terms of the role it plays in influencing physical activity levels of individuals. The characteristics of the built environment are often cited as a cause of inactivity. In particular, an increasing reliance on car use in place of walking and cycling, concerns over safety, and a lack of green space are commonly cited as barriers to being physically active (Dunton et al. 2009). Indeed, busy traffic and a neglect of local play areas have both been identified as barriers to children's participation in physical activity (Brunton et al. 2003). However, a recent systematic review comparing the physical activity levels of children living in different built environments did not find major differences between children from rural and urban areas (Sandercock et al. 2010).
In 2008, the National Institute for Health and Clinical Excellence (NICE 2008) issued evidence-based guidance on how to promote physical activity by creating built or natural environments which support active lifestyles. The guidance features advice such as:
- • ‘ensure planning applications for new developments always prioritise the need for people (including those whose mobility is impaired) to be physically active as a routine part of their daily life;
- • ensure pedestrians, cyclists and users of other modes of transport that involve physical activity are given the highest priority when developing or maintaining streets and roads (this includes people whose mobility is impaired).’
Implementation of such advice will help to ensure a child's environment offers plenty of opportunity to be active, including ensuring children can participate in physically active play.
Travel to school
Mode of travel to school may be associated with physical fitness in schoolchildren, as suggested by findings from the East of England Healthy Hearts study. Based on data from 6085 schoolchildren aged 10-to-16-years, those walking or cycling to school were significantly more likely to be classified as ‘fit’ compared with children using passive travel modes (car or public transport). This significant difference remained after adjusting for general physical activity levels in girls, but not in boys (Voss & Sandercock 2010).
Sedentary behaviours refer to activities that do not increase energy expenditure substantially above the resting level; these include screen-based behaviours such as TV viewing and playing computer games, as well as activities such as reading, listening to music, sitting and lying down (Pate et al. 2008; British Heart Foundation 2009). It has been suggested that not only low physical activity levels but also increasing time spent on sedentary activities may be linked to the increase in overweight and obesity (Biddle et al. 2004). However, based on current evidence, some experts conclude that it is difficult to establish a clear link between sedentary behaviour and overweight and obesity. It has been suggested that this is more likely to be a result of a lack of evidence rather than because there is no link (Biddle et al. 2004; Reilly 2008), and that despite the lack of firm evidence there are good reasons for believing that physical inactivity is causally related to obesity in children (Biddle et al. 2004). Those suggesting that there is an association between sedentary behaviour and obesity say it may be complex; it may not be as simple as sedentary behaviours directly displacing physically active ones. It has been proposed that inactivity may be independently associated with Body Mass Index (BMI, see Section 4.1) irrespective of physical activity levels (Fleming-Moran & Thiagarajah 2005). More evidence is needed in order to draw firm conclusions.
In addition, an increase in sedentary behaviour may not just mean fewer calories are expended; evidence indicates that activities such as television viewing are often associated with negative eating habits, including the consumption of energy dense foods and drinks (Vereecken et al. 2006; Reilly 2008), thereby exacerbating the problem. Evidence from intervention studies in children show that decreasing sedentary behaviour results in improvement in weight parameters, although the magnitude of change is modest and difficult to interpret (DeMattia et al. 2007). There is a need to understand whether tackling sedentary behaviour in public health intervention programmes will be effective in reducing overweight and obesity in children.
The 2008 Health Survey for England examined sedentary time (excluding at school) in children and reported that boys and girls spend an average of 3.4 hours on weekdays and 4.1 hours on weekend days being sedentary (excluding school or sleeping time), with the average time increasing with age (Craig et al. 2009b). A further study on sedentary behaviour in 923 teenage girls (12-to-17-years) from secondary schools in 15 regions within the UK reported that the five most time-consuming sedentary activities occupied on average 4.4 hours per weekday and 6.7 hours per weekend day. This is in contrast to just 44 minutes per weekday and 53 minutes per weekend day devoted to active transport or sports and exercise (Gorley et al. 2007).
The new UK physical activity guidelines include recommendations on physical inactivity. All children and young people are advised to minimise the amount of time spent being sedentary (sitting) for extended periods (Department of Health 2011). In the US, the National Association for Sport and Physical Education advises that children should try to avoid being inactive for periods longer than 2 hours (Corbin & Pangrazi 2004).
4 Nutrition, physical activity and health in childhood
4.1 Overweight and obesity
Classification of overweight and obesity
In both adults and children, appropriate weight-for-height is most frequently described using the BMI, determined by dividing weight (kg) by height squared (in metres). For adults cut-offs for overweight and obesity are 25 and 30 kg/m2, respectively (WHO 2000). These cut-offs are not applicable to children because the ratio of velocity of weight gain to that of height gain changes during normal growth, especially around puberty. For example, the BMI of a boy or girl on the 50th centile at age 1 years is 17 kg/m2, then falls to 15.5 kg/m2 at age 6 years and climbs to 21 kg/m2 at age 20 years (Cole et al. 2000). Therefore, age- and sex-specific reference data (centile cut-off points on charts) are necessary to interpret measurements of children. For children in the UK, national reference data for child-specific BMI are available; these are based on a large representative sample of UK children from 1990 (Cole et al. 1995). These reference values are widely used to assess the weight status of children, and are considered by the Growth Reference Review Group, a working group convened by the Royal College of Paediatrics and Child Health, to be the only suitable BMI reference for assessing weight relative to height in children for clinical purposes (Wright et al. 2002). In clinical practice, children above the 91st centile are classed as overweight and children above the 98th centile as obese (Reilly et al. 2002; Wright et al. 2002). However, in public health settings different cut-off points are generally used. The 85th percentile as the cutoff for overweight and the 95th percentile as the cutoff for obesity are used by both the Health Survey for England and the National Child Measurement Programme, a governmental initiative to measure children in Reception (aged 4-to-5-years) and Year 6 (aged 10-to-11-years) to assess overweight and obesity levels (Department of Health 2008; Craig et al. 2009a).
The 85th and 95th percentiles are also used as cut-off points for overweight and obesity in the growth references by the World Health Organization (WHO) for school-aged children and adolescents (De Onis et al. 2007), which are based on data from two large surveys, the Health Examination Survey (European) and the Health and Nutrition Examination Survey (US). The references were aligned with the growth reference standards for children up to 5 years of age and with the BMI cut-off points for overweight and obesity in adults (De Onis et al. 2007). The International Obesity Task Force (IOTF) has also put forward an alternative derived from data collected among children from six countries. The IOTF identifies the childhood percentile in the dataset corresponding to a BMI of 25 or 30 at age 18 (Butland et al. 2007). These growth references are useful for international comparison of overweight and obesity in children. However, for studies on the prevalence of overweight and obesity in the UK, the standards based on a sample of UK children are generally still the preferred choice and are being used in various health surveys as mentioned above.
Prevalence of overweight and obesity
The Health Survey for England provides data on trends of overweight and obesity in children throughout England from 1995 to 2009. In this survey, overweight was defined as a BMI between the 85th and 95th percentiles, and obesity was defined as a BMI above the 95th percentile (Craig & Hirani 2010b). Prevalence rates of overweight and obesity in 2-to-15-year-old children in England in 2009 compared with 1995 are shown in Table 14.
|2–10 years||11–15 years||2–10 years||11–15 years|
Table 14 and Figures 6 and 7 show that the increase in overweight and obesity between 1995 and 2009 was mainly due to increasing obesity rates and the overweight rates remained relatively stable. In girls, this trend is observed to a somewhat lesser degree than in boys. In both girls and boys, the rates of overweight and obesity seem to have levelled in the past few years, although there was a peak in 2008 in boys aged 11-to-15-year (Craig & Hirani 2010a). Mean BMI in girls is associated with household income, with BMI increasing with decreasing income and those in the highest income quintile being the least likely to be obese. No clear trends were found for boys (Craig et al. 2009b; Craig & Hirani 2010b).
Another source of data on overweight and obesity in children living in England is the school-based National Child Measurement Programme, which records height and weight of children aged 4-to-5-years and 10-to-11-years; the programme started in the school year 2006/2007. In contrast to the Health Survey for England, where a sample of children representative of the population are measured, in this programme all children in Reception and Year 6 classes are measured. The programme uses the same cut-off points as the Health Survey for England. Data from the latest report from school year 2009/10 (Table 15) show that obesity rates are higher in boys than girls and clearly increase (almost double) between Reception and Year 6, in both boys and girls (Department of Health & Department for Children Schools and Families 2010).
|Overweight (%)||Obese (%)|
|Reception (age 4–5 years)||Boys||13.9||10.5|
|Year 6 (age 10–11 years)||Boys||14.6||20.4|
The Scottish Health Surveys use the same cut-off points and reference values as the English surveys to define overweight and obesity in children. Data from 2009 presented in the latest report (Bromley et al. 2010) are shown in Table 16.
|2–6 years||7–11 years||12–15 years|
Figure 8 shows that whereas the percentage of girls in Scotland who are overweight or obese has not changed considerably over the period 1998–2009, there are fluctuations in the total prevalence of overweight and obesity in boys aged 7-to-15-years. There has been a notable difference between the years 2008 and 2009, which the authors of the study suggest may reflect sample fluctuation rather than a true population difference. However, it is still clear that there has been an increase in the prevalence of overweight (including obesity) over the past years in boys aged 7-to-15-years in Scotland, whereas younger boys show a decline in the prevalence of overweight (including obesity).
Data from the Welsh Health Survey 2009 show that 15% of boys aged 2-to-15-years were overweight and a further 20% were obese, and 15% of girls were overweight and 18% obese (Welsh Assembly Government 2010). There were no obvious trends in the prevalence of overweight and obesity between 2007 and 2009 (Fig. 9).
Prevalence data for overweight and obesity in Northern Ireland are available from measurements made in the Northern Ireland Health and Social Wellbeing Survey in 2005/2006 (NISRA 2007). The survey found that, based on UK national BMI percentiles, 18% of children aged 2-to-15-years were obese (20% of boys and 15% of girls). The levels of obesity in boys were generally higher than in girls (Fig. 10).
Obesity and ethnicity Child obesity prevalence has been shown to vary substantially between ethnic groups, with obesity prevalence generally being lower in children of White British ethnicity. Data from the National Child Measurement Programme showed obesity prevalence to be especially high among children of both sexes from Black African and ‘Black Other’ ethnic groups, and among children from some Asian groups, particularly boys of Bangladeshi, Pakistani and ‘Asian Other’ ethnicity (Department of Health & Department for Children Schools and Families 2009). Also, the 2004 Health Survey for England found differences in obesity levels between ethnic groups, with prevalence rates in boys ranging from 14% in Indian and Chinese ethnic groups to 31% in the Black African group. In girls, the rates ranged from 12% in the Chinese ethnic group to 27% in the Black Caribbean and Black African groups (Sproston & Mindell 2006). The National Obesity Observatory has summarised UK data on overweight and obesity in ethnic groups in the UK in a recent report (see Gatineau & Mathrani 2011).
Future trends in children The Foresight Report on obesity (Butland et al. 2007), produced by the UK government's Foresight Programme, published projections on future obesity trends in children. In this report, the cut-offs suggested by the IOTF were used to define overweight and obesity as this allows international comparison (see page 318). The IOTF cut-offs were applied to data from the Health Surveys for England and were used for projecting future trends (see Table 17). Significant increases in levels of obesity, particularly in boys, are expected should current trends not be halted or reversed. Taking the proportion of overweight young people into account, Foresight's extrapolations suggest that, by 2050, 70% of girls and 55% of boys could be overweight or obese (Butland et al. 2007).
|All under 20 years||8||15||25|
|All under 20 years||10||15||25|
Factors involved in the development of childhood obesity
Obesity is a complex condition and a variety of factors contribute to rising obesity levels in children and adolescents. Obesity occurs when energy intake remains higher than energy expenditure, for an extended period of time (Prentice 1999; Moreno & Rodriguez 2007). This means that more energy from food and drinks than the body uses has been consumed over a period of time and, in order to halt weight gain or lose weight, either less energy from food and drinks needs to be eaten or more energy needs to be used by increasing the level of physical activity, or a combination of both. However, in reality, obesity has contributing factors on a variety of levels. Human biology, eating and physical activity behaviours, people's beliefs and attitudes, and broader economic and social drivers all have a role to play in determining obesity (Butland et al. 2007). Environmental factors such as the ready availability of energy dense foods and drinks and limited opportunities for being physically active can contribute to the development of overweight and obesity; this is often referred to as an ‘obesogenic environment’. The pattern of growth during early life is also a determinant of future risk of obesity. There is evidence that weight gain in early life, particularly catch-up growth in low-birth-weight babies, is associated with a higher risk of overweight and obesity in later life. Also an early so called ‘adiposity rebound’ in childhood (the period of time in early childhood when the bodyweight for height falls and then rises again) predicts a higher BMI later on (Butland et al. 2007).
To tackle an increase in obesity levels in children and adolescents, the various contributing factors need to be taken into account rather than simply addressing one factor.
Diet and physical activity Although it is clear that excess energy intake will result in weight gain, it is difficult to single out specific dietary factors that are related to weight gain. An extensive systematic review looking at evidence from epidemiological studies on associations between diet and physical activity and excess weight gain found no association between weight gain in children and intake of any of the macronutrients (fat, protein, carbohydrates) (Summerbell et al. 2009). There was no single food group, including beverages, that was associated with a higher risk of obesity in children. The authors also found no association between energy intake and weight gain or energy expenditure and weight gain. An inverse association between physical activity and sedentary behaviour, and weight gain and obesity was found in studies with objective measures of activity and inactivity, but no consistent associations were found in studies with more subjective measures (Summerbell et al. 2009).
The findings of this review are in contrast with the fact that a positive energy balance is needed in order to gain weight or become obese. This illustrates the complexity of the challenge faced in tackling obesity. It is possible that failure to show associations is the result of study limitations, including the use of self-reported data that may under-report weight, overestimate height, overestimate activity levels and introduce imprecision in the measurements of the other relevant factors (Summerbell et al. 2009).
Portion size and energy density It has been shown that presenting children with larger portions leads to an increased intake of the respective food, but also to an increased food and energy intake overall (see Benelam 2009). However, this effect was not found in very young children (3 years or younger), where increasing portion size does not seem to lead to an increased food intake (Fisher & Kral 2007; Benelam 2009). One study looked at the effect of increasing portion size as well as the energy density of an entrée presented to children aged 5-to-6-years on total food and energy intake of one whole meal. In accordance with earlier findings, the authors found an increased food intake when children were presented with a larger portion size, but did not find any influence of energy density on the total amount of food consumed during the meal (Fisher et al. 2007). This suggests that children do not compensate for the higher energy density by eating a smaller portion, which in turn can lead to an overall higher energy intake if energy dense foods are consumed regularly.
Research so far does not suggest that the tendency to overeat when large portions are presented is specific to overweight children (Fisher & Kral 2007).
Sugar-sweetened beverages The consumption of sugar-sweetened beverages (including carbonated drinks and fruit drinks) has increased alongside increases in obesity prevalence, particularly in the US, leading to speculations that these drinks may be partly responsible for the obesity epidemic (Malik et al. 2006). The evidence on the effect of sugar-sweetened beverages on bodyweight and body fat, however, seems to be inconclusive (see Benelam & Wyness 2010). A systematic review looking at cross-sectional, prospective cohort and experimental studies concluded that there was an association between the consumption of sugar-sweetened drinks and weight gain, although the authors pointed out that there are confounding factors that may have biased the results as certain lifestyle behaviours may cluster (Malik et al. 2006). A more recent meta-analysis of evidence from prospective cohort and experimental studies in children and adolescents found no association between intake of sugar-sweetened beverages and BMI (Forshee et al. 2008).
It has been suggested that caloric liquids could lead to excess energy consumption because they fail to trigger satiety compared with equivalent energy intakes from solid food. However, a review of the literature concluded that studies comparing the effects of equivalent amounts of liquid or solid energy on satiety have yielded inconsistent results and do not consistently support the hypothesis that liquid calories go undetected by appetite control systems (Drewnowski & Bellisle 2007).
Meal frequency, snacking, breakfast The systematic review by Summerbell et al. (2009) looked at evidence from prospective cohort studies on frequency of eating/snacking and eating/skipping breakfast in children and weight gain. The authors concluded that there was no epidemiological evidence of a consistent association between snacking or breakfast skipping and subsequent excess weight gain and obesity (Summerbell et al. 2009). Another systematic review also included cross-sectional, in addition to cohort, studies. The authors found that 13 out of the 16 included studies (the majority being cross-sectional) consistently showed a protective effect of eating breakfast against becoming overweight or obese; four studies that reported on the association between breakfast and BMI all found an increase in BMI in breakfast skippers (Szajewska & Ruszczynski 2010). However, the authors pointed out that as almost all of the data gathered in the systematic review were from observational studies, causality should not be assumed based on these findings.
In summary, there seems to be no single dietary or lifestyle factor that leads to overweight and obesity, but a variety of different often interlinked factors, as illustrated in the Foresight Report on Obesity (see Butland et al. 2007).
Health implications of overweight and obesity
Overweight and obesity are associated with an increased risk of various conditions, including cardiovascular disease, diabetes mellitus, high blood pressure and problems with the muscoskeletal system. Diseases such as heart disease or stroke typically occur in adulthood. However, obese children routinely have been shown to have many of the changes associated with vascular disease in adults, including insulin resistance, high blood pressure, elevated total cholesterol, triglycerides, LDL-C and oxidised LDL-C, and reduced high-density lipoprotein cholesterol (HDL-C) (Larson Ode et al. 2009; Short et al. 2009; Steinberger et al. 2009). Insulin resistance is the most common metabolic alteration related to obesity and obesity is the major risk factor for the development of insulin resistance in children and adolescents; it represents an important link between obesity and other metabolic as well as cardiovascular complications (Chiarelli & Marcovecchio 2008; Nathan & Moran 2008). It has been suggested to be a key risk factor in the development of lipid abnormalities; at the same BMI, adolescents with evidence of insulin resistance are more likely to have an abnormal lipid profile (Nathan & Moran 2008; Larson Ode et al. 2009). Recent evidence suggests that waist circumference in children is an independent predictor of insulin resistance (Chiarelli & Marcovecchio 2008; Nathan & Moran 2008; Steinberger et al. 2009). Considered previously to be a disease of adults, in the last decade, type 2 diabetes mellitus has become a far more common occurrence in children and adolescents. Depending on the ethnic composition of the population, between 8% and 50% of newly diagnosed adolescent diabetic patients have type 2 diabetes (Steinberger et al. 2009), the remainder being type 1 and other forms of diabetes.
Obese children have also been found to have a higher risk of impaired endothelial function, lower arterial compliance and elasticity, and increased intima-media thickness (Short et al. 2009; Steinberger et al. 2009), which are measures of vascular health and associated with adverse cardiovascular events in adulthood. Autopsy studies in children and adolescents have also shown that the extent of early atherosclerosis of the aorta and coronary arteries is directly associated with levels of lipids, blood pressure and obesity (Steinberger et al. 2009). Obesity is also a well-established risk factor for hypertension in children (Nathan & Moran 2008; Larson Ode et al. 2009).
In addition to the negative impact of obesity on factors associated with cardiovascular disease, multiple studies have suggested that childhood overweight and obesity track into adulthood (Steinberger et al. 2009; Biro & Wien 2010; Lloyd et al. 2010). Overweight children are more prone to becoming overweight adults, especially at higher BMIs or if they have obese parents (Steinberger et al. 2009; Biro & Wien 2010). Important evidence for this comes from a US study (the Bogalusa Heart Study) that began in 1972 and has followed many participants from childhood into adulthood; the outcomes of this study show that children who were overweight at age 2-to-5-years were over four times more likely to become obese than were those with a BMI < 50th percentile (Freedman et al. 2005). In this study, childhood triceps skinfold thickness, a measure of body fat, provided only a slightly stronger association with adult adiposity than childhood BMI (Freedman et al. 2005), which itself does not directly measure body fatness. A retrospective school-based cohort study that followed up 1520 men born between 1927 and 1956, from the age of 9-to-18-years, into adulthood (average 63 years) resulted in similar outcomes. Childhood BMI correlated strongly and positively with adult adiposity, as measured by BMI, waist and hip circumferences (Sandhu et al. 2006). Data from a UK cohort (Thousand Families Cohort Study, consisting of 1142 children born in 1947 and followed up into adulthood) showed a moderate, statistically significant correlation between childhood and adult BMI. At age 50 years, those who had been above the 90th centile for BMI at age 9 or 13 years were between five and nine times more likely to be obese than those in the thinnest quartile in childhood. The association between childhood BMI and adult percentage of body fat was weaker than that with adult BMI. Most of those in the top quarter for body fat aged 50 years had not been overweight as children: 94% had been below the 90th percentile for BMI at age 9 and 79% at age 13 (Wright et al. 2001). It has to be considered that around 50 years ago, overweight in children was not as common as today and it is likely that most children were of normal weight. The outcomes of this study indicate that although those who are overweight or obese in childhood have an increased risk of being overweight and obese as adults, thinness in childhood does not protect from overweight and obesity in adulthood.
Children who are obese are more likely to already have cardiovascular risk factors, including insulin resistance, lipid abnormalities and high blood pressure, and are more likely to be overweight and obese as adults. However, the question is whether childhood obesity is an independent risk factor of disease in later life. If it is, this would mean that being overweight at a young age automatically increases the risk of disease in adulthood, even if the weight status changes, and that thinness in childhood decreases the risk of disease in adulthood, even if people later become overweight in adulthood. Authors of a recent systematic review concluded that the evidence so far does not suggest that overweight and obesity in childhood are independent risk factors for risk of increased blood pressure, carotid-intima thickness or cardiovascular disease morbidity or mortality in adulthood. In fact, those who were of lower BMI as children and overweight as adults had the greatest risk of having high blood pressure as adults (Lloyd et al. 2010). Also, findings of the Thousand Families Cohort Study suggested that those thinnest in childhood but overweight in adulthood had the highest overall risk of adult disease (Wright et al. 2001).
In summary, evidence does not suggest that overweight and obesity in childhood are independent risk factors of adult disease. However, it is important not to underestimate the potential problems overweight and obesity may cause in later life because of the potential for tracking into adulthood. Overweight and obesity in adulthood are established risk factors for various diseases, including cardiovascular disease, type 2 diabetes, cancer, aggravation of rheumatic diseases, and asthma and other respiratory diseases.
Prevention and management of childhood obesity
Prevention of obesity is the key to tackling this major public health problem. Treatment of obesity can prove difficult, and therefore health experts believe that much more effort should be put into obesity prevention. A Cochrane review on the prevention of childhood obesity published in 2005 was not able to demonstrate that diet and exercise interventions are effective in preventing weight gain and obesity in children, but found that they can be effective in promoting a healthy diet and increased physical activity levels (Summerbell et al. 2005). However, a systematic review and meta-analysis that considered different settings concluded that nutrition and physical activity interventions in schoolchildren resulted in significant reductions in bodyweight compared with control. The authors found combination intervention, single nutrition intervention and TV reduction intervention to be equally effective. The authors also found that physical activity intervention alone did not result in bodyweight reduction (Katz et al. 2008).
For the prevention of excess weight gain, it is crucial to emphasise the importance of a healthy balanced diet as well as adequate physical activity levels from an early age, with the focus being on general health and wellbeing rather than obesity prevention. Schools have an important role to play here as they provide an environment where consistent healthy eating messages can be applied as part of a whole school approach (see Sections 6 and 7).
In terms of management of established overweight and obesity in children, a recent Cochrane systematic review showed that various forms of intervention seem to be effective (Oude Luttikhuis et al. 2009). The authors identified 64 randomised controlled trials and reported that while there is limited quality data to favour one treatment programme over another, combined behavioural lifestyle interventions can produce a significant and clinically meaningful reduction in overweight in children and adolescents compared with standard care or self-help. They further suggest that in obese adolescents, consideration should be given to the use of either of the drugs Orlistat or Sibutramine, as an adjunct to lifestyle interventions, although this approach needs to be carefully balanced against the potential for adverse effects (Oude Luttikhuis et al. 2009). NICE suggested that a small number of intervention studies found an effect of non-clinical interventions on bodyweight of children and adolescents, although most studies had major limitations (NICE 2006). In its guidance, NICE focuses on prevention rather than management of obesity in non-clinical settings (e.g. schools). For management of obesity, NICE suggests that multicomponent interventions are the treatment of choice. Weight management programmes should include behaviour change strategies to increase physical activity levels or decrease inactivity, improve eating behaviour and diet quality, and reduce energy intake. Interventions should address lifestyle within the family and social settings. NICE recommends BMI as a practical estimate of overweight in children and young people, but use of BMI needs to be interpreted with caution because it is not a direct measure of adiposity. In terms of management of overweight and obesity in children, NICE suggests that the aim of weight management programmes for children and young people may be either weight maintenance or weight loss, depending on their age and stage of growth. NICE also emphasises that if help is offered at school, confidentiality and building self-esteem are particularly important because treating children for overweight or obesity may stigmatise them and put them at risk of bullying, which in turn can aggravate problem eating (NICE 2006a).
4.2 Cardiovascular risk factors
Cardiovascular disease (CVD) is a major cause of adult death and ill health. Autopsy studies have revealed first signs of atherosclerosis to already be prevalent in childhood and it has therefore been suggested that the disease process begins in this age group (Celermajer & Ayer 2006). Autopsy studies have also shown that the extent and severity of arterial fatty streaks or raised plaques is associated with levels of blood lipids, blood pressure, and obesity in childhood and adolescents (Celermajer & Ayer 2006; Steinberger et al. 2009). Obesity is a major influence in the development of cardiovascular risk factors in childhood, including hypertension, dyslipidaemia and diabetes mellitus; and its role is discussed in more detail in Section 4.1.
A strong positive association between total cholesterol and LDL-C and CVD, as well as an inverse relationship between HDL-C and CVD in adults, has been established in a number of major epidemiological studies. As cholesterol concentrations track over time, it is observed that children with unfavourable cholesterol concentrations are more likely to have unfavourable cholesterol concentrations as adults (Celermajer & Ayer 2006). Obese children and those with insulin resistance have an increased risk of dyslipidaemia (Steinberger et al. 2009). Although more evidence is needed to clarify the effect of childhood blood cholesterol concentrations on future CVD risk, public health strategies should aim to maintain cholesterol concentrations at a low level in all children.
Diabetes mellitus is a metabolic disease that is characterised by hyperglycaemia (raised blood glucose) and is associated with accelerated development of vascular disease. Hyperglycaemia is the result of either impaired secretion of insulin (type 1 diabetes), resistance to the effect of insulin in the liver or muscles (type 2 diabetes), or a combination of these pathophysiological situations (Steinberger et al. 2009). Type 1 diabetes is an autoimmune disease where the insulin producing cells are destroyed and insulin needs to be injected. In contrast, type 2 diabetes is mainly found in association with overweight and obesity and treatment generally includes changes in lifestyle, including eating a healthy diet, increasing physical activity and losing weight.
The most frequent type of diabetes mellitus in children and young people is type 1 diabetes, although type 2 diabetes – which is typically a disease of adults – is now being diagnosed in obese adolescents. The prevalence of both forms of diabetes in children and adolescents has increased during recent decades (Aylin et al. 2005; Haines & Kramer 2009; Hsia et al. 2009). A recent estimate of diabetes prevalence in children aged 0-to-17-years is 186 per 100 000 for type 1 diabetes and 3 per 100 000 for type 2 diabetes (Haines & Kramer 2009). Most children with diabetes are aged 10 years or above; 77% of all children with type 1 and 98% with type 2 are in this age group (Haines & Kramer 2009).
Type 2 diabetes is more prevalent in some ethnic groups than others. A recent study showed that the presence of type 2 diabetes precursors in children also differs between ethnic groups living in the UK (Whincup et al. 2010). Compared with White Europeans, South Asian children have higher levels of type 2 diabetes precursors; this is also seen, to a lesser extent, in Black African-Caribbean children (Whincup et al. 2010).
Hypertension is a well-established risk factor for CVD in adults. Evidence shows that children who develop hypertension are more likely to have hypertension as adults and hypertension in childhood is a risk factor associated with early atherosclerotic change (Larson Ode et al. 2009; McCrindle 2010). A well-established risk factor of primary hypertension in children and adolescents is obesity (Celermajer & Ayer 2006; Larson Ode et al. 2009; Steinberger et al. 2009; McCrindle 2010). Studies in the US have shown that there is an association between the prevalence of both pre-hypertension and hypertension in children and incidence of overweight and obesity (see Section 4.1; McCrindle 2010). No data on prevalence of pre-hypertension and hypertension in children is available for the UK.
Management of primary hypertension in children and adolescents should focus on lifestyle changes that help with weight loss, including eating a healthy diet, being more physically active and spending less time being physically inactive. In terms of diet, a recent meta-analysis of ten controlled trials, including almost 966 children, concluded that a modest reduction in salt intake was associated with significant reductions in systolic and diastolic blood pressure (He & MacGregor 2006). See Section 1 for target salt intakes in schoolchildren.
4.3 Iron deficiency anaemia
Anaemia is a global public health problem affecting both developing and developed countries. Globally, the most significant contributor to the onset of anaemia is iron deficiency; it is generally assumed that 50% of all anaemia cases are due to iron deficiency although proportions may vary among population groups and different areas (WHO 2008). The main risk factors for iron deficiency and iron deficiency anaemia are low intake of iron, poor iron absorption (from diets high in phytate or phenolics compounds, or low in ascorbic acid and meat/fish), period of life when iron requirements are especially high (e.g. growth and pregnancy), heavy blood loss as a result of menstruation, and acute and chronic infections (WHO 2008; Falkingham et al. 2010). The presence of other micronutrient deficiencies, including vitamins A and B12, folate, riboflavin and copper can also increase the risk of anaemia (WHO 2008).
It is estimated that around 25% of the world's population has anaemia (around half of which is iron deficiency anaemia). The highest prevalence of anaemia is in pre-school children, with an estimated 47% being affected worldwide (22% in Europe), whereas the worldwide prevalence of anaemia in older children and adolescents is estimated to be approximately 25% (no data for Europe) (WHO 2008).
In UK schoolchildren, iron intakes are particularly critical in girls aged 11-to-18-years, with 46% having iron intakes below the LRNI (see Section 2) (Bates et al. 2010). By comparison, insufficient iron intakes were found in 7% of 11-to-18-year old boys, 1% of 4-to-10-year old boys and 2% of 4-to-10-year-old girls (Bates et al. 2010).
Around 90% of iron in the diet is present as non-haem iron. The remainder exists as haem iron, which is found almost entirely in food of animal origin. Haem iron is generally well absorbed in the intestines. The extent to which non-haem iron is absorbed is principally influenced by systemic iron needs. More iron is absorbed from the diet in a state of iron deficiency and less is absorbed when iron stores are replete. Evidence, mainly from single meal studies, suggests that iron absorption is also influenced by the presence of other components in the diet (e.g. vitamin C and meat enhance absorption, phytates and phenolics compounds inhibit absorption). Evidence from whole diet studies over a number of days or weeks suggests that the overall effect of enhancers and inhibitors on iron absorption is considerably less than predicted from single meal studies (SACN 2010).
In its report on iron, SACN (2010) compared data on concentrations of haemoglobin and serum ferritin (the storage form of iron) from the 2000 NDNS report in children (Gregory et al. 2000) with cut-off values suggested by the WHO (2008). The data show that the prevalence of anaemia in the UK based on WHO cut-off levels in 4-to-6-year-old girls was 9–15% (9% if compared with cut-off levels for the under fives, 15% if compared with cut-off levels for 5-to-12-year-olds). The prevalence of anaemia was lower in older girls and was approximately 2–4.5% in 7-to-14-year-olds; in female adolescents (15-to-18-years) the prevalence of anaemia was estimated to be around 9%. In boys aged 4-to-18-years, the prevalence of anaemia was lower than in girls with around 1–8% having haemoglobin levels below the WHO cut-offs. The prevalence in boys was highest in 11-to-14-year-olds (3–8%), followed by 4-to-6-year-old boys (2.5–8%), and was lowest in 7-to-10-year- (1.4%) and 15-to-18–year-olds (1.1%) (SACN 2010). Anaemia was particularly common in girls who reported that they had tried to lose weight over the past year and among vegetarians (Gregory et al. 2000). Low serum ferritin levels according to WHO cut-offs, indicating iron deficiency, were found in almost 25% of female adolescents aged 15-to-18-years. In younger girls the prevalence was 3–12% and 3–10% in boys. Based on the WHO thresholds for haemoglobin and serum ferritin and data from the NDNS, SACN estimates that around 5% of girls aged 15-to-18-years have iron deficiency anaemia, and lower prevalence rates were indicated for younger girls (1.7–2.5%) and all boys (0.6–1.2%) (SACN 2010).
Anaemia carries implications for both mental and physical performance. Symptoms include fatigue, lassitude and breathlessness on exertion (see Buttriss 2002a). Evidence from observational studies suggests that iron deficiency anaemia is associated with poor cognition in school-aged children. However, iron deficiency anaemia is also associated with a number of socio-economic and biomedical disadvantages that can affect children's development (Falkingham et al. 2010; SACN 2010). Therefore, evidence from observational studies is not adequate to demonstrate a causal effect of iron deficiency anaemia on cognition. A recent systematic review and meta-analysis of studies looking at the effects of oral iron supplementation on cognition concluded that iron supplementation improved attention and concentration in adolescents irrespective of baseline iron status, and improved intelligence quotient in anaemic children. The authors pointed out that the limited number of included studies were generally small, short and methodologically weak (Falkingham et al. 2010). SACN also reviewed the evidence from supplementation trials in children aged 3 years or older and concluded that there is evidence for a beneficial effect of iron treatment on cognitive development in anaemic children. However, SACN pointed out that none of the trials reported long term follow-up of children to determine whether any benefits were sustained (SACN 2010).
4.4 Oral health
The Office for National Statistics carried out its fourth Children's Dental Health Survey in 2003. This survey has been carried out every 10 years since 1973 and aims to establish the state of dental health of children in the UK, and to monitor change since earlier surveys. The surveyed population included children aged 5, 8, 12 and 15 years attending state and independent schools. In addition to dental examinations carried out by trained staff, questionnaires were sent to parents to acquire information on children's oral hygiene and dental care, as well as barriers to dental care (Pendry et al. 2004; Lader et al. 2005).
Data on the prevalence of dental caries in schoolchildren are available from the Children's Dental Health Survey, which was carried out for the first time in 1973. In surveys prior to 2003, dental caries was defined as obvious decay experience, being the sum of teeth with decay into dentine, filled teeth or teeth that were missing due to decay (missing primary teeth were not considered as these are unlikely to have been decayed). The criteria for assessing dental caries were changed for the 2003 survey and, in addition to the above criteria, also included visual caries (decay on surface and visible to the observer, but dentine not obviously cavitated). Where comparison to older data was made, the pre-2003 criteria were applied (Lader et al. 2005).
Primary (‘milk’ teeth)
The proportion of children with dental caries in primary teeth decreased between 1983 and 2003 (Table 18) and, in 2003, there were differences between countries, the highest proportion being observed in Northern Ireland, followed by Wales. Five- and eight-year-old children from Wales and Northern Ireland had higher rates of decay compared with the UK average (Table 19). There are no separate data available for Scotland.
|Year||5 years (%)||8 years (%)|
|Country||5 years (%)||8 years (%)|
There was a clear decrease in dental caries in permanent teeth between 1983 and 2003 in all age groups. The decrease was most pronounced between 1983 and 1993 and more prominent in permanent teeth than in primary teeth (Table 20). The proportion of children with decay in permanent teeth was again highest in Northern Ireland followed by Wales, with the prevalence of decay in 8-, 12- and 15-year-olds from these countries being clearly above the UK average (Table 21).
|Year||8 years (%)||12 years (%)||15 years (%)|
|Country||8 years (%)||12 years (%)||15 years (%)|
The prevalence of tooth decay was higher in schools in deprived areas compared with schools in non-deprived areas for all age groups, and in general more teeth were affected in children from schools in deprived areas.
Tooth surface loss (TSL)
TSL is pathological non-carious loss of tooth tissues resulting from erosion, attrition or abrasion of the tooth enamel. This condition, unlike dental caries, is associated with consumption of acidic foods and drinks. Twenty per cent of 5-year-olds showed TSL on the buccal (outward) surfaces of primary incisors and 53% showed TSL on the lingual (inward) surfaces of the primary incisors. Among 8-year-olds, 4% showed signs of TSL on buccal and 14% on lingual surfaces of permanent incisors, and 10% had TSL on molars. The proportion of children with TSL on the permanent dentition increased with age. Among 12-year-olds, 12% had signs of TSL on buccal and 30% on lingual surfaces of permanent incisors, and 19% on molars. The respective numbers in 15-year-olds were 14% on buccal and 33% on lingual surfaces of permanent incisors, and 22% on molars.
Oral health and hygiene
In 2003, a third of 5-year-olds had some gum inflammation (gingivitis), compared with two-thirds of 8- and 12-year-olds. In 15-year-olds, the proportion with gum inflammation was somewhat lower at 52%. The proportion of children with gum inflammation has increased since 1983 in all age groups, although in 15-year-olds the change was less pronounced than in other age groups. The proportion of children with dental plaque (biofilm formed by colonising bacteria) had also increased since 1983 and was highest in 8- and 12-year-olds (76 and 73%, respectively). Fifty per cent of 5-year-olds and 63% of 15-year-olds had plaque. Levels of calculus (calcified plaque) rose with age from 6% in 5-year-olds to 39% in 15-year-olds, and had increased over the previous 20 years.
Children in Wales were less likely than those in England and Northern Ireland to have plaque, gum inflammation or calculus, although not all differences were statistically significant.
Overall, more than three quarters of children in all age groups in 2003 reported brushing their teeth at least twice a day, which was higher than 20 years ago. Between 19 and 24% of all children reported brushing once daily or less. Girls in all age groups tended to brush more frequently than boys. Generally, more frequent brushing was associated with less plaque and gingivitis, except for 8-year-old children.
Diet and dental caries
Dental caries (dental decay) arises when several factors occur simultaneously, in particular a susceptible tooth surface, presence of acid producing bacteria and a source of fermentable carbohydrate (e.g. sugars and starches). Hence, diet has the potential to influence dental decay. However, the most important strategy is regular (at least twice daily) brushing of teeth with a fluoride-containing toothpaste. Because the introduction of water fluoridation (in some parts of the country) and recognition of the importance of fluoridation of toothpaste (introduced in the mid 1970s), dental caries prevalence has fallen. For example, in 1973, 12-year-olds had an average of five decayed, missing and filled teeth (DMFT), and in 2003, this had fallen to less than one DMFT. Fifteen-year-olds had an average of around eight DMFT in 1973 and 1.5 DMFT in 2003. Fluoride strengthens the tooth enamel, providing resistance to decay (British Nutrition Foundation 1999b).
Sugars and other fermentable carbohydrates are fermented by bacteria on the tooth surface (typically located in dental plaque). This results in localised acid production, which in turn can lead to progressive destruction (demineralisation) of teeth, particularly if pH remains low owing to frequent ingestion of fermentable carbohydrates. Although all fermentable carbohydrates have the potential to cause dental decay, the main dietary factor is frequency of sugars consumption, this being more important than the total amount consumed. It has also been suggested that limiting sugar-containing foods and drinks as well as snack food containing starch (e.g. crisps) to meal times is one way to reduce the incidence of caries, as the saliva produced when chewing restores optimal pH in the mouth. Although sugars and fermentable carbohydrates have been linked to dental decay, EFSA recently concluded that available data do not allow the setting of an upper limit for intake of (added) sugars on the basis of a risk reduction for dental caries. This is because caries development related to consumption of sucrose and other cariogenic carbohydrates does not only depend on the amount of sugar consumed, but it is also influenced by frequency of consumption, oral hygiene, exposure to fluoride, and various other factors (EFSA 2010).
Another factor that affects the risk of developing caries is the retentiveness (stickiness) of the carbohydrate. Foods such as dried fruit or toffees may stick to teeth for a longer time than would occur with less sticky food. Therefore, it is important to brush teeth regularly.
Chewing sugar-free gum, which promotes saliva production, has been found to reduce dental caries. EFSA has accepted a health claim related to Xylitol (artificial sweetener) chewing gum/pastilles and risk reduction of dental decay and has agreed that the wording ‘Xylitol chewing gum reduces the risk of caries in children’ reflects the scientific evidence for caries reduction (EFSA 2008).
Diet and dental erosion
Dental erosion is the loss of hard tissue by chemical etching, without bacterial involvement. Acids responsible for erosion occur in food and drinks, which can either lead to loss of hard tissue or to softening of the enamel or dentine, making it more prone to attrition and abrasion. Softened enamel may be rehardened by saliva, and it is clear that excessive oral hygiene should be avoided after exposure to potentially erosive events. Dietary acids are present, for example, in fresh fruit and fruit juices (e.g. oranges, lemons, limes), and soft drinks (British Nutrition Foundation 1999b).
4.5 Bone development
Optimising bone development during childhood and adolescence is crucial in order to decrease the risk of osteoporosis later in adult life. Optimum bone development is also important for the avoidance of skeletal problems in childhood and adolescence such as rickets, which is a disease where bones are deformed owing to an insufficiency of vitamin D.
Most of the skeletal mass is laid down during childhood and adolescence. It is estimated that by post-puberty (16 years onwards), approximately 80–90% of peak bone mass is achieved (Lanham-New et al. 2007). Throughout early childhood, bone mass increases linearly with skeletal growth, whereas during the pubertal years a rapid increase in bone density can be observed (by as much as 40–70%). Bone density continues to increase for several years after the cessation of growth until peak bone mass is achieved. The exact age at which peak bone mass is attained remains controversial and is generally believed to be between 18 and 35 years of age (Lanham-New et al. 2007).
Beside genetic factors that influence peak bone mass and account for roughly 70–75% of the variance seen (Lanham-New et al. 2007), nutrition and physical activity play an important role in bone development. The main nutrients associated with bone development are calcium and vitamin D. Calcium is the most abundant mineral in the human body. Bones and teeth account for approximately 99% of the body's total content of calcium, where it is a main structural component (stored as hydroxyapatite) (Phillips 2004; Theobald 2005).
Calcium is essential for bone growth as it is required for the mineralisation of bone. An adequate intake of calcium is one of a number of factors that are important for acquiring and attaining optimum peak bone mass. Diets containing insufficient amounts of calcium may lead to a low bone mineral density, which may have implications for bone health, notably risk of osteoporosis, in later life (Theobald 2005). During puberty, the total amount of calcium deposited per day is greater than at any other time in life although, expressed per kg of bodyweight, is less than during infancy and childhood. Therefore, total calcium needs are greater during adolescence than at any other time in life (Theobald 2005) (see Section 1 for DRVs for calcium intake). Data from the latest NDNS report show that 11% of girls aged 11-to-18-years and 6% of boys of this age group have intakes below the LRNI, suggesting insufficient intakes. Only 2% of the girls and none of the boys in the younger age group (4-to-10-years) had intakes below the LRNI (Bates et al. 2010) (see Section 2).
A Cochrane review, looking at the effect of calcium supplementation (including provision in food) on bone density in healthy children, concluded that there was a small effect on total body bone mineral content and upper limb bone mineral density, but no effect at any other site was found. The authors suggest that the increase in bone mineral density was unlikely to result in a clinically significant decrease in fracture risk (Winzenberg et al. 2006). However, the effect of calcium supplementation on bone development remains controversial, with many experts pointing out positive effects of supplementation in various studies (Prentice et al. 2006; Lanham-New et al. 2007). A reason for inconsistencies between studies may be the use of different forms of supplementation, including calcium supplements and food sources of calcium. More studies will be needed to clarify potential effects of supplementation in healthy children. Calcium is present in a wide range of foods in varying amounts and the bio-availability also varies considerably. Dairy products, such as milk, yoghurt and cheese, are plentiful sources of well-absorbed calcium. Fish consumed with soft edible bones (such as whitebait, canned sardines or canned salmon) also contain significant amounts of calcium, as well as foods fortified with calcium (e.g. in the UK white and brown flour are fortified with calcium). Pulses, wholegrains, nuts, seeds, dried fruits and vegetables contain some calcium, although some of these foods also contain substances that bind to calcium and inhibit absorption (e.g. phytates in wholegrains and pulses, oxalate in spinach and rhubarb) (Phillips 2004; Theobald 2005). The contribution of foods to total calcium (and vitamin D) intakes in UK children is shown in Table 22.
|Calcium (average intakes 740–920 mg*)||Milk and milk products (47–48%); cereals and cereal products (27%); vegetables and potatoes (6–7%); meat and meat products (6%); fish and fish dishes (2%); fruits and nuts (1%)|
|Vitamin D (average intakes 2.0–2.2 µg/day*)||Cereals and cereal products (35–37%); fat spreads (21–22%); meat and meat products (20–22%); fish and fish dishes (8–10%); eggs and egg dishes (7%); milk and milk products (2%)|
Vitamin D is critical for bone development and health as it is required for calcium absorption. It is also known to stimulate matrix formation and bone maturation, and enhances osteoclastic activity (osteoclasts are bone-building cells) (Lanham-New et al. 2007). It has been estimated that gut calcium absorption is increased to 30–40% of intake with adequate vitamin D status compared with a 10–15% absorption without adequate vitamin D (Holick 2007). Severe vitamin D deficiency in children results in rickets (Lanham-New et al. 2007). There has been much controversy among experts about which cut-off levels should be used to define optimum vitamin D levels (Lanham-New et al. 2011). Vitamin D is primarily produced in the skin on exposure to sunlight; the amount produced being influenced by latitude, pigmentation of skin and extent of clothing. Some ethnic groups living in the UK are particularly prone to vitamin D deficiency due to the dark pigmentation of their skin coupled with the level of sun irradiation at higher latitudes, as well as cultural clothing norms that limit skin exposure. See Section 1 for more information on sources of vitamin D and Section 2 for information on vitamin D status in UK children and adolescents.
A Cochrane review, summarising the evidence of vitamin D supplementation on bone mineral density in children concluded that although current evidence does not support vitamin D supplementation as a means to improve bone density in healthy children with normal vitamin D levels, supplementation of deficient children may be clinically useful (Winzenberg et al. 2010).
Other dietary factors
Dietary protein intake is also important for bone development and protein-energy malnutrition can lead to skeletal problems. Positive associations between total protein intake, bone mineral content and bone size have been reported in children and adolescents (Prentice et al. 2006). However, there is some controversy about the relationship between dietary protein, in particular that derived from animal sources, and calcium metabolism. In adults, excess dietary protein can result in increased urinary calcium losses and therefore increased bone loss (Prentice et al. 2006; Lanham-New et al. 2007), but little is known about the situation in growing children (Lanham-New et al. 2007).
Vitamin K is also important for the skeleton and deficiency of vitamin K may lead to a reduction in bone formation and decreased bone strength (Lanham-New et al. 2007). In terms of food groups, a high intake of fruit and vegetables has been found to be associated with bone development; the exact mechanisms behind this are yet to be established (Prentice et al. 2006; Lanham-New et al. 2007). High sodium intake and caffeine consumption have both been suggested to negatively influence calcium balance, although the evidence is inconsistent. There has also been concern that carbonated drinks may negatively impact on bone development because of the perception that such drinks contribute to acid load. However, it has been suggested that purported associations between high intakes of carbonated drinks and bone development are due to the displacement of milk from the diet rather than negative effects of carbonated drinks per se (Prentice et al. 2006).
Physical activity is crucial for bone development, particularly high-impact activities that include hopping, jumping and skipping, as well as weight training (Phillips 2004; Hind & Burrows 2007; Lanham-New et al. 2007). For optimal bone development, children and adolescents are advised to follow the UK guidelines for physical activity (see Section 3). However, while weight bearing exercise is known to have a positive effect on bone mineral density, paradoxically bone health is a cause for concern in some girls who are engaged in competitive sports, such as gymnastics or distance running. This may be due to intensive training interfering with growth and development, and efforts to control weight in sports where minimal body fat is perceived desirable. Some highly trained female athletes and ballet dancers have poor bone density as a result of late onset menstruation or amenorrhoea (see Buttriss 2002a).
4.6 Food allergy and intolerance
Food intolerance, which includes food allergy, is an adverse reaction to food that is reproducible and takes place every time contact is made with a particular food or ingredient. If the reaction involves the immune system, it is known as food allergy (Food Standards Agency 2008). Non-allergic adverse reactions to food are mediated by non-immunological mechanisms, including enzyme deficiencies (e.g. lactose intolerance), pharmacological effects and other non-defined idiosyncratic responses (Buttriss 2002b; Food Standards Agency 2008). Most allergic reactions to food are mediated by immunoglobulin (Ig) E and are immediate, an exception being coeliac disease which is an allergic reaction to gluten that is non-IgE mediated (Buttriss 2002b; Mills et al. 2007). Prior to the manifestation of an allergic reaction to a particular food, sensitisation to the food must occur. However, sensitisation to a food does not always lead to clinical reactivity and symptoms of food allergy (Mills et al. 2007). Allergic reactions to food vary considerably in their severity and the discomfort they cause, but the majority are not life-threatening. However, some reactions, known as anaphylactic reactions, can be very severe and even fatal (Buttriss 2002b; Food Standards Agency 2008). The most common cause of this type of reaction is peanuts. The amount of an allergenic food required to provoke a reaction in a sensitive individual varies considerably from person to person and also over time, depending on a range of factors (Food Standards Agency 2008).
Estimates of the prevalence of food allergy in the UK vary but have been suggested to be around 5–8% in children and 1–2% in adults (Food Standards Agency 2008). The prevalence in adults is lower as many children outgrow their allergies, often before they even start school. The incidence of perceived food allergies and intolerances is usually considerably greater than the actual prevalence. For example, in a robust study involving almost 1000 mothers from the Isle of Wight with babies aged 3, 6, 9 and 12 months, between 2.2–5.5% of infants were found to respond to skin prick tests and a subsequent double-blind, placebo-controlled food challenge (only carried out in those with positive skin prick test results) during the first year of life. In contrast, 14.2% of the study population reported that their child suffered from adverse food reactions (Venter et al. 2006). Over-reporting of food allergies and intolerances often leads to an overestimation of the prevalence rates if measurements are based on self-reported data (Madsen 2005; Mills et al. 2007). A meta-analysis of studies has found that the incidence of self-reported food allergies in Europe ranges between 3% and 35%, whereas the incidence rates were lower in studies where subjects were assessed objectively for food-related sensitisation and symptoms (Asero et al. 2006).
Contrary to popular view, the Isle of White Study research team have found that rate of sensitisation to foods has not increased over the last two decades (Food Standards Agency 2008). Although higher hospital admission rates have been reported (Gupta et al. 2007), this may reflect an increase in the awareness of food allergies and in their diagnosis.
Despite the small number affected, food allergies can be life threatening and quality of life can be severely impaired. The majority of food-induced allergies are caused by a small number of foods, namely nuts, peanuts, cows' milk, gluten (wheat, barley, rye), eggs, soya, fish and shellfish, and avoiding the allergen-containing food is the only way to avoid allergic reactions.
Avoidance of food sensitisation in the first place, and therefore the subsequent risk of allergy, would be the best way to prevent allergy-induced illness. For some time, there has been interest in whether early exposure (including in the womb) to particular foods can influence or disrupt the development of normal immune system tolerance. This has resulted in advice on the timing of introduction of foods associated with severe allergy, such as peanuts and gluten. Until recently, pregnant women with a family history of allergic disease were advised as a precautionary measure not to consume peanuts during pregnancy and lactation. However, a recent systematic review (Thompson et al. 2010) has contributed to a change in the recommendations. The UK government now advises that pregnant women who eat peanuts or peanut containing foods are at no greater risk of having a child with a peanut allergy than those who choose to avoid such foods (Food Standards Agency 2009a). The Department of Health currently recommends exclusive breastfeeding for the first 6 months of life and to begin introducing solid foods at 6 months. This recommendation is based in part on the assumption that early exposure to particular foods can result in sensitisation, although some experts challenge this opinion as there is some evidence that there are critical periods in early life when exposure triggers normal immune system tolerance (Du Toit et al. 2008).
An EC-funded project, EuroPrevall, aims to characterise the pattern and prevalence of food allergy across Europe, and investigate the relationship between genetic and environmental factors and the development of food allergy (http://www.europrevall.org). This study, and others in the area, will hopefully shed more light on the development and treatment of food allergies in children.
4.7 Mental health
Depression and anxiety
Depression can affect people at all life-stages and is common in adolescence. Mood shifts in children and adolescents may present as irritability rather than sadness or depression and can interrupt everyday functioning, for example the ability to do schoolwork or enjoy spending time with friends (Bamber et al. 2007).
Most of the evidence around the association between diet and depression comes from studies in adults and tends to focus on specific nutrients. Nutrients that have been associated with depression include n-3 fatty acids and folate. Observational and intervention studies show these nutrients to be low in the diets of people who are depressed, while supplementation leads to improvements in symptoms (Bamber et al. 2007). A study carried out in children aged 6-to-12-years found that n-3 fatty acid supplementation was associated with a decrease in depressive symptoms (Nemets et al. 2006). Other nutrients associated with depression include vitamin B12, vitamin B6, vitamin C, iron, selenium and zinc (Bamber et al. 2007). A link between obesity, unhealthy eating and depression has also been suggested (Bamber et al. 2007; Oddy et al. 2009; Goldfield et al. 2010), although the exact interactions and causation remain unclear. Obesity has been linked to body dissatisfaction, which in turn can lead to shifting of mood and depression. On the other hand, depression may lead to increased energy intake which may lead to obesity. More evidence is needed to explore the relationships between diet, depression and obesity.
Physical inactivity has been linked to depression and anxiety in young people. A Cochrane review looking at the effects of exercise interventions in reducing or preventing anxiety or depression in children and young people concluded that exercise seems to have a small positive effect in reducing depression and anxiety scores. However, the authors point out that the small number of studies and the clinical diversity of participants, interventions and methodology all limit the ability to draw firm conclusions (Larun et al. 2006). Evidence from longitudinal studies suggests that physical activity is associated with a reduced risk of depressive symptoms, anxiety and other emotional problems (Sagatun et al. 2007; Strohle et al. 2007; Wiles et al. 2008; Jerstad et al. 2010). On the other hand, social physique anxiety (the anxiety about other people's judgement of body shape and body image) has been suggested as a barrier to formal exercise, although the evidence is not conclusive (Niven et al. 2009). This could mean that girls who are less confident about their appearance may avoid taking part in exercise, which may aggravate emotional problems.
The illnesses anorexia nervosa, bulimia nervosa, binge eating disorder and their variants are characterised by a serious disturbance in eating, as well as distress or excessive concern about body shape or weight (Thomas 2000). In addition to their impact on psychological well being, they can have a devastating effect on health through the physiological consequences of altered nutritional status and/or purging. The epidemiology of eating disorders has gradually changed. Eating disorders have typically been seen in girls and young women, but there is now an increasing prevalence in males. Of particular concern is the increasing prevalence of eating disorders at progressively younger ages. A US study found that hospitalisations for eating disorders increased by 119% in children younger than 12 years between 1999 and 2006 (Rosen & Committee on Adolescence 2010).
Anorexia nervosa is a serious illness in which people keep their bodyweight abnormally low by dieting, vomiting or exercising excessively, leading to prolonged and extreme weight loss. A major factor in the development of this disease is anxiety about body shape and weight that originates from a fear of being fat or from wanting to be thin (NICE 2004). Factors associated with the onset of anorexia nervosa include perceived pressure from the family and the environment, obsessive desires to be in control of the body, as well as media obsession with thinness and the media's ‘bullying’ of fatness (e.g. celebrities being gibed for gaining weight) (Hill 2006). The effects of anorexia nervosa include loss of muscle and bone strength, cessation of periods and, if prolonged and severe, anorexia can lead to death. Anorexia nervosa in children and young people is similar to that in adults in terms of its psychological characteristics, but children and young people may, in addition to being underweight, also have stunted growth (NICE 2004).
People who suffer from bulimia nervosa feel that they have lost control over their eating, as opposed to obsession with control in anorexic people. Bulimia nervosa is characterised by a cycle of eating large quantities of food (binge eating), and then vomiting, taking laxatives and diuretics (purging), or excessive exercising and fasting, in order to prevent weight gain. In contrast to anorexia nervosa, the bodyweight of people with bulimia nervosa is often normal. Bulimia nervosa can lead to tiredness, feeling bloated, constipation, abdominal pain, irregular periods, or occasional swelling of the hands and feet. Excessive vomiting can cause erosion of teeth, while laxative misuse can seriously affect the heart (NICE 2004)
A large number of people with eating disorders do not meet the strict criteria for anorexia nervosa and bulimia nervosa. These eating disorders are often labelled as ‘eating disorder not otherwise specified’ and their prevalence is estimated to be higher than the prevalence of anorexia and bulimia nervosa. Patients with eating disorders not otherwise specified often experience the same physical and psychological consequences as do those who reach the threshold for diagnosis of anorexia or bulimia nervosa. Athletes and performers, particularly those who participate in sports and activities that reward a lean body (e.g. gymnastics, running, wrestling, dance, modelling) may be at particular risk of developing partial-syndrome eating disorders (Rosen & Committee on Adolescence 2010).
Although the manifestations of these disorders are via the diet, they are in fact psychological disorders and underlying problems need to be treated by trained and expert multidisciplinary teams. The three main categories of contributors include biological and genetic, psychological and socio-cultural factors, which can either occur independently or collectively. Eating disorders appear to run in families. However, whether this is a result of biological/genetic, socio-cultural or psychological factors, or a combination of these, is not clear (see (Hooper & Williams 2011)
There is a widespread belief among experts that nutrition and diet may influence cognitive function. The UK government and those involved in education, as well as parents, are likely to have a particular interest in the association between diet and cognitive function in schoolchildren. A systematic review commissioned by the Food Standards Agency and published in 2008 looked at UK-relevant evidence from controlled trials on the effect of diet on learning and performance of school-aged children (Ells et al. 2008). Another systematic review looked at the effect of breakfast on cognitive function, including studies from populations that are comparable with the UK population as well as studies with non-comparable populations, such as from developing countries (Hoyland et al. 2009).
Breakfast In the review by Ells et al. (2008), the largest number of publications on diet and cognitive behaviour examined the effect of breakfast. Three out of four studies on the effect of breakfast clubs in schools found a small but positive impact on a selection of educational outcomes, while one study found no effect. Four out of six studies looking at breakfast consumption versus fasting identified some improvements in problem solving, attention and episodic memory after cereal consumption and in complex visual display tests after consuming breakfast. Two out of six studies were unable to demonstrate any significant differences. The authors of the review pointed out that it was difficult to draw together findings from the different studies due to numerous inconsistencies between studies and the shortcomings of many studies (Ells et al. 2008).
Hoyland et al. (2009) propose that the majority of studies looking at breakfast versus no breakfast found a positive effect on cognitive function, which they suggest was more obvious later in the mornings. Studies in developing countries found that cognitive performance following breakfast consumption was better in at-risk or under-nourished children, with few if any effects in well-nourished and not-at-risk children. The authors found that data to show that one type of breakfast was substantially better than another was not evident. Studies looking at long-term effects of school breakfast programmes and breakfast clubs were mainly carried out in schools with a high proportion of children from low socio-economic backgrounds or a high proportion of under-nourished and at-risk children. The authors of the review propose that the studies, taken together, showed improvement mainly in mathematics or arithmetic scores, which they suggest may be due to increased attendance or decreased absenteeism. They also suggest that benefits were no greater in or confined to under-nourished or at-risk groups in most studies that also included well-nourished controls. The reviewers pointed out that, overall, the quality of studies was rather poor (Hoyland et al. 2009).
Sugars Six studies included in the systematic review by Ells et al. (2008) considered the effect of sugar intake on learning and behavioural outcomes, five of which were in a population of children with symptoms of attention deficit hyperactivity disorder (ADHD). The authors concluded that short-term exposure to sucrose has no dramatic detrimental effects on educational and behavioural outcomes in school-aged children, when compared with commonly used artificial sweeteners (Ells et al. 2008). A review looking at glycaemic load of breakfast suggested that there was insufficient evidence to demonstrate a consistent directional effect of glycaemic load on short-term cognitive performance (Gilsenan et al. 2009).
Omega 3 fatty acids The systematic review by Ells et al. (2008) included five studies examining the effect of fish oil supplementation on learning and behavioural outcomes. All studies were carried out in a population aged 5-to-13-years with symptoms of neurodevelopmental disorders (dyspraxia and ADHD). Two studies [supplements rich in docosahexaenoic acid (DHA)] found small but statistically significant positive effects on only a few of a number of subjective parental and teacher observations (objective measures not examined). Only one study, using a supplement rich in eicosapentaenoic acid (EPA), reported significant improvements in both objective and subjective behavioural and educational outcomes. The reviewers also discussed findings published following their original systematic search that suggest that fish oil supplements may potentially improve cognitive performance (Ells et al. 2008). However, the findings of two subsequent UK studies do not support this proposition (Kennedy et al. 2009; Kirby et al. 2010). One study, giving EPA and DHA to 8-to-10-year-old children for 16 weeks, found very few significant differences between the supplemented and placebo groups on learning and performance measures (one being in favour of the placebo) (Kirby et al. 2010). A study using DHA for 8 weeks in 10-to-12-year-old children found that the treatment with two different doses (400 mg or 1000 mg) had no consistent or interpretable effect on performance (Kennedy et al. 2009).
Vitamins and minerals There is evidence that deficiency of some nutrients, e.g. iron deficiency anaemia (see Section 4.3), can lead to impaired cognitive function. Vitamins and minerals suggested to be linked to cognitive processes in children are iodine, iron, zinc and vitamin B12 (Black 2003). Low magnesium levels have been reported in children with ADHD (Sinn 2008). In the systematic review by Ells et al. (2008), two studies of low-dose multivitamin/mineral supplementation over several months were included. One reported a moderate, but statistically significant, average increase in the non-verbal IQ of children, although this may have been accounted for by a substantial net IQ increase in just a small sub-sample. A study in UK children found no significant effect of supplementation on verbal and non-verbal IQ. Ells et al. (2008) conclude that these two studies alone provide insufficient evidence to draw conclusions about the effects of low-dose vitamin and mineral supplementation on the IQ score of schoolchildren (Ells et al. 2008).
5 Factors affecting food choice
Socio-economic and regional factors
Socio-economic status has been suggested to impact upon the dietary and lifestyle habits of people within the UK. Data from the Low Income Diet and Nutrition Survey (LIDNS) suggest that this is only true to a certain extent. Although overall reported diets were poor in the low-income population, they were only slightly worse than those of the general population (Nelson et al. 2007; Tedstone 2008). Comparing the findings of LIDNS with data from the 1997 NDNS shows that nutrient intake levels in children and young people are similar in both surveys. However, there were some differences in consumption of certain foods; for example lower intakes of wholemeal bread, semi-skimmed milk, fruits and vegetables, and higher intakes of whole milk, processed meat and non-diet soft drinks were found in the LIDNS (see Section 2) (Gregory et al. 2000; Nelson et al. 2007).
These findings differ from the 1997 NDNS, a stimulus for LIDNS, which found that the energy, protein, total carbohydrate, NMES and NSP intakes of boys whose parents were in receipt of benefits was lower than that of boys whose parents were not. Intakes of some micronutrients, including vitamin C, calcium and magnesium, have also been found to be lower in children from households in receipt of benefits compared with those from households who were not, even when energy intake was taken into consideration (see Section 2) (Gregory et al. 2000).
The area where a child lives was also shown to have an impact on dietary intake in the 1997 NDNS (note Northern Ireland was not included in this survey). For example, boys in Scotland were less likely to have eaten all types of fish (including oily fish) than children elsewhere, and boys and girls in Scotland were also less likely to have consumed many types of vegetables than children in other regions (although it is worth noting there were few regional differences reported for fruit consumption). Chocolate confectionery was also more likely to be consumed in boys in Scotland compared with London and the South East (94% compared with 82%). Boys and girls from Northern England were more likely to have consumed non-diet soft drinks than in other regions (83% of boys and 82% of girls versus 71% of boys and 70% of girls in London and the South East) (Gregory et al. 2000).
Advertising of food to children
The advertising of food to children has undergone considerable change since the previous edition of this Briefing Paper (see Buttriss 2002a). These changes have stemmed from growing concerns about rising levels of overweight and obesity among children, and while it is appreciated that there are likely to be multiple factors that have influenced trends in weight gain, food advertising has been suggested as one factor which may play a role.
In 2004, Ofcom (the independent regulator of television within the UK), commissioned by the government, reviewed the evidence on the effect of food and drink advertising on dietary behaviour in children and concluded that advertising had a modest, direct effect on children's food choices and a larger but unquantifiable indirect effect on children's food preferences, consumption and behaviour (Ofcom 2007). This prompted the Department of Health to propose that there was a ‘strong case for action to restrict further advertising and promotion to children of those foods and drinks that are high in fat, salt and sugar (HFSS)’ (Department of Health 2004b). After an in-depth consultation it was decided that restrictions should apply to televised advertising of food and drink products aimed at children (Ofcom 2007).
Foods that are HFSS are identified using a Nutrient Profiling tool, devised by contractors on behalf of the FSA (Food Standards Agency 2009b). The tool uses a scoring system which identifies the contribution a food makes to nutrients that are beneficial in a child's diet (including protein – used as a proxy for calcium- and iron-rich foods in particular–dietary fibre, fruit and vegetables, and nuts) and compares this (in an algorithm) with the food's contribution to nutrients currently consumed in excess (saturated fatty acids, salt and sugar). The score is calculated on the basis of a 100 g portion of a food (Ofcom 2007; Food Standards Agency 2009b).
The restrictions of HFSS advertising were implemented in a step wise fashion, the final phase coming into force on 1 January 2009, when all HFSS advertising was banned from children's channels (Ofcom 2010). In contrast, products low in fat, salt and sugar, including fruits and vegetables, are not subject to any such advertising rules. Ofcom estimated that, as a result of the regulations, children saw around 37% less HFSS advertising in 2009 compared with 2005. Younger children (4-to-9-year-olds) saw 52% and older children 22% less HFSS advertising (Ofcom 2010). It is not yet known what impact this has had on children's consumption of HFSS foods.
Other social influences
Societal influences can strongly influence diet and physical activity habits, particularly during the impressionable childhood and adolescent years. Popular media is thought to have a large influence on young people's body image (Hogan & Strasburger 2008), and there is often a great deal of pressure placed on obtaining an ‘ideal’ body shape. For young girls, this typically ‘slim’ look is often unobtainable; however, the adoption of unhealthy practices may occur in a bid to try to conform. These practices may include smoking, meal skipping (notably breakfast), as well as severely reducing intake of foods deemed fattening (often red meat and dairy foods, which are sources of protein, iron, zinc and calcium among other nutrients) and the adoption of very low energy (and therefore nutrient) diets. As was shown by a recent survey on the wellbeing of children in England, girls tend to be more dissatisfied with their appearance than boys (Rees et al. 2010); however, data from the 1997 NDNS, which found 16% of girls and 3% of boys aged 15-to-18-years reported being on some form of diet (Gregory et al. 2000), suggests boys also feel such social pressures. Other research has suggested the prevalence of dieting may be a lot higher: French et al. (1995) found 26% of adolescent girls to be restricting fat intake in their study, with extreme dieting methods including fasting and the use of diet pills being among the methods used to lose weight. Of concern is the potential for such behaviours to develop into more serious long term psychological problems (e.g. anorexia – see Section 4.7 for more information) (French et al. 1995).
Adopting a healthy attitude to diet and exercise has become increasingly difficult in a society where obesity is endemic and body fat is stigmatised (Hill 2002; Hill 2006). Children's and adolescents' eating habits are strongly influenced by the world around them, including the attitudes and habits of family, in particular of the mother, and friends (Story et al. 2002). It is therefore important that those involved in children's development and upbringing try to instil in youngsters the need to develop healthy dietary and exercise habits, in the hope that such behaviours will track through into the adult years.
According to a global report, the UK has the highest teenage pregnancy rate in Western Europe (Population Action International 2007). Teenage pregnancy has profound consequences for those affected, and is ‘strongly associated with the most deprived and socially excluded young people’ in society (Department for Culture Schools and Families 2006). Within the UK, the 1999 government's Teenage Pregnancy Strategy outlined plans to help overcome these statistics, by stating how it would accelerate progress already made towards the target of halving the under-18 conception rate by 2010, from a 1998 baseline (Department for Culture Schools and Families 2006). Progress with this strategy is ongoing: the conception rate in 15-to-17-year-olds in England was 44.7 per 1000 women in 1999 and had fallen to 41.2 conceptions per 1000 in 2007; under-16 conception rate in 2007 was 8.3 per 1000. While this is positive news, there is still someway to go if the target is to be achieved. Furthermore, geographical disparities in rates still exist across the country, with girls in the North East being the most likely to become pregnant compared with those elsewhere in England (see (Department for Culture Schools and Families 2009) for further information).
Pregnancy during the teenage years will affect both the emotional and physiological status of the mother. Nutritional demands increase to meet the needs of a growing fetus, at a time when the maternal body still requires extra nutrients for growth and development. This is compounded by the fact that a considerable percentage of young girls have sub-optimal intakes of some nutrients (Gregory et al. 2000). Iron is one such nutrient that is particularly important during pregnancy, but for which intakes are below the LRNI in over half of teenage girls (see Section 2). Epidemiological studies suggest that a low haemoglobin concentration during pregnancy is a marker of increased risk of low birthweight and perinatal mortality, although a causal relationship with iron supply has not been established (SACN 2010). Folate intake is also of particular concern – an adequate intake of folate is essential before and during the first three months of pregnancy, to help reduce the risk of neural tube defects in the developing fetus. It is for this reason that the Department of Health recommends women of child-bearing age to take a 400 µg folic acid supplement daily (Department of Health 2004c). However, as the majority of teenage pregnancies are unplanned, consumption of folic acid supplements prior to conception and during the first trimester of pregnancy is unlikely.
6 Food provision in school
The provision of food in schools has seen major developments over recent years, with new school food standards being introduced in all four areas of the UK. The main aim of these standards is to ensure that children receive a healthy, balanced and nutritionally adequate meal at lunchtime when in school, to provide them with the nutrients needed for healthy growth and development. For decades, school meals have been seen as a means by which to ensure children receive adequate nutrition [see (Passmore & Harris 2004)]. However, evidence began to emerge that the choice of food available was resulting in many children selecting a meal of relatively low nutritional value and therefore school meals were failing to meet children's nutritional needs (Nelson et al. 2004; Nelson et al. 2006). This, coupled with statistics showing that obesity levels were rising in all age groups and patterns of micronutrient deficiencies were common especially in older children (see Sections 2 and 4.1), led the governments of all four UK countries to take action to improve food served within the school environment. With a reported 3.5 million meals being served every day in schools in England and Wales alone (LACA 2004), this action was urgently needed.
Nutritional guidelines for school meals produced in 1992 by the Caroline Walker Trust (The Caroline Walker Trust 1992) have been used as a reference tool for the development of many of the school meal standards in use today. School food standards in place throughout the UK are compulsory and comprise nutrient-based standards as well as food-based standards that are compatible with the government's Eatwell plate (see Fig. 11).
In order to promote a consistent message about healthy eating to children, in most parts of the UK school food guidelines extend beyond school lunches to cover other food served throughout the school day (see Table 23). Nutrient-based standards are compulsory only for school lunches, and compulsory food-based standards cover not only school lunches but also food available from tuck-shops, vending machines, breakfast clubs, mid-morning/afternoon catering, and after school clubs.
|Are school food standards in existence?||Yes||Yes||Yes||Yes – minimum standards. More stringent (but not compulsory) guidelines available in Appetite for Life Action Plan.|
|Do these comprise?||Nutrient based-standards for school lunch?||Yes||No||Yes||No. However, guidelines available (but not compulsory) in the Appetite for Life Action Plan.|
|Food-based standards for food other than school lunch?||Yes||Yes||Yes||No. However, guidelines available (but not compulsory) in the Appetite for Life Action Plan.|
|Are these standards compulsory?||Yes – standards apply to all local authority maintained primary, secondary, special and boarding schools and pupil referral units.||Yes – standards apply to all grant-aided nursery, primary and post-primary schools.||Yes – standards apply to all state funded schools.||Yes – minimum standards apply to all maintained nursery schools, community, foundation and voluntary primary and secondary schools and community and foundation primary and secondary special schools.|
|Free-fruit scheme?||Yes, all 4-to-6-year-olds receive a free piece of fruit or free vegetables daily.||No national programme, however a variety of initiatives exist.||No national scheme currently in existence, instead it is up to local authorities to decide if pupils should receive free fruit.||No national programme exists.|
|For more information about school meal standards see:||http://www.schoolfoodtrust.co.uk||http://www.deni.gov.uk||http://www.scotland.gov.uk||http://www.physicalactivityandnutritionwales.org.uk|
School food standards across the UK
A school meals review panel was set up in 2005 by the Department for Education and Skills to review and develop nutrition related standards for school meals. Its report ‘Turning the Tables: Transforming School Food’ (School Meals Review Panel 2005) called for radical changes to school meals, which included restricting foods high in total and saturated fatty acids, sugar and salt, as well as foods made with poor quality meat. The Panel's recommendations formed the basis of new school standards for all food served within English schools, which were launched in three parts. Firstly, interim food-based standards for school lunches came into force in September 2006, followed by food-based standards for school food other than school lunches in September 2007. Finally, nutrient-based standards for school lunches were developed, which were required by law to be implemented in all primary schools by September 2008, and all secondary schools, special schools and Pupil Referral Units by September 2009. When the nutrient-based standards became law, the interim food-based standards for school lunches were replaced with the final food-based standards, whereas the food-based standards for school food other than lunches remained the same. All standards are legal requirements and apply to all local authority maintained primary, secondary, special and boarding schools and Pupil Referral Units in England (School Food Trust 2008a). The School Food Regulations detail all of these standards (Department for Children Schools and Families 2008).
Food-based standards (see Table 24) apply to all school lunch services, including hot, cold and packed lunch services provided on a school day. The food-based standards for school food other than lunch apply to all food provision (except lunch) up to 6 pm, including breakfast clubs, mid-morning break services, vending machines, tuck-shops, and after school snacks and meals. Independent schools and academies are exempt from the standards but are encouraged to comply.
|Food-based standards for school lunches||Food-based standards for school food other than lunches|
|MORE OF||Fruit and vegetables||Not less than two portions per day per pupil, at least one vegetable and one fruit||Fruit and/or vegetables must be provided at all school food outlets|
|Oily fish||Oily fish must be provided at least once every 3 weeks||No standard|
|Bread||Bread with no added fat or oil must be provided on a daily basis||No standard|
|Drinking water||Free, fresh drinking water should be freely available at all times|
|Healthier drinks||The only drinks permitted are plain water, low-fat milk, fruit juice, vegetable juice, plain soya, rice or oat drinks enriched with calcium, plain fermented milk drinks, combination drinks, flavoured low fat milk; tea, coffee and milk containing less than 5% added sugars or honey|
|RESTRICTED||Meat products||A meat product (manufactured or homemade) from each of the four groups below may be provided no more than once per fortnight across the school day, providing the meat product also meets the standards for minimum meat content and does not contain any prohibited offal: |
Group 1: Burger, hamburger, chopped meat, corned meat;
Group 2: Sausage, sausage meat, link, chipolata, luncheon meat;
Group 3: Individual meat pie, meat pudding, Melton Mowbray pie, game pie, Scottish (or Scotch) pie, pasty or pastie, bridie, sausage roll;
Group 4: Any other shaped or coated meat product
|Starchy food||Starchy food cooked in fat or oil should not be provided more than 3 times a week across the school day|
|Deep-fried food||No more than two deep-fried food items in a single week across the school day|
|Salt and condiments||No salt shall be available to add to food after cooking |
Condiments may only be available in sachets or in individual portions of not more than 10 g or 1 teaspoonful
|Snacks||Snacks such as crisps must not be provided. Nuts, seeds, vegetables and fruit with no added salt, sugar or fat are allowed. Dried fruit may contain up to 0.5% vegetable oil as glazing agent|
|Savoury crackers and breadsticks can only be served with fruit, vegetables or dairy food||Savoury crackers and breadsticks must not be provided|
|Cakes and biscuits||Cakes and biscuits are allowed at lunchtime but must not contain any confectionery||Cakes and biscuits must not provided|
|NONE||Confectionery||Confectionery must not be provided|
The food-based standards can help increase intakes of fruit, vegetables and oily fish, but they may not be sufficiently comprehensive to impact on intakes of fat, salt and sugar. The nutrient-based standards were set in parallel to increase the vitamin and mineral content of school lunches, and to decrease contents of fat, saturated fatty acids, NMES and sodium. Standards for the contribution of macronutrients to energy intake from school lunches (Table 25), and maximum and minimum levels for absolute amounts of macronutrients and micronutrients (Table 26) were put in place. The contributions of macronutrients to energy from school lunches are the same as recommended for total energy intake throughout the day (see Section 1). Maximum levels were set for sodium, NMES, fat and saturated fatty acids, and minimum levels were set for carbohydrate, protein, fibre, vitamin A, vitamin C, folate, calcium, iron and zinc. The standard for energy is based on an average value, rather than a minimum or a maximum value (Table 26). The standards are different for primary and secondary schools, reflecting different nutritional needs at different stages of development (School Food Trust 2008a). The standards are designed to be achieved across the food offered at lunch time rather than meals consumed by individual children.
|Not less than 50% from carbohydrate||Predominantly starch and intrinsic/milk sugars|
|Not more than 11% from non-milk extrinsic sugars|
|Not more than 35% from fat||Predominantly unsaturated fatty acids|
|Not more than 11% from saturated fatty acids|
|Nutrient||Minimum or maximum||Primary||Secondary|
|Energy (kJ)||2215 ± 5% (111)||2700 ± 5% (135)|
|Energy (kcal)||530 ± 5% (26.5)||646 ± 5% (32.3)|
|Saturated fatty acids (g)||Max||6.5||7.9|
|Vitamin A (µg)||Min||175||245|
|Vitamin C (mg)||Min||10.5||14.0|
The School Food Trust carried out a national survey of primary schools in England to assess the impact of the standards on catering provision and pupil food selection and consumption (School Food Trust 2009; Haroun et al. 2010). The researchers found that compared with 2005, caterers now provide a more healthy lunch that meets food-based and most nutrient-based standards, with substantial increases in fruit and vegetable consumption (60% on average) and a 32% decrease in sodium intake. Improvements in relation to the standards still need to be made for some nutrients (e.g. iron and zinc). By limiting the range of foods available to healthier options, pupils now receive and eat healthier lunches. The average meal taken now contains over two portions of fruit and vegetables, and is lower in fat, sugar and salt. Primary school pupils were found to be responding positively to changes that had been made, which suggests that handled correctly, the introduction of healthier food in school is not a barrier to increasing take up in primary schools. Indeed, in both the primary and secondary sectors, take up has increased since the introduction of the final versions of the standards (Nelson et al. 2010). A report on a national survey in secondary schools in England is due to be published on the School Food Trust website in December 2011. For more information on school food provision in England see Nelson (2011) in this issue of the Nutrition Bulletin.
The School Food Trust oversees school food in England; for more information see: http://www.schoolfoodtrust.org.uk.
Scotland led the way in the UK in terms of transforming school food. Hungry for Success (2002), the report of Scotland's Executive Panel on School Meals, set out a whole school approach to school meals, based around the introduction of nutrient-based standards for school meals, to which all state funded schools were recommended to comply. Adoption of these standards was recommended in all special and primary schools in Scotland by 2004 and in all secondary schools by 2006 (Expert Panel on School Meals 2002). The Schools (Health Promotion and Nutrition) (Scotland) Act 2007 (The Scottish Government 2007) builds on the success of Hungry for Success and, together with provision of the Nutritional Requirements for Food and Drink in Schools (Scotland) Regulations 2008 (The Scottish Government 2008b), forms part of a wider health promoting schools approach. The Regulations comprise (1) nutrient standards for school lunches, (2) food and drink standards for school lunches and (3) food and drink standards for school food and drinks other than school lunch, served in breakfast clubs, tuck-shops, vending machines, mid-morning services, community cafes and after school clubs. The Regulations apply to local authority schools, grant-aided schools and hostels for pupils maintained by a local authority. The Regulations came into effect in August 2008 for primary schools and in August 2009 for secondary schools. The nutrient-based standards comprise minimum and maximum levels for the same nutrients included in the English standards: minimum levels were set for protein, carbohydrate, fibre, iron, calcium, vitamin A, vitamin C, folate and zinc; maximum levels were set for total fat, saturated fatty acids, NMES and sodium (The Scottish Government 2008a).
A summary of the food standards for school lunches in Scotland is presented in Table 27, these differ slightly from the English standards. Separate drink standards for schools are included in the Regulations. These, together with food and nutrient standards, can be found in the Healthy Eating in Schools guide from the Scottish government, which aims to support schools in implementing the Regulations (The Scottish Government 2008a). A supplementary guide for children and young people was published in 2010 (The Scottish Government 2010b).
|Fruit and vegetables||A choice of at least two types of vegetables and two types of fruit (not including fruit juice) must be provided every day as part of the school lunch|
|Oily fish||Oily fish must be provided at least once every three weeks|
|Variety of extra bread||Additional bread must be provided every day as a meal accompaniment, with a variety of bread, which must include brown or wholemeal, being provided over the week|
|Oils and spreads||Only oils and spreads high in polyunsaturated and/or monounsaturated fatty acids can be used in food preparation|
|Deep-fried foods||Menus must not contain more than three deep-fried items in a single week |
Chips, if served must be served as part of a meal
|Table salt and other condiments||Additional salt cannot be provided |
Condiments must be dispensed in no more than 10 ml portions
|Confectionery||No confectionery can be provided|
|Savoury snacks||No savoury snacks can be provided except savoury crackers, oatcakes or breadsticks|
Within Wales, the Education (Nutritional Standards for School Lunches) (Wales) Regulations 2001 provide a set of minimum standards with which school lunches must comply (Welsh Assembly Government 2003). They apply to maintained nursery schools, community, foundation and voluntary primary and secondary schools, and community and foundation primary and secondary special schools. As these are minimum standards, local authorities and schools can adopt their own more stringent standards if they choose to do so. However, in a bid to further improve food and drink served throughout the school day, Appetite for Life, produced by the Food in Schools Working Group in 2006 set up by the Welsh government, sets out the strategic direction and actions required to improve the quality of school lunches in Wales (Welsh Assembly Government 2008b). This includes the setting of more stringent food- and nutrient-based standards for school lunches. These standards are applied to all food, not just set menus, provided in school cafeterias and dining rooms at lunchtime. The nutrient-based standards include the same nutrients as in the Scottish and English standards. The food-based guidelines outlined in the Appetite for Life Action Plan are presented in Table 28. Separate standards for drinks provision were also developed; these as well as the nutrient- and food-based guidelines are outlined in the Appetite for Life Action Plan report by the Welsh Assembly Government (2008b).
|Fruit and vegetables||Not less than two portions per day per child, at least one vegetable or salad and one fruit; a variety should be provided over 1 week|
|Oily fish||On the school lunch menu at least once every 2 weeks|
|Deep-fried potato products||Potatoes and potato products cooked in fat/oils in the school kitchen or during manufacture must not be served more than twice a week|
|Deep-fried products||Other food items cooked in fat/oils in the school kitchen or during manufacture must not be served more than twice a week|
|Manufactured meat products||Should not be reformed/reconstituted foods|
|Bread (without spread)||Available throughout lunch, a variety of breads should be encouraged including wholemeal bread|
|Confectionery and savoury snacks||Not to be made available|
|Salt||Not added to vegetables during cooking, restrict or remove salt from recipes and replace with appropriate and acceptable herbs and spices, not available at lunch tables or at the service counter|
Uniquely to Wales, the Welsh Assembly government has made a commitment to provide all children of primary school age in maintained schools in Wales with a free, healthy breakfast, as part of their Primary Schools Free Breakfast Initiative. For more information about this, see (Welsh Assembly Government 2008c).
Nutritional standards for school lunches in Northern Ireland have been produced under the School food: top marks programme, which is a joint venture between the Department of Education, the Department of Health, Social Services and Public Safety, and the Health Promotion Agency for Northern Ireland. Following a pilot in 2004/2005, new nutritional standards for school lunches were introduced and made compulsory from September 2007 (School Food Top Marks 2009a). In April 2008, the nutritional standards were extended to include all other food and drinks provided in school, such as via breakfast clubs, tuck-shops and vending machines (School Food Top Marks 2009b). The nutritional standards are food-based and are similar to those in other UK countries and aim to ensure that more fruit and vegetables are available in schools, and that fresh free drinking water is available. Furthermore, many high fat, high sugar or salted snacks have been replaced with healthier options such as fruit, bread-based snacks, milk and water. Nutrient-based standards for school lunches are not available in Northern Ireland. For more details see School Food Top Marks (2009a) and School Food Top Marks (2009b).
Free school meals
Providing free school meals to children from low-income families is an important public health measure. Children from all areas of the UK are eligible for free school lunches if their parents receive various forms of assistance, including Income Support, Income-related Jobseekers Allowance and support under Part VI of the Immigration and Asylum Act 1999 (for full information see http://www.Direct.gov.uk). It is estimated that about 1.8 million children and young people are entitled to free school meals; however, approximately one in five children fail to take up this provision in primary schools and about a quarter in secondary schools (LACA 2004). One commonly cited reason for this is the perceived stigma associated with receiving free school meals, which prevents parents signing up for free meals, as well as eligible children taking up their entitlement (Harper & Wood 2009).
Uptake of school meals in primary schools in England during 2008/2009 was around 40%, with the vast majority of the remainder bringing a packed lunch (School Food Trust 2009). In contrast to lunch and other food provided by schools, for which clear guidelines exist, there are no official guidelines for packed lunches brought to school from home. While some primary schools have introduced packed lunch policies to support healthier eating and offer clear guidance and an opportunity to improve food consumed by all pupils, there is little evidence of their effectiveness (School Food Trust 2009), and school lunches generally remain the healthier option (Pearce et al. 2011). The School Food Trust and the British Nutrition Foundation provide tips for healthy school lunch boxes on their websites (http://www.schoolfoodtrust.org.uk/schools/projects/packed-lunches and http://www.nutrition.org.uk/healthyliving/healthyeating/healthy-packed-lunches).
The Primary School Food Survey 2009 found that healthier food and drink items were chosen and eaten more frequently by pupils taking a school lunch compared with those bringing a packed lunch, and packed lunches often included items now restricted in school lunches (School Food Trust 2009) . Two thirds of pupils taking school lunches took servings of vegetables and salad compared with only 8% of pupils bringing packed lunches. Similar trends were seen for water. Far fewer pupils taking school lunches ate confectionery, non-permitted drinks and snacks. Average nutrient intakes from school lunches as eaten were more often in line with healthy eating recommendations than intakes from packed lunches. The nutrient content of an average packed lunch contained more carbohydrate, NMES, fat, saturated fatty acids, vitamin C, sodium, calcium, and less protein, fibre and zinc compared with the average school lunch (School Food Trust 2009; Pearce et al. 2011).
A recent meta-analysis of studies comparing school lunches with packed lunches found that differences in nutrient provision were larger for all nutrients after the introduction of food-based standards compared with the period of no standards, with school lunches providing a more favourable nutrient composition than packed lunches (Evans et al. 2010a). Evans and colleagues also carried out a randomised intervention trial named ‘SMART’ to improve the food and nutrient content of children's packed lunches. The researchers provided the intervention group members with a SMART lunch box (two plastic food boxes and a lunch box cooler bag) and supporting materials, including wall charts with ideas for packed lunches, a few weeks of menus, reward stickers and information leaflets on how to encourage children. The control group only received a simple one-page leaflet on how to improve children's packed lunches. The results showed that, in the intervention group, moderately higher weights of fruit, vegetables, dairy and starchy foods and lower weights of savoury snacks were provided to children. Children in the intervention group were also provided with slightly higher levels of vitamin A and folate. Levels of fats, sugars and sodium did not improve, and despite an emphasis on starchy foods and drinking water, the weight of sandwiches and sweetened drinks did not change (Evans et al. 2010b).
Schemes encouraging fruit and vegetable consumption
Despite the fact that there are clear public health messages throughout the UK encouraging the consumption of fruits and vegetables, research consistently shows that children do not eat enough, with the latest NDNS survey (using disaggregated data) reporting 11-to-18-year-olds eat on average less than half the 5 A DAY recommendation (no data yet available for younger children) (Bates et al. 2010). Providing free fruit to schoolchildren is seen as a way to tackle health inequalities and to help ensure all children get a healthy start in life. However, the provision of free fruit in schools is highly variable across the UK and mainly restricted to younger age groups.
Within England, four- to six-year-old children who attend a Local Education Authority maintained infant, primary or special school are eligible to receive a free piece of fruit or free vegetables each school day. While participation in the School Fruit and Vegetable Scheme (SFVS) is voluntary, schools are encouraged to participate. The roll out of the SFVS was complete in England by late 2004. It was initially funded by National Lottery money and is now funded by the Department of Health (Department of Health 2010). The most recent evaluation of the scheme found that children receiving the SFVS ate more fruit and vegetables in 2008 compared with 2004 when the scheme was initiated, although changes may partly be explained by the introduction of school food standards. It was suggested that effects of the intervention do not carry over into the home environment (Teeman et al. 2010).
While Wales does not have a national fruit and vegetable scheme in schools, the Fruit Tuck Shop initiative is one which encourages pupils, parents and staff to set up fruit tuck-shops in schools to provide fresh fruit, dried fruit or fruit juice to schoolchildren throughout the school day (Physical Activity and Nutrition Network Wales 2009). A study evaluating the impact of the Fruit Tuck Shop initiative in schools in deprived areas found that, in isolation, fruit tuck-shops were not effective in changing children's snacking behaviour in schools, but that fruit tuck-shops had a greater impact when reinforced by school policies restricting the types of foods students were allowed to bring to school (Moore & Tapper 2008).
Schools in Northern Ireland can select from a variety of initiatives that focus on healthy snacking during break time. Examples include the Boost Better Breaks award and the Smart Snack award, both of which state that for schools to gain membership they must only offer milk (and/or water) and fresh fruit and vegetables at break times. Information about these and other schemes in Northern Ireland can be found in the Learning to Eat Well Report (Health Promotion Agency for Northern Ireland 2001).
Within Scotland a free fruit scheme was in existence across all publicly funded schools between 2003 and 2006, and formed part of the Scottish Executive's Health Improvement Programme. As part of this scheme, all children in primaries 1 and 2 (ages 4-to-7-years) received free fruit 3 times per week. This scheme has now ended but The Schools (Health Promotion and Nutrition) (Scotland) Act 2007 gives local authorities the power to decide whether they choose to provide free fruit during the school day (The Scottish Government 2007). An evaluation of the original scheme, published in 2005, found that authority professionals and school staff members perceived that the initiative had been very successful. For example, 90% of school respondents thought that the initiative had brought about an improvement in general eating habits and almost 60% perceived that pupils were consuming more fruit and vegetables as part of their school meals (MacGregor & Sheehy 2005).
There has been a trend over recent years for schools to introduce breakfast clubs, particularly in primary schools. This has been driven by concerns that a substantial proportion of pupils are not eating breakfast and arrive at school hungry, which may impact negatively on school performance (see Section 4.7). In addition to the provision of food, breakfast clubs can also help develop social skills and provide opportunity for additional learning through ‘play’ activities, or provide time to complete homework.
The School Food Trust carried out a study looking at the potential benefits of breakfast clubs, comparing 13 primary schools with breakfast clubs to 9 schools without, all located in deprived areas of London. One year after introduction, average Key Stage 2 results were statistically significantly higher by 0.72 points in the schools with breakfast clubs compared with a non-significant 0.27 point increase in the schools without breakfast clubs. This difference was sustained over the next few years with no further increases. Schools believed that they had reaped significant benefit through the introduction of breakfast clubs, especially in the case of the most socially deprived. The benefits included improvement of social skills, of punctuality of children who were frequently late and of children's health and concentration levels (School Food Trust 2008b). A recent review on breakfast clubs concluded that there are benefits to mental performance and social development, although it is unclear whether such benefits are derived from the consumption of breakfast per se, the environment or a combination of the two. The authors also suggest that benefits of breakfast clubs are more pronounced in deprived areas (Defeyter et al. 2010).
Nutritional guidelines for breakfast clubs as well as other resources that support schools in setting up breakfast clubs are provided by ContinYou, a UK community learning organisation (http://www.continyou.org.uk).
7 Food in the curriculum
The UK comprises four countries, each of which has its own independent curriculum.
Reviews of the primary and secondary curricula, ready for teaching from September 2014, are underway. While the review process takes place, schools should follow the current curriculum in place (http://curriculum.qca.org.uk/). In primary schools (5-to-11-years) food is taught as a compulsory part of the curriculum – mainly through the subjects of Design and Technology (D&T); Science; and Personal, Social and Health Education (PSHE). Each of these three subject areas specifically highlights aspects of food education for children. Combined, they provide opportunities for children to learn how to cook, understand and apply healthy eating messages and learn about the underpinning scientific principles of food science and food safety.
In secondary schools, food is taught mainly through D&T: food. Within this subject, pupils learn about healthy eating, ingredients, equipment and cooking. Nutrition and digestion are also taught in Science, and theoretical aspects of healthy eating and general health are built into PSHE. The curriculum for this age range was updated in 2007. Food education aspects were emphasised in D&T, with specific references being made to cooking, healthy eating, food safety and nutritional needs. To support this change, schools were able to offer the Licence to Cook programme as a non-statutory entitlement. The contract for this project has now ended. The British Nutrition Foundation was part of a consortium contracted by government to develop the resources for this initiative. The project website, developed by the British Nutrition Foundation, had over 650 000 registered student users. Food education, through the D&T curriculum, is optional.
The primary curriculum in Northern Ireland is set out in six areas of learning, with aspects of food being taught through different areas in a multi-disciplinary fashion. Food education is supported in primary schools (ages 5-to-11-years) through the subjects of The World Around Us (Science and Technology, Geography) and Personal Development and Mutual Understanding. In Northern Ireland references to specific understanding or practical cooking activities are not generally highlighted. However, guidance documents are available to help teachers plan appropriate activities for the children they teach.
At secondary school, food is taught through three main areas of learning: Learning for Life at Work (Home Economics); Science and Technology (Science); and Learning for Life and Work (Personal Development). Home economics is compulsory for all secondary school-aged pupils (ages 11-to-14-years), and is taught through 3 themes: Healthy Eating, Home and Family Life, and Independent Living. The concept is to help all young people learn practical skills in food safety and preparation, as well as the opportunity to explore real issues that they may face as family members, citizens and consumers. It is hoped that this approach will help support them for future independent living. The primary and secondary curricula are available at http://www.nicurriculum.org.uk.
The curriculum in Scotland (http://www.ltscotland.org.uk/curriculumforexcellence) has been through a comprehensive review, with Curriculum for Excellence being published in 2009. The curriculum, for children aged from 3-to-18-years, shows the progression for different aspects of food education, known as lines of development. Food aspects are most explicitly highlighted for teaching through three of the curriculum areas: Health and Wellbeing; Science; and Technologies. However, with a strong emphasis on inter-disciplinary (cross-curricular) learning, links can be made (and are actively encouraged) with other curriculum areas.
The curriculum clearly highlights food education learning, for both primary and secondary schools – all of which is statutory. For example, Health and Wellbeing includes the study of energy and energy balance (Physical Activity and Health), as well as nutrition, safe and hygienic practices, and food and the consumer (Food and Health). In Science there are links to body systems and cells, and to the properties and uses of substances. Lastly, Technologies provides the food contexts for developing technological skills and understanding.
The curriculum in Wales (http://www.learning.wales.gov.uk), which was updated in 2008, ensures that children in primary and secondary schools experience learning about food. The three areas of the curriculum where food is mainly featured are: D&T: food; Science; and Personal and Social Education. The area where most children learn about food, particularly undertaking and linking practical cooking work to elements of nutrition, is D&T: food. This is a compulsory component of the curriculum, for children aged 7-to-14-years, covering aspects of cooking skills, food safety and hygiene, and application of healthy eating, as well as considering issues surrounding sustainability and the science behind food.
Supporting the curriculum
The British Nutrition Foundation runs an education programme for UK schools, entitled Food – a fact of life (FFL), which provides a range of free resources. In 2010 the FFL website (http://www.foodafactoflife.org.uk), where most of the resources are available, received over one million visits. FFL provides teachers with a comprehensive collection of resources to support the education of children and young people aged 3-to-16-years. Broadly it provides information in the following topic areas: healthy eating; diet and health; cooking; food safety; and farming. FFL supports the curricula throughout the UK and has been developed to provide a progressive framework to support and inspire all those involved in food and nutrition education. In addition, continuing professional development for teachers is also offered.
Except for a small range of printed posters about nutrients and cooking, the resources are available in a range of digital formats. These include worksheets, videos, podcasts, excel templates, differentiated online tutorials, recipes, interactive whiteboard activities, PowerPoint presentations and information pages. A series of eSeminars is also provided for students and teachers.
8 Promoting healthy lifestyles in children
In recognition of the growing problems of obesity and physical inactivity among today's children, many initiatives have been developed, both at national and local level, to try to halt and even reverse these trends. It is recognised that the solutions to such problems are far from simple. The initiatives discussed below all outline ways to support children and their families to lead healthier lives.
Examples of governmental initiatives across the UK
Healthy Weight Healthy Lives
Healthy Weight Healthy Lives was a cross-governmental strategy for England by the previous government that aimed to support people to maintain a healthy weight and encourage physical activity, thereby creating a healthy society (HM Government 2008). Published in January 2008, the document set out a strategy to make England ‘the first nation to reverse the rising tide of overweight and obesity’. The initial focus of the campaign was on children, with the aim of reducing the proportion of overweight and obese children in 2020 to 2000 levels. In order to do this, the programme laid out immediate plans to, among other things, invest in an evidence-based social marketing campaign (Change4Life); ensure all schools are Healthy Schools; and develop tailored programmes to increase participation in physical education.
Change4Life and SmallSteps4Life
Change4Life is a society-wide movement that has continued under the Coalition government and that encourages people to ‘eat better, move more, and live longer’. The campaign began in 2009, with the aim of making weight and physical activity ‘hot-topics’. Launched in a number of phases, it began by addressing the issue of obesity, before going on to personalising it to individuals and families, and then inspiring and supporting people to change their behaviour. The campaign, initially targeted at families with young children, looked at topics including ‘me size meals’ and ‘snack swaps’. Smallsteps4life is a school focused approach addressing healthy eating, exercise and emotional health of schoolchildren. It provides material for teachers, and includes challenges for students and pledges from students. For more information see http://www.nhs.uk/Change4life and smallsteps4life.direct.gov.uk.
The Department for Health and the Department for Children, Schools and Families (DCSF) set up the Healthy Schools initiative in England as a key delivery mechanism to help achieve targets outlined in Healthy Weight Healthy Lives (HM Government 2008) and The Children's Plan from the DCSF [see (Department for Children Schools and Families 2007)]. The Programme was based around four themes, relating to both the curriculum and the school environment: (1) Personal, Social, Health and Economic education; (2) Healthy Eating; (3) Physical Activity; and (4) Emotional Health and Wellbeing. The previous government set a target for all schools to be participating in the Healthy School Programme, with 75% to have achieved Healthy School status, by the end of 2009.
In July 2010, the new Coalition government confirmed that Healthy Schools will continue, recognising that the initiative plays an important role in helping children and young people reach their full potential. However, the programme organisation is changing to reflect new health policies and priorities. The Healthy Schools website was archived in April 2011 and a new Healthy Schools toolkit went live on the Department for Education website. The toolkit is based around a health and wellbeing change model. It is designed to enable schools to ‘plan, do and review’ health and wellbeing improvements for their children and young people. For more information about Healthy Schools visit http://www.education.gov.uk.
Food and Fitness– Promoting Healthy Eating and Physical Activity for children and young people in Wales
This five-year implementation plan, launched in 2006, aimed to build upon the many national strategies already in existence in Wales (including Climbing Higher – the Welsh Assembly Government Strategy for Sport and Physical Activity, and Food and Well Being: Reducing Inequalities Through a Nutrition Strategy for Wales), as well as local programmes, and provide a framework for integrating action on nutrition and physical activity for children and young people in Wales (Welsh Assembly Government 2006). The plan was based around seven key actions, which look at nutrition and physical activity both within and outside the school environment, in a bid to provide a co-ordinated approach to food and fitness to improve the health of the Nation's children. One such action focused on extending the Welsh Network of Healthy Schools scheme, which is similar to the Healthy Schools scheme in operation in England.
Healthy Eating, Active Living– An action plan to improve diet, increase physical activity and tackle obesity
This action plan from the Scottish Parliament states how the country aims to improve the diet and physical activity habits of the nation set over the period of 2008–2011, in a bid to establish a base from which to tackle the Nation's obesity problems (The Scottish Government 2008c). In this action plan the Scottish government sets out commitments aimed at improving the health of Scottish people. The commitments are targeted at various population groups, including children, and address various issues, including diet and physical activity.
Preventing overweight and obesity in Scotland: a route map towards healthy weight
This Route Map, developed by the Scottish Government and the Convention of Scottish Local Authorities (COSLA), outlines a plan to ‘reduce the rate of increase in the proportion of children with their Body Mass Index outwith a healthy range by 2018’ (The Scottish Government 2010a). The policy directions set out in this document are aimed at central and local government decision-makers working with their partners in agencies, the third sector, NHS Scotland and business to develop and subsequently deliver the long-term solutions to this problem. The preventative actions outlined in this report are grouped under four categories: (1) Energy consumption – controlling exposure to, demand for and consumption of excessive quantities of high calorific foods and drinks; (2) Energy expenditure – increasing opportunities for and uptake of walking, cycling and other physical activity in our daily lives and minimising sedentary behaviour; (3) Early years – establishing life-long habits and skills for positive health behaviour through early life interventions; and (4) Working lives – increasing responsibility of organisations for the health and wellbeing of their employees. A joint governmental leadership group, including Ministers, COSLA leaders and key stakeholders including the NHS and the public health community is scheduled to be the visible focus of the Route Map and to ensure its implementation by holding decision-makers to account.
Investing for Health
Investing for Health is the public health strategy for Northern Ireland (Department of Health Social Services and Public Safety 2002). Published in 2002, this action plan focuses primarily on reducing health inequalities within the population, and therefore focuses on lower income groups rather than setting targets for the population as a whole. It does, however, include children from low-SES backgrounds. By setting out aims to improve the dietary habits of this group, it hopes to reduce commonly seen problems of this population subset, including dental decay.
A Children's Environment and Health Strategy for Europe
The Children's Environment and Health Action Plan for Europe (CEHAPE) is an initiative led by the WHO Regional Office for Europe. Launched in June 2004, it was signed by all 53 member states of the WHO European Region, including the UK. Within the UK the Health Protection Agency became responsible for evaluating children's environmental health, and recommending how the UK can protect the health of children and young people from environmental hazards (Health Protection Agency 2009). Priorities outlined in this include reducing the prevalence of overweight and obesity, and reducing morbidity from a lack of adequate exercise, by implementing health promotion activities that focus on diet, physical activity and health, and providing safe, secure and supportive environments for children to be active within. The UK strategy builds on and complements policies and activities already undertaken by government departments, devolved administrations, local and regional authorities and the NHS.
Examples of other schemes in existence within the UK
Mind, Exercise, Nutrition. . . . Do It! (MEND) is a social enterprise, whose aim was to ‘enable a significant, measurable and sustainable reduction in global childhood and family overweight and obesity levels’. MEND claims to be the first clinically proven community based child weight management programme. MEND 5–7 and MEND 7–13 are offered to those children aged 5-to-13-years considered to be above a healthy weight, and their families, and are free to attend. These MEND programmes consist of two-hour sessions run twice a week over a 10-week period, in which parents and children are taught about food and nutrition and what encompasses a balanced diet; are encouraged to become more active; and are also taught techniques to help keep them motivated and ensure the new lifestyle changes taught are adhered to. MEND 2–4 focuses on encouraging children aged 2-to-4-years and their parents to adopt healthy habits early on, and can be attended by children of any weight. A randomised controlled study evaluating the effectiveness of the MEND programme on obese children aged 8-to-12-years found that participation in the programme was effective in reducing adiposity in children and effects were sustained 9 months after the intensive part of the intervention. The authors also pointed out that the programme was one of the few paediatric obesity interventions which conforms to expert recommendations (Sacher et al. 2010). For more information on the MEND programmes, see http://www.mendprogramme.org.
Let's Get Cooking
Let's Get Cooking is a national network of cooking clubs for children, families and their communities across England. The programme started in 2007 and during its first five years, Let's Get Cooking is using £20 million from the Big Lottery Fund to set up the first 5000 clubs. Let's Get Cooking has three key targets: (1) by the end of the 5-year programme more than one million children, family members and members of the local community will increase their food preparation or cooking skills as a result of Let's Get Cooking; (2) 70% of participants who learn a new healthy eating skill through Let's Get Cooking will replicate that skill at home; and (3) 50% of children, young people and families who participate in Let's Get Cooking will increase their intake of nutritionally healthy food. Let's Get Cooking has already exceeded these targets with more than a year still to run. Cooking clubs that join Let's Get Cooking receive funding for cooking equipment and club-running costs, training for adult helpers and a range of resources. Let's Get Cooking resources include a start-up pack for each club, wall charts, food safety advice, child-friendly versions of recipes, a termly activity and newsletter. All clubs have their own club page on the website and have access to downloadable resources and advice. The aim is that Let's Get Cooking clubs will be sustainable and that they continue to run after funding has ended. For further information visit http://www.letsgetcooking.org.uk.
Food Dudes is a healthy eating school-based intervention targeted at primary schoolchildren. This programme (undertaken in the school environment) uses influential role models (food dudes) to encourage children to repeatedly taste fruits and vegetables. During the 16-day intervention children are shown six short Food Dudes video episodes and letters of encouragement are read to them. Home packs are also provided to ensure healthy behaviours learnt in the classroom are continued in the home environment. After this initial phase, children continue to be encouraged to eat fruit and vegetables with the use of tools such as classroom wall charts to record consumption. The children are presented with fruit and vegetables during break time and lunch. In 2007, the Irish government made the Food Dudes programme available to all primary schools in the country. The programme has also been rolled-out in selected areas of England (∼130 schools), with a view to eventually making it nation-wide.
Studies in the UK and Ireland have shown that the Food Dudes programme significantly increased consumption and liking of fruits and vegetables in children, both during (Lowe et al. 2004; Horne et al. 2009) and after the programme (Lowe et al. 2007; Horne et al. 2009). In the Irish study, the effect of intervention was compared with a school where fruit and vegetables were presented but no intervention was conducted. Both in the short and long term, fruit and vegetable consumption was increased only in the intervention group. One year after the programme, the fruit and vegetable content of lunch boxes packed by parents was significantly increased in the intervention group, which suggests an overall positive influence of the programme on fruit and vegetable intake in children, even outside the school setting (Horne et al. 2009). For more information visit http://www.fooddudes.co.uk.
Walk to school initiative
The aim of this campaign, which started in 1996, was to encourage parents, children and young people to make walking to school part of their daily routine. The campaign is run by the national charity Living Streets. As part of the campaign, two national awareness events are run each year: Walk to School Week in May and Walk to School Month in October. A year-round walking promotion scheme called Walk Once a Week is aimed at primary schools and Campaign-in-a-box and Free your Feet are aimed at secondary schoolchildren. For more information visit http://www.walktoschool.org.uk.
The Foundation wishes to thank the members of the Foundation's Scientific Advisory and Industrial Scientists Committees who have kindly commented on the contents of this Briefing Paper. We are also grateful to Kellogg's for financial assistance to support some of the time spent writing this paper, and to Heather Yüregir who contributed to an early draft whilst working at the Foundation.
Conflict of interest
The Foundation is grateful to Kellogg's for financially supporting some of the time spent on the preparation of this Briefing Paper. However, the views expressed in this paper are those of the authors alone and Kellogg's have not been involved in writing or shaping its contents.
Since drafting the paper, data for the second year of the NDNS Rolling Programme was published (combined with year 1). The data for the second year confirm the findings of year one.