Fish plays a useful role in a healthy and balanced diet, and its consumption has long been associated with several health benefits. Fish provides a variety of nutrients, including protein and long-chain omega-3 polyunsaturated fatty acids (n-3 PUFAs), as well as micronutrients including selenium, iodine, potassium, vitamin D and B-vitamins. Intakes of some of these micronutrients, including iodine and vitamin D, are low in some population groups in the UK, which makes fish a valuable contributor to intakes of these. The long-chain n-3 PUFA eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), present in oil-rich fish and fish oil, have been suggested to be associated with beneficial health outcomes. In this paper, we review the evidence associating fish and long-chain n-3 PUFAs with various health outcomes.
Evidence from observational studies shows a protective effect of fish intake on risk of cardiovascular disease (CVD; including stroke). Eating at least two portions of fish per week has been associated with a 23–25% lower risk of death from coronary heart disease (CHD) compared with those eating no or very little fish; eating fish once a week has been associated with a 15% lower risk of CHD death. Fish intake seems only moderately associated with lower risk of stroke, with results from meta-analyses showing a risk reduction of between 6% and 18% in those eating fish 2–4 times per week compared with those eating none. There have been some inconsistencies in study findings relating to fish intake and risk of CVD. Differences in habitual fish intakes of the study populations may account for some of this inconsistency. Evidence from randomised controlled trials (RCTs) on the effect of long-chain n-3 PUFA supplementation on CVD risk has come mainly from secondary prevention studies and is inconsistent. While early studies support a protective effect, recent studies do not support the hypothesis that long-chain n-3 PUFA supplementation is beneficial in secondary prevention of CVD. Different study outcomes have been influenced by variations in study design and the characteristics of the study populations. Furthermore, the increased use of modern treatments for cardiovascular risk factors (e.g. statins) may not have been sufficiently controlled for in more recent studies. Treatment doses of long-chain n-3 PUFA also varied substantially between studies, ranging from 0.3 to 6.9 g/day.
Current evidence suggests that there is no association between fish consumption and risk of type 2 diabetes. We also found no evidence to suggest that fish intake has a protective effect on several types of cancer (pancreas, prostate, bladder, stomach and ovaries). However, studies do suggest that maternal fish intake during pregnancy may reduce the risk of eczema and asthma in her baby, the evidence being somewhat more consistent for eczema. There may also be a link between fish intake during infancy and childhood and the risk of developing asthma and eczema later in childhood, although the evidence is inconsistent and more studies are needed to clarify the situation.
The long-chain fatty acid DHA is crucial for development of the brain and the central nervous system in early life. While studies suggest that fish intake in early life contributes to cognitive development, supplementation with EPA and DHA does not seem to have a beneficial effect on cognitive function in childhood. The European Food Safety Authority (EFSA) suggests that pregnant and breastfeeding women increase their intake of preformed DHA by 100–200 g/day in addition to the suggested average intake level of long-chain n-3 PUFA for adults (250 mg EPA + DHA combined). EFSA proposes that an intake of 1–2 portions of oil-rich fish per week should be compatible with an adequate DHA supply during pregnancy and lactation. There is some evidence to suggest that higher fish intake, dietary DHA intake and DHA levels in the blood among older adults may be positively associated with a lower risk of dementia and Alzheimer's disease (AD). In some prospective studies, risk of AD and dementia in those having the highest fish intake, or the highest blood DHA levels, was about half that of those who ate a little or no fish or had a low blood DHA level. In one prospective study, eating fish once a week was associated with a 60% lower risk of AD compared with those who rarely or never ate fish. However, some studies have found no association, and more evidence will be needed to draw reliable conclusions. Fish intake may be associated with slower cognitive decline, but the evidence is very limited and more studies are needed. Data from RCTs do not suggest that long-chain n-3 PUFA supplements are effective in preventing cognitive decline. There is some evidence from cohort and cross-sectional studies that fish intake may be associated with better bone health, but not all studies have found such an association. Oil-rich fish, in particular, is an important dietary source of vitamin D, which is important for bone health, and fish consumed with soft bones are a good source of calcium, which is the most abundant mineral in the skeleton.
When making recommendations on fish intake, consideration has to be given to the sustainability of fish supplies. Much work has been done already to ensure that fish stocks are not depleted and more efforts will be required to ensure supplies of fish for future generations.
Overall, it is evident that including fish in the diet is associated with several health benefits. The extent to which long-chain n-3 PUFA per se contributes to these various effects has yet to be established. It is likely that other components in fish, such as selenium, potassium, vitamin D or B-vitamins, and other dietary aspects (i.e. foods typically eaten with fish or foods displaced by fish) contribute to the positive health effects.
In recent years, there has been controversy about the healthiness of red meat, prompting suggestions that people should limit their consumption. However, national dietary surveys indicate that UK diets can be low in nutrients typically found in red meat, e.g. vitamin B2, vitamin D, iron, magnesium, zinc, selenium and potassium, particularly among low-income groups, teenagers and females. This article examines the nutritional challenges from infanthood to old age and considers whether there is still a role for red meat in helping people to achieve their dietary requirements. The fossil record indicates that early man evolved as an omnivore, with meat representing a significant source of protein and nutrients in the prehistoric diet. Modern diets offer substantially more variation in protein sources yet the range of nutrients supplied by red meat and their high bioavailability may make meat particularly suitable for human diets. Studies suggest that low intakes of red meat are a marker for iron insufficiency, while inclusion of red meat in the diet is associated with higher mineral intakes. Moderate amounts of lean red meat provide a wide range of important nutrients, without substantially increasing intakes of energy and saturated fatty acids. While concerns have been raised about the potential impact of red meat on the risk of chronic disease, the data are mostly observational and may be confounded by cooking methods or other dietary factors. In conclusion, integrating red meat into diets across the age spectrum, from infanthood to old age, may help to narrow the present gap between micronutrient intakes and recommendations.
Supplements of vitamins and trace elements are consumed widely in the UK, yet there is little evidence that their ingestion is beneficial to health or wellbeing. This review summarises the evidence for health benefits or harm in the situations where supplements are taken.
In only a few cases does the Department of Health recommend supplements in the otherwise healthy population – folic acid before and in the early stages of pregnancy, as requirements are higher, and vitamin D in infants under 5 for example, as their diet is inadequate and they are unlikely to get enough from exposure to sunlight.
Deficiency of individual micronutrients leading to signs of clinical deficiency is fairly common in clinical practice (e.g. anaemia due to iron deficiency, or folate or vitamin B12 deficiency) and it is clear that the relevant nutrient must be provided to correct the deficiency state. Subclinical deficiency is more common, where the deficit in a nutrient is not sufficiently severe to cause clinical signs, but there may be metabolic or non-specific clinical effects. Benefits of supplements on immune function or cognition in these situations have been difficult to prove. In particular, concern about the adequacy of the antioxidant defences has led to several studies of high-dose antioxidants in an attempt to reduce mortality from cardiovascular disease or cancer. These have been found to lead to an increase, rather than a decrease, in mortality.
There is good evidence that benefit is obtained from ingestion of micronutrients as part of a varied, balanced diet, including at least five portions of fruits and vegetables per day. Purified supplements may be of value in certain at-risk groups who are known to have a poor or inadequate diet. In such cases, supplements should be limited to provision of no more than the Reference Nutrient Intake to minimise the risk of excess.
Neural tube defects (NTDs) annually affect an estimated 320 000 newborns worldwide. Folic acid (FA), provided through supplementation and fortification, is an effective primary-prevention strategy for NTDs if consumed in the periconceptional period. However, the potential impact of FA supplementation is tempered by low compliance. Countries that mandate FA fortification of wheat flour report an average reduction of 46% in NTD birth prevalence and favourable benefit : cost ratios of 12–48:1. Despite the well-documented benefits of fortification and the new evidence that provides a better understanding of purported risks associated with FA, European countries have yet to embrace this public health initiative. Viable primary-prevention strategies are needed given that an estimated 4500 NTDs occur in the 27 countries of the European Union annually, of which 72% end in terminations. Many existing factors will facilitate the success of FA flour fortification programs in the region: widespread consumption of wheat-based products, a technologically advanced milling industry, experience adhering to and monitoring food safety measures, and familiarity with mandatory food fortification.
Food-based dietary guidelines are often developed at country level to assist in bringing dietary intakes closer to nutrient intake goals and, ultimately, to prevent nutrition-related diseases. However, high food prices, alongside growing inflation, increasingly restrict food choices. This can leave those who are already vulnerable and less well off more exposed to the associated health implications of a nutrient deficient diet. With food and nutrition security being a high priority on the global nutrition agenda, this paper explores the feasibility of food-based dietary guidelines to assist in improving food and nutrition security, focusing on nutritionally vulnerable groups in South Africa. It is argued that increased food prices, together with population growth, urbanisation and inflation, constrain everyday healthy food choices of a large proportion of South Africans. The South African food-based dietary guidelines released in 2012 advocate the consumption of a daily diet containing a variety of foods. Unfortunately, even when the most basic and low-cost food items are selected to make up a recommended daily diet, the associated costs are well out of reach of poor individuals residing in South Africa. The average household income of the poor in South Africa equips many households to procure mainly low-cost staple foods such as maize meal porridge, with limited added variety. Although the ability to procure enough food to maintain satiety of all family members might categorise them as being food secure, the nutritional limitations of such monotonous diets may have severe implications in terms of their health, development and quality of life. Food-based dietary guidelines alone have little relevance in such circumstances where financial means limit food choice. Alternative interventions are therefore required to equip the poor to follow recommended healthy diets and to improve individual food intake and nutrition security.
Water is essential for health and vital for all bodily functions. If water losses are not replaced then dehydration can occur and even mild dehydration is associated with negative effects on health including impaired cognitive function. Studies in schoolchildren have found that many are arriving at school with a hydration deficit and, once they arrive, they are not drinking enough fluid throughout the day to maintain adequate hydration levels, thus potentially affecting their performance at school. Therefore, there is a need to highlight the importance of adequate hydration among schoolchildren. However, there is often confusion among parents, carers, health professionals and teachers about how much fluid children need to drink, as well as what drinks are most appropriate. This article provides a summary of the development of the Healthy hydration guide for children that was produced to help parents, carers, health professionals and teachers, and indeed children themselves, to choose a healthy balance of drinks to ensure optimal performance and health. It is hoped this resource will help children aged 4–13 years to establish healthy drinking behaviours.
It is firmly established that humans need to obtain sufficient vitamin D in order to optimise calcium absorption and thus ensure robust skeletal health throughout the life stages. Vitamin D research is rapidly expanding, with significant interest in the potential health benefits to conditions such as diabetes, multiple sclerosis, tuberculosis and dementia. Yet, as the field has expanded, gaps in knowledge have emerged. One of the most pertinent questions at present is whether the two forms of vitamin D (vitamin D2 and D3) are equal in their physiological effect. Emerging evidence challenges this long-held assumption and raises the possibility that there may in fact be a distinct and significant difference between the efficacy of vitamins D2 and D3 that could have substantial impact in terms of vitamin D status.
We know that improving maternal and infant nutrition prior to conception and up to 2 years is the most fundamental and impactful way to positively affect the long-term health of the population in both the developing and developed world. Evidence demonstrates that suboptimal maternal nutrition impairs fetal growth and development and can lead to cognitive impairment and an increased risk of non-communicable disease in adult life. Improving maternal diet and nutritional status will be a significant and cost-effective step in tackling both malnutrition and chronic disease globally. However, this long-term goal cannot be achieved without general recognition and meaningful commitment on both a national and international level to implement long-term strategies to support all women of childbearing age to make healthy diet and lifestyle choices before, during and after pregnancy.
The Foresight report has described an unprecedented confluence of pressures whereby a growing, and in some cases, increasingly prosperous global population, alongside increasing demand for limited resources and the pressing need to address environmental challenges, including climate change and changing weather patterns, means that food security is seriously and increasingly threatened. Much of the discussion has focussed on greenhouse gas emissions associated with food production and the contribution from meat production and dairying has been highlighted. These protein-rich foods are features of Western-style diets and as such make a substantial contribution to intakes of a wide range of essential nutrients. Therefore, it is important to understand the impact on overall dietary patterns and associated nutrient intakes if consumption levels fall, as well as the impact from a sustainability standpoint. From a nutritional perspective, the initial knee jerk reaction around simply eating less meat is already being replaced by a more sophisticated debate that is now considering whether a healthy diet, as currently framed by food-based dietary guidelines, can also be a sustainable dietary pattern now and in the future. There are some important questions that need to be addressed in order for a clearer picture to emerge. For example, it is as yet unclear what dietary choices consumers would make if their consumption of these foods were to be reduced, what effect these choices would have on their health and on sustainability of the food supply, and which groups of the population or individuals within households will be most vulnerable, recognising that there are demographic changes already underway associated with an ageing population. This paper provides a viewpoint through the lens of nutrition and summarises some of the initiatives already underway in relation to food security.