Description of the condition
Vitamin and mineral deficiencies are highly prevalent among children of preschool and school age (usually 24 to 59 months of age and 5 to 12 years of age, respectively), limiting their health and daily performance. In addition to anaemia, frequently reported micronutrient deficiencies in these age groups are those of iron, vitamin A, zinc and iodine.
Anaemia is a condition characterised by a reduction in the body's oxygen-carrying capacity. It is estimated that over 1.6 billion people, or a quarter of the world's population, are anaemic. The prevalence of anaemia is highest (47.4%) among preschool-age children and over 25% of school-age children. Most anaemia occurs in low- and middle-income countries, particularly in Asia, Africa and South America (WHO/CDC 2008).
Causes of anaemia include, iron, folate, vitamin B12 and vitamin A deficiencies, chronic inflammation, parasitic infestations and inherited blood disorders (WHO 2001; Jimenez 2010). Around half of this burden worldwide is assumed to be due to iron deficiency in malaria-endemic areas and more than half (about 60%) in malaria-free areas (Rastogi 2002; Stoltzfus 2004; WHO 2009a). Iron deficiency can be caused by chronic poor dietary iron intake (in quantity and quality), together with increased iron requirements resulting from growth and from losses due to intestinal parasitic infestations and menstruation in postmenarchal girls (WHO 2001). Anaemia in children is diagnosed when the haemoglobin (Hb) concentration in the blood is below a predefined cut-off value, which varies with age and the residential elevation (WHO 2011a). Iron deficiency anaemia is diagnosed by the combined presence of anaemia and iron deficiency, measured by ferritin or any other biomarker of iron status such as serum transferrin receptors or zinc protoporphyrin (WHO 2011b).
Iron deficiency anaemia in children of preschool and school age is associated with considerable morbidity. This condition appears to be associated with potentially irreversible impairment of cognitive development in preschool-age children and with reduced learning and educational performance in school-age children (Lozoff 2007). Iron deficiency has been estimated to contribute to 0.2% of deaths in children under five years, and every year approximately 2.2 million years are lost due to iron-induced disability worldwide (measured in disability adjusted life years (DALYs), a measure of overall disease burden, expressed as the number of years lost due to ill-health, disability or early death) (Stoltzfus 2004; Black 2008; WHO 2009a).
On the other hand, vitamin A deficiency, the leading cause of childhood blindness and an important contributor to young child mortality (WHO 2009a), affects an estimated 190 million preschool-age children, mostly from the World Health Organization (WHO) regions of Africa and South-East Asia (WHO 2009b). Zinc deficiency may impair physical growth, increase susceptibility to infection and affect neurobehavioural development (Brown 2009). Some authors have estimated that zinc deficiency is responsible for about 4% of child mortality (Black 2008) and that supplementing children with this nutrient may help reduce deaths related to diarrhoea and pneumonia (Yakoob 2011). Iodine deficiency affects more than one-third of school-age children worldwide and results in developmental delays and other health problems (Andersson 2005). Vitamin D deficiency and folate insufficiency may also be a concern during childhood. Vitamin D has a key role in bone metabolism (Winzenberg 2011) while adequate folate and folic acid intake is particularly important for pubescent girls who are capable of reproduction, as poor maternal folate status around the time of conception increases the risk of neural tube and other defects at birth (Mulinare 1988). Unfortunately, to date there are insufficient data to estimate the global magnitude of inadequate folate or vitamin D status among any populations, including children.
In low-income countries, some nutritional risk factors increase the incidence or severity of infectious diseases and contribute to a high number of deaths and loss of healthy years. Micronutrient deficiencies (iron, vitamin A and zinc) in combination with childhood underweight and suboptimal breastfeeding cause 7% of deaths and 10% of total disease burden (WHO 2009a). In 2010, globally, an estimated 27% (171 million) of children younger than five years were stunted and 16% (104 million) were underweight. Africa and Asia have more severe burdens of undernutrition, but the problem persists in some Latin American countries (Lutter 2011). Underweight and undernutrition particularly increase child death and disability. Due to overlapping effects, these risk factors are responsible for an estimated 3.9 million deaths (35% of total deaths) and 33% of total DALYs in children less than five years old. Their combined contribution to specific causes of death is highest for diarrhoeal diseases (73%) and close to 50% for pneumonia, measles and severe neonatal infections (WHO 2009a).
Description of the intervention
Public health strategies to address micronutrient malnutrition include prevention of parasitic infestations and other infections, dietary diversification to improve the consumption of foods with highly absorbable vitamins and minerals, fortification of staple foods, provision of supplementary foods and provision of supplements in the form of pills and tablets (Bhutta 2008), with the latter being a widespread intervention.
Currently the World Health Organization (WHO) recommends a supplemental provision of 2 mg of elemental iron per kilogram body weight per day for three months in children less than six years of age born at term. Children of school age and older should receive 30 mg of iron and 250 μg (0.25 mg) of folic acid daily, particularly in populations where anaemia prevalence is greater than 40% (WHO 2001). The intermittent use of iron supplements has also recently been recommended as a public health strategy for these age groups in settings where anaemia prevalence is higher than 20% (WHO 2011c). Both supplementation regimens have proven to be effective in reducing the risk of having anaemia and iron deficiency (Gera 2007; De-Regil 2011a). Though the current recommendations only include iron alone or with folic acid, it has been suggested that administration of additional micronutrients may prevent or reverse anaemia derived from other nutritional deficiencies (Bhutta 2008) and also have positive effects on length or height and weight, serum zinc, serum retinol and motor development (Allen 2009). However, the long regimen duration and side effects associated with daily iron supplementation (for example, gastrointestinal discomfort, constipation and teeth staining with drops or syrups) and the still reduced implementation of large-scale intermittent supplementation have limited the use of vitamin and mineral supplements and led to the development of new approaches to provide iron and other nutrients.
Point-of-use fortification of foods with micronutrient powders has been proposed as an alternative to oral supplements and central fortified foods to provide micronutrients to different age groups ((Zlotkin 2001; Zlotkin 2005). It refers to the addition of vitamins and minerals in powder form to energy-containing foods at home or in any other place where meals are to be consumed, such as schools, nurseries and refugee camps. Micronutrient powders can be added to foods either during or after cooking or immediately before consumption without the explicit purpose of improving the flavour or colour. In some cases point-of-use fortification is also known as home fortification.
Point-of-use fortification with micronutrient powders could be described as a hybrid intervention between mass fortification of staple foods or condiments and targeted vitamin and mineral supplementation. The uniqueness of this intervention results from the mixture of advantages and disadvantages inherited from both parent interventions. Point-of-use fortification is similar to mass fortification because the vitamins and minerals are added to foods or condiments regularly consumed and usually does not require additional changes to dietary intake behaviours. Point-of-use fortification entails the fortification of foods immediately before consumption at home or at another point of use such as schools or child care facilities and there is no long-term interaction between micronutrients and food that can diminish their shelf life. In mass fortification, conversely, micronutrients are added to staple foods or condiments during industrial processing and are more prone to the potential undesirable chemical interactions over time which affect the food sensory properties as well as the bioavailability of some micronutrients.
Like micronutrient supplementation, point-of-use fortification with micronutrient powders is targeted to specific populations so that the number and amount of micronutrients can be tailored to meet the target groups' needs without increasing the risk of overload among other population groups. Also typical of vitamin and mineral supplementation, point-of-use fortification allows for flexibility in the provision regimen (for example, daily, intermittently) (Hyder 2007), and can be adapted according to the selected delivery channel (for example, health or school systems or social protection programmes) or context.
Both micronutrient supplementation and point-of-use fortification of foods with micronutrient powders require an active participation from the target population in order to achieve high coverage and regular and appropriate use. However, in comparison to supplementation, the addition of micronutrient powders to the food or meal may result in a higher acceptance among children and caregivers as a result of the lower number of side effects (Zlotkin 2005) and tastelessness of the product when prepared correctly. It is still unclear whether the absorption of micronutrient powders mimics that of supplements or that of mass fortification.
Point-of-use fortification of foods with micronutrient powders containing at least iron, vitamin A and zinc is recommended to improve iron status and reduce anaemia among infants and children aged 6 to 23 months of age (WHO 2011d).
How the intervention might work
Micronutrient powders were initially conceived as a way to deliver a novel iron compound, encapsulated ferrous fumarate, which is an iron salt covered by a thin lipid layer aimed at preventing the interaction of iron with foods. The encapsulation minimises changes caused by iron to the taste or colour in the added food (Liyanage 2002). However, other iron compounds have also been tested. Micronised ferric pyrophosphate has produced a similar haematological response in 6 to 23-month old children in comparison to encapsulated ferrous fumarate but it is still too expensive to be extensively used in community interventions (Christofides 2006; Hirve 2007). More recently sodium iron EDTA has been proposed as a more efficacious fortificant that, given in a low dose, could produce similar effects on haemoglobin as those observed with ferrous sulphate among school-age children, particularly when added to cereal-based foods that are rich in inhibitors of iron absorption (Troesch 2010). Independently of the source, the iron is frequently accompanied with other micronutrients such as zinc, vitamin A, vitamin C, vitamin D or folic acid, and in some cases micronutrient powder formulations may include up to 15 vitamins and minerals. These formulations are currently developed by various manufacturers (De Pee 2008; de Pee 2009). From the packaging perspective, micronutrient powders were initially delivered in single-dose sachets, which are lightweight, simple to store and transport, and allow easier dosage control (De Pee 2008; SGHI 2008), although the disposal of non-degradable sachets has raised some environmental concerns. Currently the package of the micronutrient powders has been broadened to the use of bulk packs from which powders are added over the meals by using measuring spoons.
The use of micronutrient powders by children aged 6 to 23 months has been reported to reduce the risk of having anaemia and iron deficiency in settings where anaemia prevalence is higher than 20%; an effect apparently similar to that achieved by oral iron and folic acid supplements (Dewey 2009; De-Regil 2011b). Although most of the trials have examined the provision of micronutrient powders on a daily basis, other studies suggest that providing this intervention in a flexible or intermittent regimen, and hence a lower overall monthly dose, produces the same haematological response as daily use of micronutrient powders (Sharieff 2006; Hyder 2007; Ip 2009). The intermittent provision of iron was proposed more than 25 years ago as a feasible public health strategy to supplement children's and women's diets and to reduce anaemia, as it is supposed to maximise absorption by provision of iron in synchrony with the turnover of the mucosal cells (Berger 1997; Viteri 1997; Beaton 1999).
An important consideration when providing supplemental iron to children is the presence of malaria (Okabe 2011). Approximately 40% of the world population is exposed to the parasite and it is endemic in over 100 countries (WHO 2009a; WHO 2010a). In 2008, malaria accounted for 8% of deaths of children under five globally and for 27% of deaths of children under five in Africa (WHO 2010b). Of all the complications associated with malaria, severe anaemia is the most common and causes the highest number of malaria-related deaths. Although the mechanisms by which additional iron can benefit the parasite are far from clear (Prentice 2007), it has been hypothesised that the provision of iron along with foods or low doses of iron, either as encapsulated ferrous fumarate or sodium iron EDTA, might help to prevent anaemia at the time of infection if it reduces the amount of free iron (non-transferrin-bound iron) available to the parasite (Hurrell 2010).
In addition to malaria, another safety concern related to the use of micronutrient powders is their possible effect on diarrhoea. Some trials have reported an increase in the number of episodes after initiating the intervention, followed by a decrease in the frequency of liquid stools after few days (De-Regil 2011b). As a preventive measure, some organisations have advocated the widespread distribution of information on the prompt detection and treatment of diarrhoea (WFP/DSM 2010). Despite these possible caveats, the use of micronutrient powders has been considered by some as one of the most cost-effective strategies to prevent vitamin and mineral malnutrition (Horton 2010).
Why it is important to do this review
The use of micronutrient powders for home or point-of-use fortification of complementary foods among infants and young children aged 6 to 23 months of age has been shown to be effective in reducing anaemia and iron deficiency in young children. The initial success of this intervention has encouraged its use in other vulnerable populations such as children of preschool and school age, as the distribution of micronutrient powders can potentially build on existing school feeding programmes. Currently this intervention has been pilot-tested in over 40 countries for various population groups (often children 6 to 59 months of age (UNICEF/CDC 2010)), but its large-scale use is as yet limited. To date, there is no systematic assessment of the effects of micronutrient powders provision among preschool and school-aged children to inform policy-making.
This review will complement the findings of other systematic reviews that explore the effects of home fortification with multiple micronutrient powders in children less than two years of age (De-Regil 2011b) and among pregnant women (Suchdev 2011).