Iron and zinc deficiency in children in developing countries

Abstract

Fortification is beneficial, but the best strategy for delivery is unclear

In this week's BMJ Sazawal and colleagues report a trial of milk fortified with multiple micronutrients (as a strategy to deliver zinc and iron) in children in India.¹ They found a significant reduction in severe illness and the incidence of acute respiratory infections and diarrhoea. Although data on the impact of the intervention on iron and zinc status are not presented, the functional benefits are consistent with the previously recognised benefits of zinc supplementation on the burden and severity of diarrhoeal diseases and respiratory infections.²

Iron deficiency ranked ninth among 26 risk factors included in the global burden of disease study, and accounted for 841 000 deaths and 35 057 000 disability adjusted life years lost.³ Large sections of populations in Africa and Asia are at risk of dietary zinc deficiency and resulting high rates of stunting.⁴ Correcting micronutrient deficiencies can help reduce child mortality,⁵ but it is unclear how these deficiencies can be dealt with at the population level. Although combinations of iron and zinc have been suggested as appropriate strategies for rectifying deficiencies of multiple micronutrients in children at risk, the benefits may not be additive because of potential interactions.⁶

Despite promotion of micronutrient supplements,⁷ evidence from many supplementation trials in children is mixed. Some trials using dispersible tablets containing multiple micronutrients have found no significant benefits on functional outcomes.⁸ One study in children in Peru with persistent diarrhoea found higher rates of diarrhoea, respiratory infections, and febrile episodes in the children who received multiple micronutrients and zinc compared with those given zinc supplementation alone.⁹ However, in Karachi daily micronutrient and zinc supplementation reduced rates of diarrhoea.¹⁰ The findings from a recent large scale trial of iron and zinc supplementation in a malaria endemic area in Zanzibar are more worrying.¹¹ In this trial, which compared daily iron and folic acid with iron and folic acid and additional zinc or placebo in infants, the iron and folic acid supplementation arms were stopped early because of a significantly higher rate of mortality (12% higher risk, 95% confidence interval 2% to 23%, P=0.02) and hospital admission (11% higher risk, 1% to 23%, P=0.03).

These data have raised concerns about the safety of large scale iron supplementation programmes in malaria endemic areas, and highlighted the need for alternative strategies to deal with deficiencies in iron and other micronutrients in children at risk. These include fortification of commonly consumed foods, condiments, and staples such as wheat flour. These may be useful for adults, but because of the limited consumption of some of these foods by young infants and children, they may not be the most effective means of delivering recommended amounts of micronutrients.

An alternative strategy might be to fortify commonly consumed centrally processed complementary or weaning foods. However, the availability and cost of such foods in developing countries precludes their widespread use. Alternative strategies include the addition of microencapsulated forms of iron and other micronutrients in the form of “sprinkles” (sachets of fortified powder) to commonly used foods available at home.¹² Although sprinkles are generally added to foods, much effort may be needed to induce behaviour change and to monitor changes. Fortification of commonly used food items for children, such as milk, offers an attractive alternative. Sazawal and colleagues'¹ finding of the acceptability of fortified milk as a delivery vehicle are supported by similar findings from Mexico.¹³ In the Mexican study milk fortified with ferrous gluconate and zinc oxide reduced anaemia and iron deficiency.

Notwithstanding the benefits, milk fortification is expensive, and central processing and commodity costs are high. The usefulness, cost effectiveness, and sustainability of this approach must be evaluated at scale in representative populations. A few examples are available of efforts to improve complementary feeding practices as a way of increasing micronutrient intake. The remarkable benefits on growth seen in Peru after a nutrition and health education intervention delivered by the health system suggest that this may be feasible in communities where food availability and choice are not a problem.¹⁴ However, this approach may not work in places like India, where poverty and religious beliefs preclude adequate intake of micronutrient containing foods such as meat and poultry products. If the availability of food can be ensured through appropriate financial support and social insurance schemes, these interventions are the most logical way to provide iron and zinc to young children.

Availability of fortified milk poses a risk to programmes for the support of exclusive breastfeeding in such countries, so their use and promotion must be strictly targeted and monitored. There is therefore a pressing need to evaluate such interventions in large scale community studies before they can be recommended.