Micronutrients and Childhood Growth: Current Evidence & Progress

Vitamins and minerals are essential for growth and metabolism. The World Health Organization (WHO) estimates that more than 2 billion people are deficient in key vitamins and minerals. Groups most vulnerable to these micronutrient deficiencies are pregnant and lactating women and young children; given their increased demands. Although direct causal information on the link of micronutrient deficiencies to maternal and fetal malnutrition and child growth are difficult indirect information related to risks and intervention studies do suggest a close relationship between key micronutrients in mothers and children with impaired growth. These include iron, zinc and multiple micronutrients. Micronutrient deficiency is prevalent in both underweight and obese populations and is linked to pregnancy outcomes. Iron supplementation can protect against low birth weight (RR 0.83, 95% CI 0.73-0.94 - malaria endemic areas); however, approximately 40% of women worldwide still have anaemia during the preconception period. Strategies, including iron fortification of food and co-administering supplements with other interventions, such as intermittent deworming, can improve the iron status of women of child-bearing age but have not been consistently shown to reduce IUGR.

Recent evidence also suggests a possible benefit in at-risk populations in replacing iron-folate supplementation with multiple micronutrient supplementation in pregnancy, further reducing the risk of small for gestational age birth (RR 0.91, 95% CI 0.84-0.97). Calcium and zinc deficiencies have been linked to adverse birth outcomes and maternal complications and supplementation during pregnancy has been found to improve maternal and newborn health outcomes. Similarly while postnatal micronutrient supplementation and fortification studies in childhood have not shown consistent effects on growth (other than zinc on height [SMD 0.09, 95% CI 0.06-0.13], zinc deficiency [RR 0.49, 95% CI 0.45-0.53]), recent data on multiple micronutrient supplementation via micronutrient powders (reduced risk of iron deficiency anemia: RR 0.43, 95% CI 0.35-0.52 and reduced stunting with modified MNPs in one study in term low-birth-weight infants OR 0.35, 95% CI 0.15-0.84) and small-quantity lipid supplements also appear promising.

In summary, while several strategies are in use globally to address micronutrient deficiencies in children with a focus on survival, but relatively few have addressed growth, and none at scale. These have included targeted supplementation as well as food fortification strategies. This presentation will suggest a few plausible strategies at key periods of risk and opportunity, and discuss next steps in relation to the sustainable development goals.