Effect of micronutrient supplementation on linear growth of children.

This review summarizes the results of published, randomized clinical trials that have examined the impact of administration of micronutrients, singly or in combination to infants, preschool and school children on linear growth. Supplementation of single micronutrients resulted in small or no benefits on linear growth. A meta-analysis of zinc supplementation trials confirmed that zinc has a significant but small impact (0.22 sd units) on length gain in children 0-13 years of age. However, a recent study reported a substantially greater benefit (>1 sd) in stunted and non-stunted breast-fed infants 6-12 months of age. With iron supplementation, a beneficial effect was found only in anemic children. Vitamin A supplementation trials have reported little or no benefit on linear growth. Data currently available suggest some impact in children with clinical or biochemical vitamin A deficiency, but this issue needs confirmation. Few studies could be identified where a combination of micronutrients was given as a supplement or as fortified food; in the latter set of studies energy availability was assured. The impact on length without multiple micronutrient supplementation was no greater than that observed with single micronutrients. In conclusion, zinc and iron seem to have a modest effect on linear growth in deficient populations. Vitamin A is unlikely to have an important effect on linear growth. Limited available evidence does not allow us to conclude whether a combination of micronutrients, with or without additional food, would have a greater impact than that seen with zinc alone.