Separate and joint effects of micronutrient deficiencies on linear growth

Recent studies have investigated the effect of micronutrient deficiencies on growth stunting, with special attention toward the effect of zinc, iron, vitamin A and iodine deficiencies. In Mexico, the prevalence of growth stunting in children <5 y old is approximately 24%; it is higher in rural areas and lower in urban areas. In an initial study, the effect of zinc and/or iron supplementation on linear growth was investigated in a longitudinal, placebo-controlled design. After 12 mo of supplementation, there was no difference between the groups supplemented with zinc, iron or zinc plus iron and the placebo group. At baseline, 82% of the children in this study were deficient in at least two out of the five micronutrients that were determined, and 73% were anemic. In another study, a mixture of those micronutrients that were documented to be lacking in Mexican children was formulated in a supplement and given to Mexican children over a period of 12 mo in a longitudinal, placebo-controlled, supplementation design. Children in the low and medium socioeconomic status grew about 1 cm more than similar children in the placebo group. This difference was not found in children of high socioeconomic status. It is suggested that, in most cases, growth stunting is associated with marginal deficiencies of several micronutrients and that in populations with multiple micronutrient deficiencies, the effect on linear growth of supplementation with single nutrients will not be significant. Supplementation with multiple micronutrients is expected to be more effective, but even in that case the actual increment in height was less than the expected potential increment.