Separate and joint effects of micronutrient deficiencies on linear growth

Recent studies have investigated the effect of micronutrient deficiencies o n growth stunting, with special attention toward the effect of zinc, iron, vitamin A and iodine deficiencies. In Mexico, the prevalence of growth stun ting in children <5 y old is similar to 24%; it is higher in rural areas an d lower in urban areas. In an initial study, the effect of zinc and/or iron supplementation on linear growth was investigated in a longitudinal, place bo-controlled design. After 12 mo of supplementation, there was no differen ce between the groups supplemented with zinc, iron or zinc plus iron and th e placebo group. At baseline, 82% of the children in this study were defici ent in at least two out of the five micronutrients that were determined, an d 73% were anemic. In another study, a mixture of those micronutrients that were documented to be lacking in Mexican children was formulated in a supp lement and given to Mexican children over a period of 12 mo in a longitudin al, placebo-controlled, supplementation design. Children in the low and med ium socioeconomic status grew about 1 cm more than similar children in the placebo group. This difference was not found in children of high socioecono mic status. It is suggested that, in most cases, growth stunting is associa ted with marginal deficiencies of several micronutrients and that in popula tions with multiple micronutrient deficiencies, the effect on linear growth of supplementation with single nutrients will not be significant. Suppleme ntation 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.