Zinc supplementation reduced morbidity, but neither zinc nor iron supplementation affected growth or body composition of Mexican preschoolers

In rural Mexico and in many developing countries micronutrient deficiencies, growth stunting, and morbidity from infectious diseases are highly prevalent in young children. We assessed the extent to which growth stunting could be reversed and the number of infectious disease episodes reduced by zinc and/or iron supplementation. In a double-blind, randomized community trial 219 Mexican preschoolers were supplemented with either 20 mg Zn as zinc methionine, 20 mg Fe as ferrous sulfate, 20 mg Zn + 20 mg Fe, or a placebo. After 12 mo, plasma zinc increased significantly in the two zinc-treated groups, and plasma ferritin was significantly higher in the two iron-treated groups. There was no effect of treatments on growth velocity or body composition. Children in both zinc-supplemented groups had fewer episodes of disease (zinc alone, 3.9 +/- 0.3; zinc + iron, 3.7 +/- 0.4; placebo, 4.6 +/- 0.5; P < 0.03), including diarrhea (zinc alone, 0.7 +/- 0.1; zinc + iron, 0.8 +/- 0.1; placebo, 1.1 +/- 0.2; P < 0.01). Zinc and zinc + iron supplements reduced morbidity but had no effect an growth or body composition.