Individual studies of the effect of zinc supplementation on childrens growth have yielded inconsistent results due to unpredictable factors such as the availability of zinc in the local diet and the pre-existing zinc status of the study subjects. In order to provide a systematic qualitative review of findings regarding the efficacy of zinc supplementation, Brown et al. consolidated results from multiple studies from countries around the world in a meta-analysis published in the American Journal of Clinical Nutrition. They found that, overall, zinc supplementation of infants and children produced positive growth responses in height and weight.
Based on a standard set of inclusion criteria, 33 studies on zinc supplementation of children aged newborn to 10 years that were published between 1976 and 2001 were identified for the meta-analysis. Thirteen studies were conducted in Latin America or the Caribbean, 8 in Asia, 8 in North America or Europe, and 4 in Africa. Zinc supplementation had a positive growth effect on both height and weight. Infants and children who were initially stunted or underweight realized the greatest benefit from zinc supplements. Zinc supplements significantly increased serum zinc concentrations, which has important public health implications because serum zinc increases are routinely used in field studies as a practical indicator that supplements have been delivered, consumed, and absorbed by the recipients.
Martorell, in an accompanying editorial, points out that in poorer countries where dietary quality is uncertain, the nutritional needs of young children are unlikely to be met even though enough food is consumed to meet energy requirements. Providing zinc-fortified complementary foods in such circumstances may be the most cost-effective approach to assuring adequate growth for infants and children in developing countries.