Zinc, Iron Supplementation Better Individually than Combined for Infants

UMEA, Sweden--Scientists compared the effects of combined iron and zinc supplementation in infants with the effects of iron and zinc as single micronutrients on growth, psychomotor development and incidence of infectious disease.

In the community-based, randomized, controlled trial, published in the September issue of the American Journal of Clinical Nutrition, (80, 3:729-736, 2004) (www.ajcn.org), 680 Indonesian infants were randomly assigned to daily supplementation with 10 mg iron (Fe group), 10 mg zinc (Zn group), 10 mg iron and 10 mg zinc (Fe+Zn group), or placebo from 6 to 12 months of age. Anthropometric indexes, developmental indexes (Bayley Scales of Infant Development; BSID), and morbidity were recorded.

At 12 months, two-factor analysis of variance showed a significant interaction between iron and zinc for weight-for-age Z score (a measure of the distance in standard deviations of a sample from the mean), knee-heel length, and BSID psychomotor development. Weight-for-age Z score was higher in the Zn group than in the placebo and Fe+Zn groups, knee-heel length was higher in the Zn and Fe groups than in the placebo group, and the BSID psychomotor development index was higher in the Fe group than in the placebo group. No significant effect on morbidity was found.

The study indicates single supplementation with zinc significantly improved growth, and single supplementation with iron significantly improved growth and psychomotor development, but combined supplementation with iron and zinc had no significant effect on growth or development.

The scientists concluded combined, simultaneous supplementation with iron and zinc in infants cannot be routinely recommended at the iron-to-zinc ratio used in this study.