Randomized controlled trial of the effect of zinc supplementation on the mental development of Bangladeshi infants

Background: Zinc deficiency is thought to be common in young children in de veloping countries and some data suggest that it may detrimentally affect c hildren's development. Objective: Our goal was to assess the effect of zinc supplementation on the developmental levels and behavior of Bangladeshi infants. Design: This was a randomized, double-blind, controlled trial conducted in Dhaka, Bangladesh. Three hundred one infants aged 1 mo were randomly assign ed to receive either 5 mg elemental Zn or placebo daily for 5 mo, and subse quent growth and morbidity were observed. For the present study, developmen tal levels were assessed in a subsample of 212 infants at 7 and 13 mo of ag e with use of the Bayley Scales of Infant Development, and the infants' beh avior during the tests was observed. The children's social backgrounds, wei ghts, and lengths were also recorded. Results: The children's nutritional status was generally poor. The zinc-tre ated group had slightly lower scores on the mental development index of the Bayley Scales than did the placebo group (beta =3.7, SE=1.3, P<0.005). Thi s effect remained significant when nutritional status and social background were controlled for. No other significant differences between groups were noted. Conclusions: The mental development index scores of the zinc-treated group were slightly but significantly lower than those of the placebo group. This finding may have been due to micronutrient imbalance. Caution should be ex ercised when supplementing undernourished infants with a single micronutrie nt.