Prenatal Zinc Supplementation Could Impair Childhood Mental Development

Authors of a study in this week’s issue of THE LANCET caution that the provision of zinc supplementation to pregnant women in developing countries could impair the early mental development of their children. Zinc deficiency is common in developing countries due to a diet that is low in animal protein and high in fibre. Supplements given to Bangladeshi pregnant women have previously been shown to improve infant growth and to reduce susceptibility to infectious diseases. In a follow-up study, Sally Grantham McGregor and Jena Habadani from the Institute for Child Health, London, UK, and colleagues from the International Center for Diarrhoeal Disease Research, Bangladesh, assessed these infants at 13 months of age to investigate the effect of antenatal zinc supplementation on infant development and behaviour.

The mental development of 168 infants (whose mothers received either 30 mg per day of zinc or placebo during pregnancy) were assessed. Infants in the placebo group had higher scores for both mental and psychomotor development. Zinc supplementation had no significant effect on behaviour or growth. The children’s nutritional status was poor—weight-for-age at testing was strongly related to development.

Sally Grantham McGregor comments: “Undernutrition is generally accepted to be detrimental to children’s development, our findings emphasise the serious nature of the problem in populations with high proportions of underweight children. Since zinc supplementation in infants has a beneficial effect on growth and morbidity, and supplementation of mothers was associated with reduced morbidity in low birthweight infants in this study, our findings complicate policy making…Undernourished pregnant women obviously require more than zinc alone. The next step would be to examine the effect of more comprehensive supplementations to improve maternal nutritional status during pregnancy on a broad range of outcomes including infants’ development.”

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