Zinc supplements: more research needed
although people in developing countries often lack zinc in their
diets, taking supplements during pregnancy could harm the early
mental development of their children.
A study in this week's issue of The Lancet suggests that pregnant women in developing countries who are given zinc supplements may in fact be harming their children's chances during early mental development.
Previous studies have shown that young children need zinc for proper mental development.The authors noted that 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, but a follow-up study revealed the negative effects the mineral had on the infants.
In the follow-up study, Sally Grantham McGregor and Jena Habadani from the Institute for Child Health in London, UK, and colleagues from the International Center for Diarrhoeal Disease Research, Bangladesh, assessed the same infants at 13 months old to investigate the effect of antenatal zinc supplements on their development and behaviour.
The researchers assessed the mental development of 168 infants (whose mothers received either 30mg per day of zinc or a placebo during pregnancy). Infants in the placebo group had higher scores for both mental and psychomotor development and zinc supplementation had no significant effect on behaviour or growth. The children's nutritional status was poor, according to the authors, with weight-for-age at testing strongly related to development.
Commenting on the results, Sally Grantham McGregor said: "Undernutrition is generally accepted to be detrimental to children's development, and our findings emphasise the serious nature of the problem in populations with high proportions of underweight children."
She continued: "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."