Maternal zinc supplementation improves hepatitis B antibody responses in infants but decreases plasma zinc level

The World Health Report identifies zinc deficiency as one of the major causes of disease in developing countries, and infants are at particular risk. We aimed to investigate the effect of maternal zinc supplementation on the infant's immune function in a population at risk of deficiency. In a randomized, double-blind placebo-controlled trial, mothers were supplemented either with 20 mg/day of elemental zinc (n = 20) or placebo (n = 19) at the beginning of second trimester, which continued until 6 months postpartum. Indicators of the infants' immune function measured included interleukin (IL)-7, thymic size and response to hepatitis B vaccination. Infants born from mothers receiving zinc supplements during pregnancy and postpartum had significantly lower plasma zinc (p < 0.05) but marginally higher IL-7 and antibody responses to hepatitis B vaccination (p < 0.10) than infants born from mothers not receiving zinc. Maternal zinc supplementation showed no negative impact on copper status of mothers or their infants. Maternal zinc supplementation did not influence infant thymic size, but cord blood IL-7 was found positively associated with thymus size at 1 month of age (r = 0.392) and with hepatitis B vaccine response at 6 months of age (r = 0.386). Prenatal and postnatal zinc supplementation marginally improved T cell-dependent antibody responses in infants along with IL-7, a cytokine involved in human T cell development and maintaining homeostasis.