High intakes of vitamin D during pregnancy are safe

According to a new US study, vitamin D supplementation of 4000 IU /day for pregnant women is safe and most effective in achieving sufficient levels in women and their newborns.

In the randomized controlled trial, 494 women with a singleton pregnancy were assigned to receive 400, 2000, or 4000 IU of vitamin D3 per day at 12 to 16 weeks' gestation until delivery (1). Blood samples were taken to measure the 25-hydroxyvitamin D [25(OH)D] concentrations in the mothers and the newborn at delivery. The study results showed that the mean 25(OH)D concentrations in the groups were significantly different at delivery and one month before delivery, with the highest levels in the 4000 IU group. No adverse events were attributed to vitamin D supplementation or circulating 25(OH)D levels.

The researchers concluded that vitamin D supplementation of 4000 IU /day for pregnant women is safe and most effective in achieving sufficient levels in all women and their neonates, regardless of race. However, the current estimated average requirement of 600 IU/day during pregnancy is comparatively ineffective, especially in African Americans, in achieving adequate circulating 25(OH)D concentrations of 80 nmol/L or greater.

1. Hollis B. W. et al. Vitamin D supplementation during pregnancy: Double-blind, randomized clinical trial of safety and effectiveness. JBMR. Online publication October 2011.