Vitamin D is safe and effective in healthy pregnancies

Healthy pregnant women can benefit from taking 4,000 IU of vitamin D daily without harming themselves or their baby, a large, randomized, double-blinded clinical trial from the Medical University of South Carolina has concluded.

The study, published online June 27 in the Journal of Bone and Mineral Research randomized 494 women with a singleton pregnancy to receive 400 IU (the standard dosing regimen), 2,000 IU (the previous daily upper limit), or 4,000 IU of vitamin D₃ from 12 to 16 weeks’ gestation until delivery. Three hundred fifty of the women enrolled completed the study. Researchers evaluated maternal and neonatal circulating 25(OH)D at delivery and, secondarily, attainment of at least 80 nmol/L of 25(OH)D and the 25(OH)D level needed for maximum production of 1,25(OH)₂D.

Women receiving 4,000 IU of vitamin D and their babies had the highest levels of 25(OH)D at 1 month before delivery and at delivery and the greatest proportion of vitamin D sufficiency. The 3 supplementation groups showed no difference on any safety measure, and no adverse events were associated with supplementation or circulating 25(OH)D levels. The findings were independent of race and ethnicity.

Circulating 25(OH)D directly affected circulating concentrations of 1,25(OH)₂D throughout pregnancy. Women who received 4,000 IU produced the most 1,25(OH)₂D in all strata.

“These findings suggest that the current vitamin D EAR [estimated average requirement] and RDA [recommended daily allowance] for pregnancy women issued in 2010 by the Institute of Medicine should be raised to 4,000 IU vitamin D per day so that all women regardless of race attain optimal nutritional and hormonal vitamin D status throughout pregnancy,” the authors of the study write. The Institute of Medicine recommends an EAR of 400 IU and an RDA of 600 IU for pregnant women. Researchers found the recommended EAR to be comparatively ineffective in achieving adequate circulating 25(OH)D, especially in African American women.