Most experts recommend that pregnant women take a daily supplement of 400 units of vitamin D. Now a randomized clinical trial suggests that a much larger dose may be beneficial for children’s bone health. The study, in JAMA Pediatrics, randomized 517 women to take either a 2,400-unit vitamin D supplement or a placebo from 24 weeks of pregnancy until one week after birth.
In addition, all the women were advised to take a 400-unit vitamin D supplement, in line with Danish health recommendations.
The researchers followed the offspring with periodic bone scans through age 6, recording bone density and evidence of fractures. Over all, children whose mothers took 2,800 units had significantly higher bone density at age 6 than children in the placebo group. The effects were particularly robust in women who were initially deficient in vitamin D and in those who gave birth during the winter, when sunlight levels are lower and vitamin D blood levels tend to drop.
About 7 percent of children whose mothers took the high dose suffered bone fractures through age 6, compared with 11 percent in the placebo group. High doses had no effect on birth weight, or on the height or weight of the 6-year-old children.
“There is no concern about safety, and no risk of side effects” at the doses given, said the senior author, Dr. Hans Bisgaard, a professor of pediatrics at the University of Copenhagen. “We have the data suggesting it’s useful, so let’s use it. Health begins early in life. That’s where we can make a difference.”
Brustad N, Garland J, Thorsen J, et al. Effect of High-Dose vs Standard-Dose Vitamin D Supplementation in Pregnancy on Bone Mineralization in Offspring Until Age 6 Years: A Prespecified Secondary Analysis of a Double-Blinded, Randomized Clinical Trial. JAMA Pediatr. Published online February 24, 2020