More than 60 years ago, based on the science of the time (science that has stagnated for 60 years), Dr. E. Orbermer of Italy wrote the following:
“Until further experimental evidence, adequate and incontrovertible, is made available, I submit that we should play for safety. In a climate like that of England every pregnant woman should be given a supplement of vitamin D in doses of not less than 10,000 IU per day in the first 7 months, and 20,000 IU (per day) during the 8th and 9th months.”
The “adequate and incontrovertible evidence” that Dr. Orbermer wanted, to a certain extent, is finally here, 60 years later. As it has to do with developing human beings, it could not be more important. The study is the highest standard of proof, a randomized controlled trial, conducted by Professor Bruce Hollis and colleagues at the Medical University of South Carolina. They took 350 pregnant women, gave 1/3 of them 600 IU/day, 1/3 of them 2,000 IU/day, and 1/3 4,000 IU/day. Then they waited to see, among many things, which group would produce infants with at least 20 ng/ml of vitamin D in their blood, the lowest limit the 2010 Food and Nutrition Board (FNB) says is needed for good fetal health.
Hollis BW, Johnson D, Hulsey TC, Ebeling M, Wagner CL. Vitamin D supplementation during pregnancy: double-blind, randomized clinical trial of safety and effectiveness. J Bone Miner Res. 2011 Oct;26(10):2341-57. doi: 10.1002/jbmr.463
Surprise surprise, only the 4,000 IU/day pregnant women group even approached the minimal safety level of 20 ng/ml in their infants. Furthermore, the 2010 FNB recommendations of vitamin D in prenatal vitamins would have left 50% of the White women and 80% of the Black women with fetuses below 20 ng/ml.
However, Professor Hollis found something else, something potentially much more important. He found that the average fetus in the USA is starved for enough building blocks for his or her mother to make adequate activated vitamin D to ship to the baby; activated vitamin D that is probably used for microscopic organ development, such as in the brain.
Activated vitamin D in pregnancy is mysterious. It appears the mother makes it in her kidney (maybe some in her placenta) at levels up to 3 to 4 times normal (without maternal hypercalcemia) and ships it across to the fetus. This only happens if the mother has enough of this vital steroid hormone in her body to ship to the fetus and most mothers do not. If she can’t make it, she can’t ship it maximally, and the 38 fetal organs depending on activated vitamin D to fully develop must do the best they can do with inadequate amounts of this steroid. Of course, none of this applies to mothers who frequently sunbathe, or who take 5,000 IU/day while they are pregnant.
To quote Professor Hollis: “These findings suggest that the current vitamin D (requirements for pregnancy, currently 600 IU/day) issued in 2010 by the Food and Nutrition Board should be raised to 4,000 IU of vitamin D per day so that all women, regardless of race, can attain optimal nutritional and hormonal vitamin D status throughout pregnancy.”
The Vitamin D Council agrees and considers this an important study in support of why adults and pregnant women need at least 4,000 IU/day to elevate blood levels and improve fetal health and birth outcomes. Although there are no trials that support taking more, the Vitamin D Council believes 5,000 IU/day is equally safe and would be more effective at maintaining adequate fetal blood levels of vitamin D.