In December 1947 Dr. E Obermer wrote in the British Medical Journal: “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 during the 8th and 9th months.”
Nearly 60 years later, an important piece of that evidence has finally arrived. A randomized controlled trial conducted at the Medical University of South Carolina and published in December 2011 in the Journal of Bone and Mineral Research divided 350 pregnant women into groups given 400, 2,000 and 4,000 IU of vitamin D daily. After the births, their babies were tested for blood vitamin D levels. The target was 20ng/ml, the minimum considered adequate for healthy fetal organ development by the U.S. Food & Nutrition Board. The 4,000 IU group came closest but still fell short of achieving the target in all cases. The study concluded “…vitamin D supplementation of 4,000 IU/d for pregnant women is safe and most effective in achieving sufficiency in all women and their neonates regardless of race, whereas the current estimated average requirement is ineffective at achieving adequate circulating 25(OH)D concentrations, especially in African Americans.”
Both the American FNB and Health Canada have set the RDI for vitamin D during pregnancy and lactation at 600 IU per day. Health Canada’s concern with higher intakes is that “too much vitamin D…can lead to calcification of the kidney and other soft tissues including the heart, lungs and blood vessels.” As I have discussed in previous columns, this problem is now known to be the result of insufficient vitamin K2. If the dietary regulators are still unconvinced, I would like to see the study repeated, this time with vitamin D intakes of 4,000 to 10,000 IU, and with the addition of sufficient K2. Perhaps Dr. Obermer, writing 59 years ago, wasn’t so far off the mark after all.
Source: Vitamin D Newsletter March 21, 2012, by John Cannell, Vitamin D Council.
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