Like it or not, winter is here in Saskatchewan and vitamin D synthesis from sunlight is again negligible (even if we were brave enough to stand naked outside for an hour at noon). In past columns on Vitamin D I always recommended D3 over the frequently prescribed D2 form. Two studies published this year compared these two forms of vitamin D.
“Vitamin D supplementation for prevention of mortality in adults”, [www.ncbi.nlm.nih.gov/pubmed/21735411] published in July looked at 50 randomized trials with 94,000 participants over an average of 2 years. Of the 50 studies, 32 used D3 and 12 used D2. The remaining studies used two other forms of vitamin D – alfacalcidol and calcitriol. The authors found that D3 showed a significant decrease in mortality (deaths of participants from all causes) while the other forms had no significant effect.
Other findings in this meta-analysis were: that alfacalcidol and calcitriol increased the risk of hypercalcemia (excess blood calcium), and that D3 combined with calcium increased the risk of kidney stones. [Drinking sufficient water and taking vitamin K2 might alleviate the kidney stone risk.]
The other study “Vitamin D(3) is more potent than vitamin D(2) in humans” published in March, [www.ncbi.nlm.nih.gov/pubmed/21177785] compared the potencies of D2 and D3. This was a small trial involving 33 healthy adults given 50,000 units weekly of either D3 or D2 (because D is a fat soluble vitamin, it can be taken in weekly doses instead of daily). After 12 weeks vitamin D levels were measured in blood and subcutaneous fat. The study concluded that D3 was 87% more potent than D2 in raising blood levels, and produced 2 to 3 times the amount of stored vitamin D in fat. The study concluded: “Given its greater potency and lower cost, D3 should be the preferred treatment option when correcting vitamin D deficiency.”
This article is intended for educational purposes only; for medical advice consult your licensed health practitioner.