James K. Rone, MD, FACP, FACE

Is Vitamin D3 better than D2? Is Dr. Mercola Right?

April 2, 2014

Tags: Vitamin D

A patient sent me a letter asking if she should stop taking her ergocalciferol (Vitamin D2) and take Vitamin D3 instead, as she had read an online item from Dr. Mercola about Vitamin D. I read that and also reviewed this subject in a recent major endocrine text and a recent major nutrition text. The endocrine text simply said there was no difference in how D2 and D3 are used by and affect the body and said nothing more about it. The nutrition text presented a large amount of information, in great detail about many studies, less than 20 years old, stating, in effect that there was no difference. It went on however to discuss in just as much detail recent studies, since 2000, suggesting that there might be differences.
--What I came away with is that the subject is very complicated and still up for debate.
--What I can safely say is that there is NOT widespread agreement among medical and nutritional experts that Dr. Mercola's position is correct.
--I can also say that his presentation is overly simplified, and incomplete. There are studies saying what he claims they say, but there are others saying something different and he leaves that part out.
--I should point out that Dr. Mercola is widely considered to be a quack. I am not calling him a quack--I don't know enough about him--some people disagree with me too. I suggest Googling "Dr. Mercola quack" and read that stuff before deciding who to listen to. Also, he is a family practice doctor, not an endocrinologist or nutritionist--that doesn't make him wrong, but it does mean he isn't a board-certified expert on Vitamin D
--Now, he claims D2 doesn't raise Vit D levels as well as D3--I've personally taken both in roughly equal amounts and they've both kept my levels the same and the D2 brought mine up from clearly low levels that I started with. The labs of the patient in question show the same thing, and her PTH and Ca++ levels are normal suggesting her D2 is working.
--Now, I have nothing against D3--I take it--only because it's cheap and available over the counter--not because of any of this.
--my suggestion to this patient, because she is on a very large dose of D2, was that we stick with the 50,000 D2 caps--she'll be taking a lot of pills if we go with the lower doses D3 is available in.
--I offered to let her try weaning the D2 down and if we get her to the point that a once daily D3 would easily do the trick, I'd be happy to switch her. It's always reasonable to try getting away with the least medicine that does the job.

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