Vitamin D Supplementation: State of the evidence?

Answered on September 12, 2014
Created November 30, 2010 at 12:58 PM

I've seen recommendations for Vitamin D supplementation from many respectable sources (including Kurt of Panu and Peter of Hyperlipid, among others).

This morning I read that "Extra Vitamin D and Calcium Aren???t Needed, Report Says" in the New York Times. The article mentions:

Evidence also suggests that high levels of vitamin D can increase the risks for fractures and the overall death rate and can raise the risk for other diseases.

Does anyone have primary sources or other information relating to the Times' discussion? I'm curious as to the precise nature of these supposed risks.

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on November 30, 2010
at 03:43 PM

First, I wouldn't recommend calcium supplements.

Second, unless you have really, really good evidence, you just can't argue with a randomized placebo controlled trial finding that 1100IU of supplemental vitamin D (and calcium) prevented 77% of cancers, after excluding the first year (which is standard in cancer prevention trials). Here's the study from 2007 with the findings I described: http://www.ajcn.org/content/85/6/1586.full.

Especially giving the mountain of consistent epidemiological evidence, such a strong finding can only be refuted with another larger placebo controlled trial of superior design. They are conducting one now and we will have results in a few years.

That said, I think that some people take it too far, exceeding levels that are physiologically possible. Kurt Harris, for example, incorrectly states that people can obtain levels up 100-120 ng/ml from the sun when the number is more like 50 ng/ml. That's dangerous mis-reporting on his part and naive acceptance of fanciful claims on the pat of his readers. (In fact, since he's a pretty smart guy, I'd guess he probably just made a units error and meant nmol/L).

Also, it's hard to gauge vit D supplementation in isolation. Vit K, vit A, calcium, and magnesium status all play a part, along with numerous other nutrients.

In the face of the uncertainty, this is as area where it really does make sense to let evolution/paleo theory be your guide. Maintaining levels at 40-50 ng/ml is quite natural, in the tropics. We can assume that vit K and vit A levels would also be somewhat high, since both originally derive from green and colored vegetables, respectively, and indirectly from the animals that eat them. Thus, in the northern summer or in the tropics, moderately high vit D levels would likely have gone hand in hand with decent intakes of vit K and vit A, as well as magnesium. I don't think calcium supplementation makes much sense in this context.



on November 30, 2010
at 02:46 PM

The primary sources are available for free here, see page 297:


As a disclaimer, I worked on the team synthesizing evidence for this report. Thus I can't give a real opinion (not that I have a good one) other than providing a link to the report. That being said, recommendations for upper tolerable nutrient intake are for populations. You as an individual may be different. In addition, the evidence for benefits is limited, and the evidence for harms is much more scarce.



on November 30, 2010
at 06:40 PM

Hmm the only way both together increase risk of fractures I'm aware of is if you don't take any of the other bone health/ D co-factors (E.G. if you don't have enough MG and K2 etc.., the imbalance with D3+ calcium causes either more of the other minerals to be leeched from your bones or your bones only get harder and more brittle instead of more elastic), conversely if your levels of D and all the co-factors are high enough your daily req for calcium goes down to something like 400mg.

Hmm looking at what Kamal Linked I see some studies just say D, some used D2 and some say D3 but not the form (from what I understand the dry tablets can have zero effect sometimes, and the liquid form of D3 is most effective, and in general D3 is the effective one) also I see most calcium supplements are listed as just calcium, or calcium carbonate (which is like MG oxide as in one of the worst absorbed forms?).

So Multiple studies, many different forms of D without actually listed the type of D itself, many different types of calcium and where listed its the cheapest and worst version for the human bodies use, and no mention of the other variables of levels/testing of all the other factors for D etc.

Gives me more questions than answers actually.

D co-factors below, with Mg being most important:

  • magnesium
  • zinc
  • vitamin K2
  • boron
  • a tiny amount of vitamin A

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