Tuesday, November 30, 2010

Vitamin D Foolishness

The NY Times reports on a new study about the level of vitamin D we should ingest. 

The problem with the aproach taken, which seems to be the usual "take this much a day", is that it doesn't address what the natural level of vitamin D ought to be. 

That's not entirely correct.  They do address the "natural" level of vitamin D, and admit that they have no idea whatsoever what it might be.

The report is essentially taking a "take this much because we know it prevents rickets" aproach, and the recommendations are all based on someone who gets "minimal" sun.  They mention several times the imaginary link between sun exposure and skin cancer as a justification for this approach.

I don't find this compelling.  What the report boils down to is: "In 100 years, since we started adding vitamin D to food, we've never bothered to figure out what the "natural" level should be."  So keep taking our advice.

I'll continue avoiding linoleic acid, which has a clear link to skin cancer, and getting regular doses of good, old-fashioned sun.  I supplement in the winter.  I'll note that, excluding sun exposure, I supplement probably less than what they recommend on a year-round basis, but my sun exposure over the summer put my serum vitamin D levels at more than four times this report's recommendation.  (52 ng/mL vs. 12 ng/mL.)  In fact, my body's natural production of D over the summer when I did not supplement at all leaves me in the category they describe as, "There may be reason for concern at serum 25OHD levels above 125 mnol/L (50 ng/mL)."  So I guess my body is trying to poison itself with vitamin D.  How unfortunate.

I think that following this report's advice is a good path to a far-lower than "natural" level of vitamin D in your system, which does not strike me as a conservative approach.

You take the risk that they're wrong:

"The established function of vitamin D remains that of ensuring bone health, for which causal evidence across the life stages exists and has grown since the 1997 DRIs were established (IOM, 1997).  The conclusion that there is not sufficient evidence to establish a relationship between vitamin D and health outcomes other than bone health does not mean that future research will not reveal a compelling relationship between vitamin D and another health outcome."

P.S.: My vitamin D experiment.  I think letting your body do what it's supposed to do is generally the wiser course than trying to tweak it based on the medical professions' grossly imperfect knowledge.