Tuesday, November 30, 2010

Vitamin D (update)

Today's Globe has this story about a new report on the recommended daily levels of vitamin D. The story is premised on this report published today by the Institute of Medicine of the National Academies.

The Institute's report, which was undertaken at the request of the US and Canadian governments, looked at both calcium and vitamin D. As I have noted in my previous posts on vitamin D, it is interesting to follow how things develop with this vitamin as an anti-aging intervention (that perhaps mimics the effects of CR) would likely face similar challenges.

The first challenge: figuring out what constitutes a safe and effective dose.

There are dangers with being too bold and with being too cautious. Prescribing people to take very high doses of a chemical (even a "natural" one) could be harmful. And yet prescribing people take a very low dose could also be harmful in that it won't realize the health benefits of a higher dose. How do we reasonably balance these different possible harms and benefits?

These concerns are what we see in this report on vitamin D. The recommended dietary allowance of vitamin D has been raised to 600 IU/day. This triples the recommended levels. Health Canada had prescribed that 200 IU/day were recommended, and that this level could be reached by simply drinking two cups of milk a day. But the new, higher levels will mean some people should take a daily supplement.

In addition to revising recommended daily dosage of vitamin D, this report has also increased the upper intake level from 2000 IU to 4000 IU. The purported benefits (lower rates of internal cancers) of taking higher doses of vitamin D is, at this stage, inconclusive. This presents a second challenge: what to do when the findings are still inconclusive?

Daily dosages of vitamin D between 600 IU and 4000IU are still an "unknown" in terms of health benefits. These levels have been deemed safe, but does a dosage above 600 IU confer any health benefit? And what is it reasonable to do when such uncertainty exists? Should one take a higher dose, a dose that is deemed safe, just in case it has benefits? Or should one wait to see if conclusive evidence emerges about the alleged health benefits before increasing one's dosage? It's a tricky dilemma. I have my own views on this issue, but I'll leave it up to readers to make their own decisions about what levels of vitamin D they should take.

Now that the vitamin D max dosage has been increased, more studies on their purported health benefits will take place. So it will be interesting to see how things unfold in the years to come.