Last year I bragged about vitamin D and the evidence showing benefits in multiple arenas, especially for fighting colds and flu. I even started taking 2,000 IU a day of vitamin D3.

But now…one wonderfully annoying thing about medicine is that one headline will say “medicine A is great for disease X”, but wait a couple years and another famous journal will contradict it — thus frustrating doctors and confusing the public.

And now, of course, we have a long-awaited publication from the highly-esteemed U.S. Institute of Medicine, which last November published their findings about vitamin D and calcium. The IOM is very official and their papers are usually considered top quality standards of care. In this case, they were not very enthusiastic about vitamin D supplements for most people, and concluded that actual vitamin D deficiency is not so common. They specifically recommended only 600 IU a day supplement for people aged 1-70 years;  over 70 years needs 800 IU a day. That’s it; no mega-doses, not even 1,000 IU, for anyone. Not only that, but anyone taking more than 4,000 IU a day is not only getting no additional benefit but they increase their risk of kidney stones and other issues (how many of you are taking 5,000 IU a day?). Here’s the table of their official recommendations:

This more cautious review came just a couple weeks after another well-regarded review from Canada which was much more enthusiastic about supplements and recommended 400-1,000 IU for most people, and 2,000 IU or more for “high risk” people such as people prone to osteoporosis.

So, what do we do now? We have two large and well-esteemed groups reviewing the same research papers and coming up with different conclusions.

What Will I Do?

I do respect the Institute of Medicine, and perhaps the Canada study is a bit too local to apply to other areas. So I would tend to stick to the IOM’s more conservative official recommendations as the new standard of care.  But I also still like those previous papers I mentioned last year about 1,200 IU of vitamin D3 helping cut down on colds and flu by 42%, so I will personally continue to take my 2,000 IU of vitamin D3. Is the dose too high? Maybe, probably — but just wait a couple years and another study may change things yet again. Plus, 2,000 IU doesn’t seem to raise the risk of kidney stones. So, for me, the possible benefits outweigh possible harms.

However, I do think there are some take-home points for the general public:

• All children should be taking a supplement of 400 IU a day, which should also include calcium (especially for girls!), mostly for bone health
• People taking over 5,000 IU a day are wasting their money and also increasing their risk for kidney stones
• Many healthy people may not need it, but if a small dose of 1,000 IU cuts down on your winter colds and flu, then why not take it?
• Blood testing for vitamin D levels can be done but still isn’t very practical, cost-effective or useful

Those of you who want to read more can read the excellent New York Times review this week about vitamin D.