Vitamin D - How Strong is the Evidence? Part 3

How ironic.  What with all the articles that get published along w/the upcoming holidays, I forgot that I had started this month writing about vitamin D for 3 consecutive days.  Well, I tried to remind everyone that while vitamin D is the latest bandwagon upon which everyone appears to be hitching their non-osteoporotic health conditions, based upon observational studies, correlation is not causation.

The more conservative Endocrine Society published their clinical practice guideline on the evaluation, treatment & prevention of vitamin D deficiency back in July in their JCEM.  They're comfortable with the use of 25OH vitamin D as the initial screening assay but don't recommend its use in those not at risk for deficiency.  

On the surface, this is a reasonable statement but realistically, there are very few of us who are low risk and get enough sun exposure daily throughout the year without an sunscreen or sunblock.  Studies of the general population in traditionally sunny geographic areas such as Arizona, Florida & Hawaii demonstrate a higher than expected rate of vitamin D deficiency.

Ironicially, a systematic review & meta-analysis published in the same issue of JCEM found no cardiovascular benefit from vitamin D in 51 randomized controlled trials.  And a quick summary published earlier this week reviewed the paucity of randomized controlled trials demonstrating non-osteoporotic benefit.

So what's the take home message?  Well, it depends upon whether you see the proverbial glass as half full or half empty.  If you're only comfortable with the results of randomized controlled trials, you'll have a ways to wait.  On the other hand, if you're comfortable with the current set of observation studies (despite the lashing received from the public & lay press over the last several years), start popping vitamin D supplements.  The only problem is that we don't know how much is enough and we now have to worry about poor manufacturing leading to toxicity.

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