Search This Blog

Follow by Email

Sunday, May 16, 2010

vitamin D--the controversy

In the last year vitamin D has been making headlines. It is not a new vitamin. It was first synthesized in the 1920s and deficiency of the vitamin was known to be a cause of rickets, a bone deforming disease, associated with reduction of sun exposure with the movement to crowded living conditions with inadequate sun exposure during the industrial revolution. It is important in regulating absorption of calcium in the gut and deposition of calcium in bone as well as having a role in  supporting the immune system.  Vitamin D2 can be made by plants and was added to milk and cereals in order to prevent rickets in children starting in the late 1920s.

Vitamin D is available in relatively small amounts in various foods, especially fatty fish and beef liver. Normally these food supplement the vitamin D made in the skin when we are exposed to certain wavelengths of sunlight.  Dark skinned people are less efficient at producing vitamin D from a given amount of sun exposure, which partly accounts for the fact that evolution has put light skinned peoples at the extremes of northern and southern latitudes.  Even so, in the winter at the arctic circle, there is no radiant light sufficient to allow the skin to synthesize vitamin D.

Recently data has been piling up about the benefits of vitamin D and the various forms of ill health associated with vitamin D deficiency.  A study in 2008 published in the Archives of Internal Medicine showed a higher death rate in adults with lower vitamin D levels, for instance.  Other studies have shown and increased risk of influenza and possibly cancer in patients who are vitamin D deficient. Some high profile studies have shown an improvement in fall risk and fractures in elderly patients who are given vitamin D supplements, with or without calcium, but other studies have shown no effect at all.

I practice medicine in a town which is significantly north of the equator, thus providing little sunlight of a wavelength effective for production of vitamin D in the skin during the winter.  This combined with cold temperatures means that when I check the vitamin D levels of patients at the end of the winter, about half of them are significantly deficient.  This is huge. It implies that half of the patients I test are ill in some way, are courting fractures and other vitamin D related maladies such as infections and bone pain and overall sickliness.
Just this week an article published in the Journal of the AMA by Kerrie Sanders et al studied a group of community living people, aged 70 and over, who were given a huge dose of oral vitamin D once a year with the expectation that the resultant increase in vitamin D stores would reduce falls and fractures.  The results, however, were surprising. Significantly more of the vitamin D treated patients developed falls and fractures, especially in the 3 months following receiving the large dose. Interpretation of this finding included thoughts about odd physiological responses to huge doses of vitamin D, which seems plausible, and less plausibly, that since these people felt so chipper after getting their supplement, that they were out and about more and so fell down and broke bones.

There are many issues brought up by this article, which are especially relevant in this year when vitamin D has ridden into the practice of medicine like a handsome sheriff with a white hat.

1. Do we trust laboratory tests of vitamin D levels to tell us if a person needs vitamin D supplementation?  Darker skinned people routinely have lower vitamin D levels, but aren't clearly sick because of it.  In my experience, deficient levels of vitamin D are randomly associated with skin color, diet or sun exposure, and not usually associated with overall health of the patient. I have been told that laboratory levels are not necessarily consistent from test to test.

2. How should we supplement vitamin D? The studies that have shown good effects of supplementation used daily doses of around 800 units, yet many of my patients who already take this dose daily are found to be deficient. Normally we replete vitamin D levels with 50,000 units of vitamin D twice weekly for 6 weeks, followed by recommendations to take at least 1000 units of vitamin D thereafter. Is this method wrong?

3. Is it cost effective to test for vitamin D deficiency, or should we just supplement everyone's diet with oral vitamin D? Not everyone's insurance pays for a vitamin D level and the test can run up to $150.  If we do test for deficiency, do we need to re-test to make sure the person is adequately repleted and if so, how often? If we want to achieve the goal of maximum health for minimum time , money and anxiety spent, how best should we do this with regard to vitamin D?

Vitamin D in a form that a person with a healthy liver and kidneys can use is inexpensive, but the widespread treatment of what may or may not be a disease is presently consuming huge amounts of resources of time and perceptions of health.

No comments: