Treating vitamin D deficiency requires caution

Vitamin D seems to be all the rage in medicine these days. A family physician colleague commented to me recently that the laboratory test for vitamin D deficiency is becoming the most frequently ordered test in his practice.

This clinical bandwagon is likely a response to data from multiple recent studies that found low vitamin D levels in the majority of children and adults of all ages. While vitamin D has always been thought to play an important role in keeping bones strong, researchers are suggesting that low levels may increase one’s risk for a variety of diseases, including cancer and cardiovascular disease.

Before you go out to your local drugstore to buy mega-doses of vitamin D supplements, though, there are at least two good reasons to proceed with caution.

First, association does not always translate into causation. In other words, just because people with a low (or high) level of a nutrient are more likely to suffer from a particular illness doesn’t mean that the abnormal level caused the illness, nor does it mean that restoring a normal level will cure it. For example, studies have showed that high homocysteine levels are associated with an increased heart attack risk. When I was in residency training, cardiologists routinely prescribed folate supplements to patients who had had heart attacks in order to lower their homocysteine levels and reduce their risk of having another heart attack. However, subsequent studies determined that lowering homocysteine levels does absolutely nothing for these patients.

The second reason to be wary of the vitamin D hype is that we’ve been down this road before, with vitamins A, B, C, and E. An editorial published recently in the American Journal of Epidemiology provides a sobering summary of initial high hopes placed in each “anticancer vitamin du jour” that were subsequently dashed by randomized controlled trials. In the case of vitamin E, high doses actually appear to be harmful.

There’s a lot we don’t know about vitamin D, as an exhaustive review of the evidence for the U.S. Institute of Medicine concluded last year. Although most studies suggest that vitamin D supplements reduce the risk of fractures and falls in older adults, it’s not at all clear what the best dose should be; in a recent study, older women taking a single large dose of vitamin D each year suffered more fractures and falls than women who didn’t.

In the meantime, there are many other things that you can do to keep your bones healthy, including regular weight-bearing exercise, not smoking, and eating a balanced diet that includes two to three servings of dairy products each day.

Kenneth Lin is a family physician who blogs at Common Sense Family Doctor.

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  • JohnnyM

    Here, Here!!! I can’t tell you how uncomfortable I am when patients demand to be placed on 50K units of Vit D, especially when I think of the Vit E fiasco. We really don’t know anything yet…remember lidocaine for PVCs with MIs? Have we not learned our lesson?

  • doc99

    I wonder if today’s increasing use of sunscreens and decreasing consumption of milk is at work here.

  • Nemo

    When I was in residency training, cardiologists routinely prescribed folate supplements to patients who had had heart attacks in order to lower their homocysteine levels and reduce their risk of having another heart attack. However, subsequent studies determined that lowering homocysteine levels does absolutely nothing for these patients.

    That’s because folate is only one part of the necessary nutrients to drive the folate cycle to convert homocysteine to methionine….one also needs adequate B12, B6 and methyl donors like choline or betaine. Interestingly enough, when all are prescribed – best through diet – homocysteine levels do fall, nutrient status does rise, and risk falls for a first or second event falls.

    An editorial published recently in the American Journal of Epidemiology provides a sobering summary of initial high hopes placed in each “anticancer vitamin du jour” that were subsequently dashed by randomized controlled trials. In the case of vitamin E, high doses actually appear to be harmful.

    You may want to go back and read the data – the mix of vitamin E matters. In various studies finding negative effects, the supplements used were alpha-tocopherol exclusively. When one uses mixed tocopherols, the results change dramatically. What we still don’t know is why!

  • Fleur

    Thats because you have to synergize vitamins and nutrients together. You can’t just isolate one vitamin and expect it to be a magical bullet. In order for vitamin D to be effective it needs to be taken along with E, A, and K vitamins as well. And you would need to check the patients other nutrient and minerals levels as well. Thats also the reason that it didn’t work in randomized, controlled studies.

  • http://www.sunarc.org William Grant, Ph.D.

    Reasoning by analogy is NOT the way to try to understand the health benefits of vitamin D. Every cell in the body has vitamin D receptors. Skin pigmentation has adapted to solar UV doses as people migrated around the world. Observational studies have developed dose-response relations for serum vitamin D levels for a variety of health outcomes including breast and coloretal cancer, influenza, all-cause mortality rates, etc. Randomized controlled trials have demonstrated effectiveness of 1000-2000 IU/d in reducing risk of influenza, all-cancer incidence, pneumonia, all-cause mortality rate, etc. For those who would like to review the evidence for vitamin D, go to pubmed.gov and search vitamin D with any other terms you wish. Oh, and don’t be so afraid of the sun, the most important source of vitamin D.

  • Anonymous

    It would not be surprising if vitamin D deficiency is up due to people listening to dermatologists saying to avoid any and all sun exposure and to dress like this whenever one goes outside.

  • http://www.BocaConciergeDoc.com Steven Reznick MD FACP

    Its great to see some common sense and perspective in the care of patients. I have been preaching the same message to my patients and colleagues and get treated like a misfit for it. We have seen Vitamin D levels reduced in a plethora of conditions. Until we can prove that restoring the Vitamin D Levels will fix the problem or prevent the disease we really should be doing research not advocating mega doses of a fat soluble vitamin. Didnt we agree to ” First Do No Harm” when we signed as physicians?

  • John S.

    I remember telling one of my teachers in high school that the more schooling I get, the more I read, the more I learn, the less sure I am about everything. And this latest vitamin D controversy adds to the confusion. It turns out all to often that what was once thought to be good for us we now discover is bad for us. And what about the hawkers of vitamins? Seems like they have exhausted all efforts to sell one vitamin supplement a new one with a fancy name is introduced.

    Sometimes I think the world and its affairs are driven mainly by marketing and greed!

  • P. W. Fisher

    It is hard to teach and old dog new tricks. In this case we might be talking about cognitive dissidence. Remember how long (about 12 years) the “experts” ridiculed those researchers who said that stomach ulcers where caused by h-pylori bacteria. I think that it is a safe bet that the MD critics have read little, if any, of the vitamin D research of past ten years.

  • jp

    I work part time in a bariatric practice and there is some consensus that correcting low levels of D is helpful for obese pts. I wish the author would have addressed this issue.

  • Sher

    As it always seems when it comes to health and especially nutrition, we are misinformed on many levels. Our doctors compare one vitamin to another never taking into account that our environment has changed the scope of what we put into our mouths to keep our bodies healthy and alive and what we are exposed to on a daily basis from a plethora of toxins. We often have well-intentioned physicians who often seem opposed to vitamins or supplements because usually they don’t understand the complex synergy of nutrition, which is, at best, lacking in this country due to overprocessed and industrialized food sources. As for Vit. D, there isn’t a “pill”, such as a supplement, that is going to “fix” what ails one. If it is cancer, you can’t take Vit D and just expect it to go away. We are not getting the sources of minerals and vitamins as we should …. over fertilizing, traveling, bad soils, etc., etc.. We must keep up with what is going on around us. Taking some extra Vit D isn’t going to hurt …. is it? It doesn’t have to be 20,000 units. So, I ask these fine doctors this: What is causing the influx of disease in this country that only gets worse as time goes on. (I still take 400 U of Vit E; I’m in my 60′s and healthy.)

  • http://www.vitamindwiki.com Henry Lahore

    Perhaps 10% of the doctors have learned that hormone D is not another vitamin fad. There are 700+ studies, 2500 items, 10 overviews, and 36 categories of vitamin D information at VitaminDWiki.com. Even 2 sections for medical professionals. Come learn and/or add as you wish