Low vitamin D linked to increased risk of heart attack, death
■ Studies add to the data indicating that not having enough is unhealthy. Physicians are calling for more guidance.
By Victoria Stagg Elliott — Posted July 14, 2008
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The weight of evidence connecting low vitamin D levels with poor health is getting heavier.
One study published in the June 9 Archives of Internal Medicine linked low levels of this vitamin in men to an increased risk of myocardial infarction. The other, in the June 23 issue of the same journal, found that being deficient in this vitamin more than doubled the risk of death from any cause.
"The evidence is just becoming overwhelming," said Dr. Harald Dobnig, lead author on the second paper and professor of internal medicine at the Medical University of Graz in Austria.
These are the latest studies to identify low vitamin D as a significant health risk. Additional analyses completed on the cohort studied by Dr. Dobnig and due to be published in the future show that vitamin D status also influences the risk of cancer and stroke.
"Vitamin D seems to be very important," said Michael F. Holick, MD, PhD, a professor of medicine, physiology and biophysics at Boston University School of Medicine. He is researching the effect of supplementing with large amounts of vitamin D. "Every tissue and cell in your body has a vitamin D receptor. Mother Nature is very clever and is not going to make something that isn't used."
In response, physicians more frequently are assessing vitamin D levels in the blood, talking to patients about taking various supplements, or taking the supplements themselves. Still, many issues remain challenging. For instance, most physicians shy away from recommending sun exposure, a significant vitamin D source, because of the skin cancer risk. It is unclear how much supplementation is needed to bring blood levels up to a number that will make a difference.
Also, while compelling evidence appears to support the notion that low vitamin D is unhealthy, less data exist to signal that increasing consumption will improve health status. Studies investigating this premise are forthcoming. Researchers are pursuing vitamin D supplementation as possible treatments for a wide range of health issues from obesity to diabetes to various forms of cancer.
"Before we advocate widespread supplementation with vitamin D, [we need] the initiation of large randomized controlled intervention trials," Dr. Dobnig said.
There's also the question of who should have their levels measured. Testing can be expensive, and some experts say vitamin D deficiency is so common that everyone should be encouraged to increase their intake. Others are testing routinely and taking action in response to the results, but physicians increasingly are calling for evidence-based guidance.
"We have got some very positive information about vitamin D to prevent cancer, heart disease and skin conditions, and yet we are unsure what a safe dose is. This is really a hot-button issue that patients are very curious about," said John S. Antalis, MD, a family physician from Dalton, Ga., who spoke for the Medical Assn. of Georgia when this subject came up in June at the American Medical Association Annual Meeting in Chicago.
Meanwhile, in an effort to provide some direction on this issue, Dr. Holick is chairing an Endocrine Society committee that is writing a clinical practice guideline on the subject. The document is expected out before the end of the year. The AMA's Council on Science and Public Health also is writing a report due to be released at the AMA's June 2009 meeting.
"Hopefully, we can clear up some of the confusion," said Sandra Adamson Fryhofer, MD. She is an Atlanta internist and a CSAPH member.
In addition, the AMA wants the Institute of Medicine's Food and Nutrition Board to re-evaluate the recommended intake for vitamin D, according to policy passed at AMA Annual Meeting last month in Chicago.
The paper published in the June 9 Archives of Internal Medicine was funded by the National Institutes of Health, although one of the authors is a consultant for a manufacturer of assays that determine vitamin D status. The paper published in the June 23 issue was authored by a group that has received unrestricted grants from several companies that make prescription-strength vitamin D supplements.