Vitamin D and the Flu

Recently, there have been many articles published on the benefits of Vitamin D. Just three years ago, I would rarely test patients for Vitamin D. Now, I test Vitamin D status, and supplement accordingly, for approximately 1/3 of my patients. The Northwest's dreary winters are infamous for inducing depression. But being starved for sunlight can do more than cause low mood.

A growing body of evidence suggests Vitamin D's effects on genes are so powerful that a deficiency in Vitamin D over an extended period of time has been associated with 17 types of cancer, susceptibility to heart attack, diabetes, high blood pressure, osteoporosis, autoimmune diseases, chronic pain and other modern chronic diseases. In addition, the Pacific Northwest's high rates of multiple sclerosis may be explained, at least in part, by the lack of sunlight.

Vitamin D is an essential nutrient produced in abundance by skin exposed to the sun's rays. It is now recognized as a key player throughout the body, including the immune system. Research is now exploring the possibility that the reason for seasonal illnesses may be due to lack of sunlight in the winter months. It may be that the beneficial effect of sunlight-produced Vitamin D in the summer is the "seasonal stimulus" that keeps colds and flu at bay.

There are already a number of small studies that show taking vitamin D in sufficient quantity can be protective against colds and the flu. In one study, Adit Ginde, MD,MPH and colleagues looked at the Third National Health and Nutrition Examination survey (NHANES III) data that is collected by the National Center for Health Statistics. In this study, the authors found that Americans with the lowest vitamin D levels (less than 10 ng/ml) were about 40% more likely to have reported a recent respiratory infection than were those people whose vitamin D levels were 30 ng/ml or higher. Furthermore, those people who had asthma and the lowest vitamin D levels were five times more likely to have had a recent respiratory infection. In addition, there is preliminary evidence that vitamin D may help protect the body from viruses such as H1N1, or Swine Flu.

Vitamin D deficiency now seems to be much more common than previously recognized. While blood levels of 32-100ng/ml is considered normal, Vitamin D levels are optimal at 50-80 ng/ml. Vitamin D supplements are generally safe to take daily, though it may be best to have your levels checked before supplementation. Because Vitamin D is a fat-soluble vitamin, it is possible to take too much, which could theoretically lead to toxicity. In the meantime, getting outside daily for a few minutes of exposure to the sun may do much more than lift your mood, it may be one of the best preventative measures you can take.

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