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Vitamin D for Flu Prevention

Back in 1981, in the "Journal of Hygiene," a general practitioner named Edgar Hope-Simpson proposed the hypothesis that, based on studies of flu outbreaks throughout the world, there is a "seasonal stimulus" which must be associated with these infections. In the December 2006 issue of "Epidemiology and Infection," they published a review that concludes that the seasonal stimulus that Hope-Simpson was looking for is vitamin D.

  1. The Evidence for Vitamin D

    • The conclusion that vitamin D, or lack of it, is a seasonal stimulus for flu outbreaks is based on the evidence that radiation from the sun stimulates extreme vitamin D production in the body. Vitamin D stimulates the work of killer cells and anti-microbial peptides. These peptides, according to JJ Cannell, who authored the review in "Epidemiology and Infection," live in the cells that line the respiratory tract and protect the lungs from infections. When sunlight, and therefore sun exposure, is at its weakest point, which is the winter months, that is when outbreaks of the flu are seen. Other facts that lead to this conclusion are that respiratory infections are often seen in those who are vitamin D deficient; treatment with cod liver oil, loaded with vitamin D, reduces the incidences of respiratory infections, as does exposure to UV light, whether natural or artificial.

    Putting It All Together

    • Taking this information and putting it to use is a great way to protect yourself during flu season. Since during the winter months you are not able to produce enough natural vitamin D, due to lack of adequate sun exposure, your best defense is to supplement it in your diet. The vitamin D that is produced in the skin by the sun is called vitamin D3, or cholecalciferol. This is also the vitamin D that is naturally found in some food sources, although these sources are very few. Salmon, tuna and mackerel contain D3, as does cod liver oil. There are other food sources that are fortified with vitamin D, which means it is added to the product, and these include milk and dairy products, as well as some juices.

    Choosing the Right Supplements

    • It is difficult to obtain the necessary amounts of vitamin D through food sources only, so supplementation is very important. According to the National Institutes of Health Office of Dietary Supplements, there are 2 forms of vitamin D. D3, or cholecalciferol, as mentioned above, and D2, also known as ergocalciferol. The NIH reports that vitamin D3 and D2 are metabolized in different ways, and that D3 appears to be more effective in raising the amount of vitamin D in the body and keeping those levels raised for a longer period of time, offering you more protection against the flu. When shopping for a supplement, check the label to be sure that the vitamin D is in the form of D3, cholecalciferol. To prevent the flu, Dr. John Pan, from George Washington University Medical Center, and Women's Day Magazine Health Advisor, suggests taking a daily supplement of 1,000 to 2,000mg. However, if you find yourself coming down with flu symptoms, Dr. Pan states that you should take 1,000 mg per pound of body weight, but do not take this high dose for longer than 3 days. As with any supplements, consult your doctor before taking them, especially if you are on any medication.

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