VOLUME 2 ISSUE 2    January 2007 VIEW ARCHIVE

Vitamin D: The Shining Flu-Fighter Are You Getting Enough? by Michelle Gibeault Traub, R.D. With flu season upon us, obtaining vaccination and practicing diligent hand-washing top the list of flu prevention recommendations.1 Good nutrition also remains important in maintaining a strong immune system to combat viruses. Studies now indicate that vitamin D, once only noted for its bone-building properties, may be a key nutritional component in enhancing immune function.   Vitamin D Really Shines A host of studies have recently concluded that vitamin D, the sunshine vitamin, plays a role in boosting the human immune system: During a flu outbreak in the hospital in which he worked, psychiatrist John. J. Cannell noticed that his patients did not get ill despite having contact with other sick patients. The possible explanation? All of Cannell's patients were receiving vitamin D supplements. Cannell's findings led him to review over 100 studies associating vitamin D with respiratory diseases. As a result, he and fellow researchers theorized that flu season occurs in winter months due to the lack of direct sunlight, and therefore, lower levels of protective D produced in the body.2, 3 A study in Science states that adding vitamin D to the blood of African-American subjects increased their ability to ward off Tuberculosis bacteria.2, 3  (See More Than Just Eye Color for more information on genetic risks) Findings from research conducted on girls living in Maine showed that 48 percent had low vitamin D levels at the end of the winter, while 17 percent had low levels at the end of summer likely due to the reduced sun exposure of that northern location.4  Sunscreen Blocks More Than Unwanted Rays Our bodies produce vitamin D through exposure to sunlight. As a result, getting enough vitamin D used to be as simple as spending time in the sun, largely ignoring the impact of dietary intake. However, skin cancer risks created a wide-spread effort to block out the sun's harmful rays. This effort, combined with everyday pollution and less direct sunlight during the winter months, has generally decreased the body's production of vitamin D.    The Vitamin D Challenge In addition to the evidence that sunlight is not effectively contributing to vitamin D production, most people are simply not getting enough D from their diets. The highest dietary sources of vitamin D - fish and milk - are not chosen favorites for many people. In addition, there is much speculation that the current dietary recommendations (Table 1) are much too low. According to Walter Willett, a Harvard researcher studying vitamin D's impact on cancer, "There's no one working in the field who thinks these levels still make sense." Researcher Anthony Norman of the University of California-Riverside agrees. When asked if vitamin D supplements should be recommended, Norman stated, "Unequivocally yes." 2     A Conservative Conclusion While research indicates that vitamin D may be a powerful immune booster, and that intakes are far from sufficient, toxicity is still a minor concern. Since vitamin D is fat-soluble, our bodies are able to store excess amounts. Too much can lead to nausea, vomiting, poor appetite, constipation, weakness, and weight loss.5 Given this factor, the Food and Nutrition Board of the Institute of Medicine has set a tolerable upper intake level based on age. For adults this level is currently 2000 IU (Table 2) which is rather difficult to exceed without consuming large amounts of fortified foods and supplements (milk, fish, fortified cereals or juices, etc.). Many physicians, including Meir Stampfer, M.D., Dr, P.H., believe that supplementation of 1000 IU per day is reasonable for most people.4    Vitamin D Resources   Table 1 Adequate Intake for vitamin D for infants, children, and adults*    Age Children Men Women Pregnancy Lactation Birth to 13 years 200 IU         14 to 18 years   200 IU 200 IU 200 IU 200 IU 19 to 50 years   200 IU 200 IU 200 IU 200 IU 51 to 70 years   400 IU 400 IU     71+ years   600 IU 600 IU     *Based on the Dietary Reference Intakes (DRIs) developed by the Institute of Medicine (IOM) of the National Academy of Sciences.  NOTE: many researchers now believe these levels are much too low.   Table 2 Tolerable Upper Intake Levels for vitamin D for infants, children, and adults * Age Men (μg/day) Women (μg/day) Pregnancy (μg/day) Lactation (μg/day) 0 to 12 months 1,000 IU 1,000 IU     1 to 13 years 2,000 IU 2,000 IU     14 to 18 years 2,000 IU 2,000 IU 2,000 IU 2,000 IU 19+ years 2,000 IU 2,000 IU 2,000 IU 2,000 IU * As determined by The Food and Nutrition Board of the Institute of Medicine   See also: Vitamin D: A Lifetime Achievement Award     References CDC, Preventing the Flu retrieved 1/2/07 http://www.cdc.gov/flu/protect/preventing.htm Kotz, Deborah. The ABCs of D, Almost everyone needs more of the sunshine vitamin. USNews.com posted 12/10/06, retrieved 1/2/07 LINK Raloff, Janet. The Antibiotic Vitamin: Deficiency in vitamin D may predispose people to infection. Week of Nov. 11, 2006; Vol. 170, No. 20 , p. 312, as retrieved 1/2/07 http://www.sciencenews.org/articles/20061111/bob9.asp Stampfer, Meir M, M.D, DR., P.H. Vitamin D in the Spotlight. Newsweek, http://www.msnbc.msn.com/id/15994150/site/newsweek/ retrieved 1/2/07 National Institutes of Health, Office of Dietary Supplements. Dietary Supplement Fact Sheet: Vitamin D. retrieved 1/4/07 LINK

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