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Vitamin D May Prevent MS

Dosage Found in Multivitamins Reduces Risk by 40%
WebMD Health News

Jan. 12, 2004 -- Evidence continues to mount showing that a little vitamin D can do a lot of good. The latest: A new study indicating that women who get doses typically found in daily multivitamin supplements -- of at least 400 international units -- are 40% less likely to develop multiple sclerosis compared with those not taking over-the-counter supplements.

This finding, by a team of Harvard researchers and published in this week's issue of Neurology, comes just a few days after another study links vitamin D deficiency with an increased risk of rheumatoid arthritis. Like MS, rheumatoid arthritis is an autoimmune disorder, a classification for some 80 different ailments in which the immune system mistakenly attacks healthy tissue and organs in the body.

"We've known for some time that vitamin D can affect function of the immune system, which could explain why it seems beneficial to both of these autoimmune conditions," says Kassandra Munger, MSc, of Harvard School of Public Health, a researcher for this study. "In animal studies, vitamin D been shown to suppress the autoimmune response in rats with a disorder very similar to MS."

Other recent studies link vitamin D deficiency to a greater risk of other ailments, including heart disease, diabetes, unexplained muscle and joint pain, and various forms of cancer. As with MS and other autoimmune diseases, the secret may be in how this nutrient affects cell activity.

"We need adequate amounts of vitamin D to keep cell growth and activity in check," says Michael Holick, MD, PhD, director of the Vitamin D Research Lab at Boston University Medical Center and considered by many to be the nation's leading authority on this vitamin. When the body is deficient in this crucial nutrient -- best known for coming from sunlight -- cells can go haywire, become overly active or multiplying too quickly.

That's why the new finding doesn't surprise Holick, who wasn't involved in it. "It's been well-known that if you live at a higher latitude, where there's less sun exposure, you're at a higher risk of developing MS," he tells WebMD. Conversely, if you live in a sunny climate where vitamin D can easily be absorbed year-round from sunlight for your first 10 years, "it imprints on you a decreased MS risk that can last a lifetime," Holick explains.

Munger's results are encouraging because 20% to 80% of Americans may already be vitamin D deficient -- at least during winter months. While as little as 10 minutes of sun exposure on bare, unprotected skin can prevent deficiencies in warm and sunny months, it's virtually impossible for most Americans to get that kind of exposure this time of year.

Good food sources of vitamin D include:

  • Fortified milk, 8 ounces contain approximately 100 IU of vitamin D
  • Cod liver oil, 1 tablespoon contains approximately 1300 IU of vitamin D
  • Cold-water fish such as salmon and herring, 3 ounces contain approximately 400 to 750 IU of vitamin D respectively.

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