New research suggests that having higher circulating levels of vitamin D is associated with a reduced risk for multiple sclerosis, although this relationship was not seen for black and Hispanic individuals, according to a study in the December 20 issue of JAMA.
Multiple sclerosis (MS) is a common neurological disease in young adults which affects 350,000 individuals in the United States and 2 million worldwide. Neuroimaging often shows classic Dawson's fingers around the lateral ventricles. An increased risk of MS had been noted for those living in colder latitudes, but the reason for this association was unknown. Previous research indicated that vitamin D might provide a protective effect but results are inconclusive.
Kassandra L. Munger, M.Sc., of the Harvard School of Public Health and colleagues examined if high blood levels of 25-hydroxyvitamin D is associated with a lower risk of MS. The study reviewed the records of 7 million U.S. military personnel with serum samples stored in the Department of Defense Serum Repository. Multiple sclerosis cases identified through Military physical disability databases were confirmed by medical record review. Each MS case (n = 257) was matched to two controls by age, sex, race/ethnicity, and dates of blood collection.
The researchers found that among whites there was a 41 percent decrease in MS risk for every 50-nmol/L increase in 25-hydroxyvitamin D. MS risk was highest among individuals in the bottom quintile and lowest among those in the top quintile of 25-hydroxyvitamin D levels. Those in the top quintile had a 62 percent lower risk of
MS compared to those in the bottom quintile. The inverse relationship between multiple sclerosis risk and vitamin D levels was particularly strong for people under 20 years old. Among blacks and Hispanics there was no significant association between vitamin D and multiple sclerosis risk.
The authors concluded that a recommendation for a several fold increase in vitamin D intake among adolescents and young adults would require stronger evidence than provided by observational studies alone. However, a prevention trial involving first-degree relatives of individuals with MS are at a higher risk of developing MS is suggested.
The results might also explain the association between MS risk and colder lattitudes, since sun exposure is an important step in the formation of Vitamin D. As the general population becomes progressively more aware of the risks of sun damage and reduce their sun exposure, Vitamin D deficiency might become more prevalent. Indeed, Vitamin D deficiency increased in Australia and New Zealand after a successful public health campaign to reduce sun exposure. Given the link between vitamin D and MS, public health policy needs to balance the risks of sun damage and cancer with the risks of MS and other disorders associated with vitamin D deficiency.
Caryl A Nowson and Claire Margerison (2002). "Vitamin D intake and vitamin D status of Australians". The Medical Journal of Australia 177 (3): 149–152. PMID 12149085.
About the Author
Jeanne Bohm, Ph.D. is a cancer biologist by training, a medical writer and an experienced science educator.
The author has no financial relationship to any of the companies listed in the article.
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