January 12, 2004
Laurie Barclay, MD
Vitamin D supplements may protect against developing multiple sclerosis (MS), according to an analysis of data from the Nurse's Health Study published in the Jan. 13 issue of Neurology.
"Because the number of cases of MS increases the farther you get from the equator, one hypothesis has been that sunlight exposure and high levels of vitamin D may reduce the risk of MS," lead author Kassandra L. Munger, MSc, from Harvard School of Public Health in Boston, Massachusetts, says in a news release. "This is the first prospective study to look at this question. These results need to be confirmed with additional research, but it's exciting to think that something as simple as taking a multivitamin could reduce your risk of developing MS."
Earlier research suggesting that vitamin D may play a role in MS development includes mouse models of experimental autoimmune encephalomyelitis, and clinical studies linking MS to insufficient levels of vitamin D. Periods of low vitamin D levels may precede exacerbations, and high vitamin D levels may precede remissions.
Upon enrollment in the 20-year Nurses' Health Study or the 10-year Nurses' Health Study II and every four years thereafter, women without MS symptoms before enrollment completed questionnaires on diet and use of multivitamin supplements. Of 187,563 women, 173 women developed MS during the study.
Women ingesting 400 IU or more of vitamin D per day from supplements were 40% less likely to develop MS than those who used no supplements (relative risk [RR], 0.59; 95% confidence interval [CI], 0.38 - 0.91; P for trend = .006). Compared with women in the lowest quintile of total vitamin D intake, women in the highest quintile had 33% lower risk of developing MS (RR, 0.67; 95% CI, 0.40 - 1.12; P for trend = .03).
High intake of vitamin D from supplements only or from both supplements and food appeared to protect against developing MS, but high intake of vitamin D from food only did not. Adjustment for smoking and latitude at birth did not affect these findings.
Study limitations include multivitamins being the primary source of supplemental vitamin D intake, making it difficult to exclude the effect of other vitamins.
"However, none of these vitamins was itself significantly associated with risk of MS after adjusting for total vitamin D intake or vitamin D from supplements," Ms. Munger says, adding that future prospective studies should measure the levels of vitamin D in the blood before MS onset.
The National Institutes of Health supported this study.
Reviewed by Gary D. Vogin, MD
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