Women taking daily vitamin supplements containing vitamin D appear to be less likely to develop multiple sclerosis (MS), according to a new study.
MS is a disease in which the immune system attacks the fatty sheath of spinal cord neurons. Like wires missing their plastic insulation, the stripped neurons can't send electrical impulses efficiently. Researchers don't know what causes MS to develop, but geography may hold a clue; regions closer to the equator have a lower incidence of the disease than areas far north. This observation led scientists to postulate that vitamin D, made in the skin in the presence of sunlight, protects against MS. Other research suggests that vitamin D regulates some immune system activities, and recent experiments reveal that ample amounts of vitamin D can prevent mice from coming down with mouse MS.
To determine the relationship between vitamin D and the disorder, epidemiologist Kassandra Munger of the Harvard School of Public Health in Boston and colleagues examined health data from more than 187,000 women in the Nurses' Health Study. Of these women, 173 eventually developed MS. Comparing the amount of dietary supplements the women took, the researchers found that those who took supplements containing at least the USDA's recommended daily intake of vitamin D were 40% less likely to acquire the disease than women who didn't, the team reports in the 13 January issue of Neurology.
The study emphasizes the importance of adequate vitamin D intake in autoimmune disease, comments biochemist Hector DeLuca of the University of Wisconsin, Madison. But it's not the whole story as far as MS goes, notes neurophysiologist Stephen Reingold of the National Multiple Sclerosis Society in New York City. "Nothing in the paper says that vitamin D is the most important or only risk factor," he says. Other known risk factors include smoking and infection by the Epstein-Barr virus, the culprit behind mononucleosis.