Women who take vitamin D supplements through multivitamins are 40% less likely to develop multiple sclerosis (MS) than women who do not take supplements, according to a new study. Food is a source of vitamin D, and the body makes vitamin D through exposure to sunlight.

“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,” said study author Kassandra Munger, MSc, of Harvard School of Public Health in Boston. “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.”

The researchers examined data from two large studies involving women, the 20-year Nurses’ Health Study and the 10-year Nurses’ Health Study II. The women’s diets and use of multivitamin supplements were assessed as the studies began and then again every four years. There were 187,563 women in the study. Of those, 173 women developed MS during the course of the study. Those with the highest intake of vitamin D from supplements (400 IU or more per day) were 40% less likely to develop MS than those who used no supplements.

Earlier research also points to the role of vitamin D in MS. Studies with mice have shown that vitamin D supplements can prevent or favourably affect the course of the disease. Other studies have shown that people with MS tend to have insufficient levels of vitamin D, and that periods of low vitamin D occur before times of high disease activity.

American Academy of Neurology, Jan 12, 2004