Long-term data from two studies of female nurses suggest that use of vitamin D supplements, primarily in the form of multivitamins, may reduce the risk of multiple sclerosis (MS).
"It's exciting to think that something as simple as taking a multivitamin could reduce your risk of developing MS," said Dr. Kassandra Munger, from Harvard School of Public Health in Boston, who led the study.
As part of the 20-year Nurses' Health Study and the 10-year Nurses' Health Study II, a total of 187,563 women provided information on diet and multivitamin use at baseline and every 4 years thereafter. During follow up, 173 cases of MS were documented.
According to the report in the medical journal Neurology, women who used the most vitamin D were 41 percent less likely to develop MS than women who used none. This benefit held true even after adjusting for other factors such as patient age, smoking history, and birth location. Total vitamin D intake -- from foods and supplements -- also influenced MS risk. Women with the highest total intake were 33 percent less likely to develop MS than women with the lowest intake. In contrast, relying solely on food as the source of vitamin D didn't offer any protection against MS.
"Previous studies have provided support for a possible protective effect of vitamin D by showing that individuals with MS tend to have low vitamin D levels in blood and that sun exposure (which increases vitamin D levels) is associated with a lower risk of MS," Dr. Munger noted. "There is also evidence from studies on animals...that vitamin D can prevent (MS) development and slow its progression," she said.
Background: A protective effect of vitamin D on risk of multiple sclerosis (MS) has been proposed, but no prospective studies have addressed this hypothesis.
Methods: Dietary vitamin D intake was examined directly in relation to risk of MS in two large cohorts of women: the Nurses’ Health Study (NHS; 92,253 women followed from 1980 to 2000) and Nurses’ Health Study II (NHS II; 95,310 women followed from 1991 to 2001). Diet was assessed at baseline and updated every 4 years thereafter. During the follow-up, 173 cases of MS with onset of symptoms after baseline were confirmed.
Results: The pooled age-adjusted relative risk (RR) comparing women in the highest quintile of total vitamin D intake at baseline with those in the lowest was 0.67 (95% CI = 0.40 to 1.12; p for trend = 0.03). Intake of vitamin D from supplements was also inversely associated with risk of MS; the RR comparing women with intake of 400 IU/day with women with no supplemental vitamin D intake was 0.59 (95% CI = 0.38 to 0.91; p for trend = 0.006). No association was found between vitamin D from food and MS incidence.
Conclusion: These results support a protective effect of vitamin D intake on risk of developing MS.
K. L. Munger, S. M. Zhang, E. O’Reilly, M. A. Hernán, M. J. Olek, W. C. Willett, and A. Ascherio; Vitamin D intake and incidence of multiple sclerosis. Neurology 2004 Jan 62: 60-65.