K. L. Munger, MSc, S. M. Zhang, MD ScD, E. O’Reilly, MSc, M. A. Hernán, MD DrPH, M. J. Olek, DO, W. C. Willett, MD DrPH and A. Ascherio, MD DrPH
From the Departments of Nutrition (Drs. Willett and Ascherio, K.L. Munger and E. O’Reilly) and Epidemiology (Drs. Zhang, Hernán, Willett, and Ascherio), Harvard School of Public Health, and Division of Preventive Medicine (Dr. Zhang) and Channing Laboratory (Drs. Zhang, Willett, and Ascherio), Department of Medicine, Harvard Medical School and Brigham and Women’s Hospital, Boston, MA; and Multiple Sclerosis Center (Dr. Olek), Department of Neurology, University of California at Irvine.
Address correspondence and reprint requests to Ms. K.L. Munger, Department of Nutrition, Harvard School of Public Health, 665 Huntington Ave., Boston, MA 02115; e-mail: firstname.lastname@example.org
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.