Dietary intake of vitamin D during adolescence and risk of multiple sclerosis.

Adolescence may be an important etiological period in the development of multiple sclerosis (MS), and studies suggest that adequate vitamin D nutrition is protective. Here, the authors examined whether dietary intake of vitamin D during adolescence decreases the risk of MS in adulthood. In 1986 in the Nurses' Health Study and in 1998 in the Nurses' Health Study II (NHSII), women completed a food frequency questionnaire regarding their dietary intake during adolescence. From this, daily intake of vitamin D was calculated. Adolescent diet was available for 379 incident MS cases confirmed over the combined 44 years of follow-up in both cohorts, and for 67 prevalent cases in the NHSII who had MS at baseline (1989). Cox proportional hazards models were used to calculate relative risk estimates and 95% confidence intervals. Total vitamin D intake during adolescence was not associated with MS risk. Intake of ≥ 400 IU/day of vitamin D from multivitamins was associated with a non-statistically significant reduced risk (RR compared to no intake = 0.73, 95% CI: 0.50-1.07, P = 0.11), whereas intake of whole milk, an important source of dietary vitamin D, was associated with an increased risk. The possibility of opposite effects of vitamin D and milk intake on MS risk should be considered in future studies.