Vitamin D intake and risks of systemic lupus erythematosus and rheumatoid arthritis in women.

Vitamin D has immune-modulating effects and may protect against the development of systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). We identified incident cases of SLE and RA among 186 389 women followed from 1980 to 2002 in the Nurses' Health Study and Nurses' Health Study II cohorts. We excluded subjects where SLE or RA was not confirmed by medical record review, and those who failed to return questionnaires. Semi-quantitative food frequency questionnaires assessed vitamin D intake from food and supplements. We used cumulative-updated total energy-adjusted dietary exposures for each 2-year cycle. Relationships between vitamin D intake and incident SLE and RA were examined in age-adjusted and Cox proportional hazards models, adjusted for confounders. Results were pooled using meta-analysis random effects models. We confirmed 190 incident cases of SLE and 722 of RA with dietary information. Increasing levels of vitamin D intake had no relationship to the relative risk of developing either SLE or RA. Vitamin D intake was not associated with risk of SLE or RA in these large prospective cohorts of women.