Plasma 25-Hydroxyvitamin D Concentration and Risk of Incident Type 2 Diabetes in Women

OBJECTIVE To determine the association between 25-hydroxyvitamin D (25-OHD) concentration and risk of incident type 2 diabetes. RESEARCH DESIGN AND METHODS In a nested case-control study conducted among 608 women with newly diagnosed type 2 diabetes and 559 control subjects in the Nurses' Health Study, we measured the association between baseline plasma 25-OHD concentration and risk of incident diabetes. RESULTS After adjusting for matching factors and diabetes risk factors, including BMI, higher levels of plasma 25-OHD were associated with a lower risk for type 2 diabetes. The odds ratio for incident type 2 diabetes in the top (median 25-OHD, 33.4 ng/ml) versus the bottom (median 25-OHD, 14.4 ng/ml) quartile was 0.52 (95% CI 0.33-0.83). The associations were consistent across subgroups of baseline BMI, age, and calcium intake. CONCLUSIONS Plasma 25-OHD concentration was associated with lower risk of incident type 2 diabetes in women.