The planning committee relied on observational longitudinal data and relevant intervention studies to estimate a plausible hazard ratio. In two metaanalyses that combined data from cohort studies, the pooled relative risk of type 2 diabetes comparing the highest with the lowest quartile of 25OHD concentration was 0.59 (95% CI 0.52–0.67) (31) and 0.62 (95% CI 0.54–0.70) (7), with little heterogeneity between studies. In a short-term trial, the 2,000 IU/day vitamin D3 supplementation, which raised blood 25OHD concentration to 31 ng/mL, improved measures of b-cell function (disposition index) by ;40% and glycemia (hemoglobin A1c) by ;50% after 4 months (11). After taking into consideration all published data and