View article

Background: Individual randomized clinical trials have not shown conclusively that taking vitamin D can prevent type 2 diabetes.

Methods: We conducted a systematic review and meta-analysis of individual participant-level data to determine whether vitamin D supplementation lowers the risk of diabetes in people with prediabetes. Trials published through February 12, 2021, that compared oral vitamin D supplementation (alone) with placebo over a minimum 2-year follow up, and had new-onset diabetes as a primary outcome were included. Proportional hazards models were used to analyze individual participant data, with pre-specified intention-to-treat (ITT) and per-protocol analyses, without and after adjustment for baseline age, gender, BMI, race and hemoglobin A1c. Safety was also assessed.

Results: Three trials were eligible (testing D 3 20,000 IU/week [Tromsø], D 3 4,000 IU/day [D2d], and eldecalcitol 0.75 …