Effect of Vitamin D Supplementation on the Incidence of Diabetes Mellitus.

Study answer

What this study found

Overall, vitamin D supplementation did not reduce incident type 2 diabetes mellitus when all populations and doses were pooled: 3,424 cases; RR 0.96 (95% CI, 0.90-1.03); P = 0.30; I2 = 3%. In post hoc subgroup analyses, moderate/high-dose vitamin D (≥1000 IU/day) was associated with lower diabetes incidence: 1,019 cases; RR 0.88 (95% CI, 0.79-0.99); P = 0.03; I2 = 0%, whereas lower-dose supplementation was not effective: RR 1.02 (95% CI, 0.94-1.10); P = 0.68; I2 = 0%. Benefit also appeared restricted to non-obese participants, with BMI <30 showing RR 0.68 (95% CI, 0.53-0.89) versus BMI ≥30…

Study & population

Systematic review and meta-analysis of randomized trials assessing vitamin D supplementation for prevention of type 2 diabetes mellitus.

Intervention

Vitamin D supplementation was evaluated across randomized trials using multiple formulations, including cholecalciferol (vitamin D3), ergocalciferol (vitamin D2), and an active analogue (eldecalcitol).

Key limitation

The pooled analysis showed no overall effect, and the apparent benefit came from post hoc subgroup analyses by dose, BMI, and prediabetes status.

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Original abstract