What is the impact of vitamin D supplementation on glycemic control in people with type-2 diabetes: a systematic review and meta-analysis of randomized controlled trails

Study answer

What this study found

Vitamin D supplementation was associated with modest improvements in glycemic control in people with type 2 diabetes, particularly when baseline vitamin D status was deficient. Pooled effects showed reductions in fasting plasma glucose (WMD -5.02 mg/dl; 95% CI -6.75 to -3.28), HbA1c (WMD -0.20%; 95% CI -0.29 to -0.11), and HOMA-IR (WMD -0.42; 95% CI -0.76 to -0.07). The strongest effects appeared in deficient participants and in higher-dose, shorter-duration regimens. However, heterogeneity was substantial for key outcomes, with I2 = 98.2% for both fasting plasma glucose and HbA1c, so the…

Study & population

Systematic review and meta-analysis of 46 randomized controlled trials in adults with type 2 diabetes.

Intervention

Vitamin D supplementation was evaluated across 46 randomized controlled trials using diverse oral and intramuscular regimens, including daily doses of 20 to 6,000 IU, weekly doses such as 30,000 to 60,000 IU, and intermittent bolus doses such as 50,000 to 400,000 IU.

Key limitation

Considerable between-study heterogeneity, varied dosing schedules and routes, and differences in baseline vitamin D status limit confidence in the pooled estimates.

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Original abstract