Efficacy of vitamin D supplementation on glycemic control in type 2 diabetes patients: A meta-analysis of interventional studies

BACKGROUND: Conflicting evidence exists on the effect of vitamin D supplementation on glucose metabolism in subjects with type 2 diabetes (T2D). Therefore, this meta-analysis focuses on the relationship between vitamin D intervention and glycaemic control in subjects with T2D. METHODS: We reviewed available randomized controlled trials (RCTs) studies from the establishment time of each database to March 31, 2018. Stata 13.0 software was used to evaluate the included literature. RESULTS: Finally, a total of 19 RCT studies involving 747 intervention subjects and 627 placebo controls were included in this meta-analysis. Meta-analysis results showed that compared with the control group, the short-term vitamin D supplementation group had a decline in hemoglobin A1c (HbA1c), insulin resistance, and insulin. The Standard Mean Difference (SMD) (95% CI [95% confidence interval]) of HbA1c, insulin resistance, and insulin were −0.17 (−0.29, −0.05), −0.75 (−0.97, −0.53), −0.57 (−0.78, −0.35), respectively with all P value <.05. But there were no significant differences in long-term follow-up vitamin D intervention. CONCLUSION: Vitamin D supplementation in T2D patients can improve HbA1c, insulin resistance, and insulin in short-term intervention, suggesting that vitamin D can be considered as a therapeutic agent along with the other treatments for T2D.