Effects of Vitamin D on Serum Lipid Profile in Patients with Type 2 Diabetes: A Meta-Analysis of Randomized Controlled Trials

Introduction: The effect of vitamin D on lipid profile in type 2 diabetic patients is controversial. This meta-analysis aimed to assess the effect of vitamin D on serum total cholesterol (TC), triglycerides (TG), low-density lipoproteins (LDL), and high-density lipoproteins (HDL) of these patients to elucidate the subject.Materials and Methods: Seven databases were searched and randomized controlled trials (RCTs) assessed the effect of vitamin D on lipid profile published until November 2015 were identified.Un- standardized mean difference and its corresponding 95% confidence interval (CI) was calculated from the effect sizes by using random effects model.Results: We found 2220 articles in our systematic search, after exclusion of un-related studies we enrolled 17 studies comparing intervention group (received vitamin D) with control group (received placebo) in the meta-analysis. Vitamin D significantly reduced serum TC (_3.74 mg/dl, 95% CI: _7.13 to _0.34, P = 0.031), but serum TG did not show significant reduction (_4.90 mg/dl, 95% CI: _15.11 to 5.31, P = 0.347). Results confirmed the significant lowering effect of vitamin D on LDL in patients with T2D (_2.55 mg/dl, 95% CI: _4.83 to _0.26, P = 0.029), but change in serum HDL was negligible (_0.72 mg/dl, 95% CI: _1.27 to _0.17, P = 0.010). Subgroup analyses showed that the baseline serum 25-hydroxy vitamin D of patients, vitamin D dosage, intervention duration, and the method of vitamin D application influence the effect of vitamin D on lipid markers.Conclusion: This study demonstrated that vitamin D improved serum levels of TC, TG, and LDL in patients with T2D but changes of serum HDL was not satisfactory.