The effect of improved serum 25-hydroxyvitamin D status on glycemic control in diabetic patients: A meta-analysis

Abstract

Background: Type 2 diabetes is a global health concern, with an increased prevalence and high cost of treatment. Objective: The aim of this systematic review and meta-analysis was to determine the effect of vitamin Dsupplementation and improved vitamin Dstatus on glycemia and insulin resistance in type 2 diabetic patients. Data Source: We searched PUBMED/Medline, Cumulative Index to Nursing and Allied Health, and Cochrane Library (until January 2017). Study Selection: Prospective clinical trials were selected evaluating the impact of vitamin D supplementation on glycosylated hemoglobin (HbA1c), serum fasting plasma glucose (FPG), and homeostatic model assessment of insulin resistance (HOMA-IR) in diabetic patients. Data Extraction and Synthesis: We used a random-effects model to synthesize quantitative data, followed by a leave-one-out method for sensitivity analysis. The systematic review registration was CRD42017059555. From a total of 844 entries identified via literature search, 24 controlled trials (1528 individuals diagnosed with type 2 diabetes) were included. The meta-analysis indicated a significant reduction in HbA1c [mean difference: 20.30%; 95% confidence interval (CI): 20.45 to20.15, P,0.001], FPG [mean difference:24.9 mg/dL (20.27 mmol/L); 95% CI:28.1 to21.6 (20.45 to 20.09 mmol/L), P = 0.003], and HOMA-IR (mean difference: 20.66; 95% CI: 21.06 to 20.26, P = 0.001) following vitamin D supplementation and significant increase in serum 25-hydroxyvitamin D levels [overall increase of 17 6 2.4 ng/mL (42 6 6 nmol/L)]. Conclusions: Vitamin D supplementation, a minimum dose of 100 mg/d (4000 IU/d), may significantly reduce serum FPG, HbA1c, and HOMA-IR index, and helps to control glycemic response and improve insulin sensitivity in type 2 diabetic patients.