Twenty four prospective controlled trials were included in this meta-analysis. A total of 1,500 patients with type 2 diabetes were analyzed. Authors found that 17 ng/mL incremental increase in vitamin D intake improved A1c by -0.30 %, fasting glucose by -5 mg/dL, and insulin resistance as measured by the HOMA-IR index.
It is important to screen, identify and supplement type 2 diabetes patients with vitamin D.
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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 D supplementation and improved vitamin D status 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: −0.30%, p < 0.001], FPG [mean difference: −4.9 mg/dL, p = 0.003], and HOMA-IR (mean difference: −0.66, p= 0.001) following vitamin D supplementation and significant increase in serum 25-hydroxyvitamin D levels [overall increase of 17 ng/mL]
Vitamin D supplementation, a minimum dose of 100 µg/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.