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

Abstract

Background There is conflicting evidence on the effect of vitamin D on glycemic control. Therefore, in the current meta-analyses, we aimed to assess the effect of vitamin D supplementation on the glycemic control of type 2 diabetes (T2D) patients. Methods We conducted a comprehensive search in electronic databases including; PubMed/Medline, Web of Science, Scopus, Embase, Cochrane Central Register of Controlled Trials (CENTRAL), and NIH’s Clinical Trials Registry, from the inception of each database up to January first, 2021. Results A total of 46 randomized controlled trials (RCTs) consisting of 2164 intervention subjects and 2149 placebo controls were included in this meta-analysis. Pooled analyses for HbA1c showed a significant change between the intervention and placebo group, the weighted mean difference (WMD)(95% confidence interval(CI)) was -0.20%(-0.29, -0.11) with P < 0.001. Analyses for assessing changes in FPG found a significant reduction in the intervention group after vitamin D supplementation, the WMD (95%CI) was -5.02 mg/dl (-6.75,-3.28) with P < 0.001. The result of pooled analyses for HOMA-IR revealed a significant change between the intervention and control group, the WMD (95%CI) was -0.42(-0.76, -0.07) with P = 0.019. The subgroup analyses showed the most efficacy in a higher dose and short intervention period and in subjects with deficient vitamin D status. Conclusion Vitamin D supplementation might be beneficial for the reduction of FPG, HbA1c, and HOMA-IR in type 2 diabetes patients with deficient vitamin D status. This effect was especially prominent when vitamin D was given in large doses and for a short period of time albeit with substantial heterogeneity between studies and a probability of publication bias.

Vitamin D for glycemic control following an acute pulmonary exacerbation: A secondary analysis of a multicenter, double-blind, randomized, placebo-controlled trial in adults with cystic fibrosis

“…al. found that vitamin D supplementation was associated with reduced HbA1c when participants were vitamin D deficient at baseline [66]. Thus, prior findings have indicated conflicting results regarding the therapeutic effects of vitamin D on glycemic control, especially regarding optimal dosage and duration.…”

Vitamin D—A New Therapeutic Target in the Management of Type 2 Diabetes Patients

“…Vitamin D deficiency is also correlated with other factors, such as DM duration, iron concentration, and renal function assessed by eGFR. A recent systematic review and meta-analysis of 46 randomized clinical trials showed that vitamin D supplementation reduced the HbA1c up to 0.2%, the beneficial effect on glycemic control being more intense in T2DM patients with 25(OH)D deficiency [ 48 ]. The relationship between age and lower values of vitamin D may be explained by the reduced mobility of the elderly and, therefore, their inability to be exposed to the sun.…”

Vitamin D Alleviates Type 2 Diabetes Mellitus by Mitigating Oxidative Stress-Induced Pancreatic β-Cell Impairment

“…Previous clinical and basic studies indicated that vitamin D might exert beneficial effects on the symptoms or the prevention of T2DM [14,16,17,32]. Furthermore, a latest metaanalysis suggested the beneficial effects of vitamin D on the con- trol of blood glucose in patients with T2DM and the prevention of diabetic complications [33]. However, the application of vitamin D in the prevention and treatment of T2DM remains controversial and the understanding of the anti-T2DM mechanisms of vitamin D is still lacking.…”