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. 2018 May 25;2(7):687-709.
doi: 10.1210/js.2017-00472. eCollection 2018 Jul 1.

Vitamin D Supplementation, Glycemic Control, and Insulin Resistance in Prediabetics: A Meta-Analysis

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Free PMC article

Vitamin D Supplementation, Glycemic Control, and Insulin Resistance in Prediabetics: A Meta-Analysis

Naghmeh Mirhosseini et al. J Endocr Soc. .
Free PMC article

Abstract

Diabetes prevention is a public health priority. Vitamin D supplementation may help prevent the development of diabetes in persons at increased risk. We performed a meta-analysis of controlled clinical trials that assessed glycemic outcome measures among adults at risk for type 2 diabetes, including prediabetes, overweight, or obesity. We searched PUBMED/ MEDLINE, CINAHL, and Google Scholar databases for trials published prior to April 2017. Placebo-controlled clinical trials with random allocation to vitamin D with or without calcium supplementation were selected. Data collection included country, study design, inclusion criteria, sample size, form, and dose of vitamin D, supplementation interval, control group, duration, participant characteristics, comorbidities, baseline and follow-up serum 25-hydroxyvitamin D [25(OH)D] concentration, and available outcome measures [glycosylated hemoglobin (HbA1c), fasting plasma glucose, plasma glucose after 2-hour oral glucose tolerance test, and homeostatic model assessment of insulin resistance (HOMA-IR)]. Data synthesis was conducted using random-effect models (PROSPERO registration no. CRD42017055326). Twenty-eight trials, representing 3848 participants, met the eligibility criteria. Compared with the control group, vitamin D supplementation significantly reduced HbA1c level by -0.48% (95% CI, -0.79 to -0.18), fasting plasma glucose level by -0.46 mmol/L (95% CI, -0.74 to -0.19), and HOMA-IR level by -0.39 (95% CI, -0.68 to -0.11). Subgroup analysis revealed that the effects of vitamin D supplementation on different glycemic measures were influenced by age, calcium coadministration, vitamin D deficiency, serum 25(OH)D level after supplementation, and duration of supplementation. Vitamin D supplementation and improved vitamin D status improved glycemic measures and insulin sensitivity and may be useful as part of a preventive strategy for type 2 diabetes.

Keywords: 25-hydroxyvitamin D; cholecalciferol; diabetes; hemoglobin A1c; prediabetes; vitamin D.

Figures

Figure 1.
Figure 1.
Study selection flow diagram. PRISMA flow diagram of search results following study section procedure assessing vitamin D supplementation and glycemic control among RCTs of adult population.
Figure 2.
Figure 2.
Forest plot of mean change from baseline in serum 25(OH)D concentrations (nmol/L) between vitamin D supplementation and control.
Figure 3.
Figure 3.
Forest plot of mean change from baseline in HbA1c (%) between vitamin D supplementation and control.
Figure 4.
Figure 4.
Forest plot of mean change from baseline in FPG (mmol/L) between vitamin D supplementation and control.
Figure 5.
Figure 5.
Forest plot of mean change from baseline in HOMA-IR between vitamin D supplementation and control.
Figure 6.
Figure 6.
Forest plot of mean change from baseline in plasma glucose after 2HPG (mmol/L) between vitamin D supplementation and control.
Figure 7.
Figure 7.
(a) Funnel plot of SE by standardized mean difference for HbA1c, detailing publication bias in the studies selected for analyses. Closed circles represent observed published studies. (b) “Trim and fill” method to impute for potentially missing studies for HbA1c. Four potentially missing studies were imputed in funnel plot. Closed circles represent observed published studies. Squares with circle inside represent imputed studies.

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