Serum and supplemental vitamin D levels and insulin resistance in T2DM populations: a meta-analysis and systematic review.
Level 1 - systematic review of randomized trials
Systematic review and meta-analysis of randomized controlled trials and observational studies
PubMed 37524765 · doi:10.1038/s41598-023-39469-9
What was done
Four databases (PubMed, Embase, Cochrane Library, and Web of Science) were searched through July 2022 for randomized controlled trials (RCTs) and observational studies assessing serum or supplemental vitamin D and insulin resistance in type 2 diabetes mellitus populations. Continuous outcomes were pooled as standardized mean differences (SMDs) using random-effects meta-analysis, and correlation coefficients were normalized via Fisher's z-transformation.
What was found
The meta-analysis included 18 RCTs (1,243 participants) and 20 observational studies (11,063 participants). Compared to routine treatment, vitamin D supplementation significantly lowered: - Serum insulin: SMD = -0.265 (95% CI: -0.394 to -0.136, P < 0.05) - Glucose: SMD = -0.170 (95% CI: -0.301 to -0.039, P < 0.05) - HOMA-IR: SMD = -0.441 (95% CI: -0.582 to -0.300, P < 0.05) In observational studies, serum vitamin D showed weak but statistically significant negative correlations with insulin (r = -0.08, 95% CI: -0.12 to -0.04), glucose (r = -0.06, 95% CI: -0.11 to -0.01), and HOMA-IR (r = -0.08, 95% CI: -0.09 to -0.06).
Why it matters
This review provides quantitative evidence that vitamin D supplementation modestly improves glycemic control and insulin sensitivity in individuals with type 2 diabetes.
Limits
The abstract does not report vitamin D dosages, treatment durations, baseline vitamin D status, or statistical heterogeneity metrics. Observed observational correlation coefficients were very weak (|r| <= 0.08), and clinical relevance of the effect sizes cannot be fully determined from the abstract alone.
Cited by
- supports Low vitamin D levels cause or worsen insulin resistance.