# Assessing the potency of vitamin D augmentation on saccharometric indices in type 2 diabetes: a meta-analysis

## TL;DR

This study finds that vitamin D supplements raise blood vitamin D levels in type 2 diabetes patients but do not improve blood sugar control or insulin sensitivity.

## Contribution

The study is the first meta-analysis to systematically evaluate vitamin D's impact on multiple glycemic indices in type 2 diabetes.

## Key findings

- Vitamin D supplementation significantly increased serum 25(OH)D levels in T2D patients.
- No significant improvements in HbA1c or HOMA-IR were observed with vitamin D supplementation.
- Vitamin D showed a favorable safety profile with no significant increase in adverse events.

## Abstract

This meta-analytical investigation sought to elucidate the therapeutic efficacy and tolerability of vitamin D supplementation in modulating glycemic indices among individuals diagnosed with type 2 diabetes (T2D).

Systematic searches were performed across PubMed, Embase, Web of Science, Cochrane Library, and Chinese databases (CNKI and Wanfang) to identify relevant randomized controlled trials (RCTs). Studies were deemed eligible if they enrolled adult T2D populations, administered vitamin D interventions, and reported outcomes including glycated hemoglobin (HbA1c), homeostasis model assessment of insulin resistance (HOMA-IR), or serum 25-hydroxyvitamin D [25(OH)D] concentrations.

Ten RCTs, encompassing a total of 3,460 participants, met inclusion criteria. Intervention durations varied between 3 and 12 months, and dosing regimens ranged from 500 IU and 60,000 IU. Pooled analysis revealed a significant increase in serum 25(OH)D levels following supplementation (SMD: 4.01; 95% CI: 2.43 to 5.59; p < 0.001; I2 = 99.3%). In contrast, no statistically significant improvements were observed in HbA1c (SMD: 0.08; 95% CI: −0.25 to 0.37; p < 0.001; I2 = 86.5%) or HOMA-IR (SMD: 5.95; 95% CI: −2.87 to 14.77; p < 0.001; I2 = 100.0%). Adverse event profiles were similar between the vitamin D and control groups (RR: 1.19; 95% CI: 0.79 to 1.80; p = 0.183; I2 = 43.5%).

Vitamin D supplementation yield a consistent rise in serum 25(OH)D concentrations but exerts no discernible effect on glycemic regulation or insulin sensitivity in T2D populations. The favorable safety profile supports its tolerability. Considerable heterogeneity in metabolic outcomes underscores the need for future investigations stratified by baseline vitamin D status, enhancement regimen, and study duration.