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Review
. 2025 Jul 30;17(15):2489.
doi: 10.3390/nu17152489.

The Impact of Vitamin D Supplementation on Fasting Plasma Glucose, Insulin Sensitivity, and Inflammation in Type 2 Diabetes Mellitus: A Systematic Review and Meta-Analysis

Enny Probosari  1   2 , Hertanto W Subagio  2 , Heri-Nugroho  3 , Banundari Rachmawati  4 , Siti F Muis  2 , Kevin C Tjandra  5 , Dwi Adiningsih  6 , Tri I Winarni  7   8
Affiliations
Review

The Impact of Vitamin D Supplementation on Fasting Plasma Glucose, Insulin Sensitivity, and Inflammation in Type 2 Diabetes Mellitus: A Systematic Review and Meta-Analysis

Enny Probosari et al. Nutrients. .

Abstract

Background/Objectives: Vitamin D supplementation has shown promise in managing type 2 diabetes mellitus (T2DM), while the simultaneous impact on glycemic control and inflammation in T2DM remains poorly understood. This study aimed to investigate the potential role of vitamin D supplementation in managing T2DM using fasting plasma glucose (FPG), insulin levels, HOMA-IR, HOMA-B, HbA1c, and Hs-CRP as the biomarkers. Methods: Original articles from Scopus, Pubmed, Cochrane Library, Epistemonikos, and ScienceDirect published between 2014 and 2024 were the sources. Inclusion criteria included studies conducted as clinical trials or randomized controlled trials involving adult patients diagnosed with T2DM undergoing treatment with vitamin D. The risk of bias was evaluated using the ROB-2 tool and meta-analysis was conducted to quantitatively synthesize the results across the studies using pooled effect sizes and confidence intervals. Results: Nine studies were included in the meta-analysis. Significant differences were found at 12-week follow-up in insulin level (MD(-3.59) [95% CI: -6.93, -0.25]), HOMA-B (MD(-50.35) [95% CI: -92.29, -8.41]), hs-CRP (-2.51 [95% CI: -3.45, -1.57]), and HbA1c level (MD(-0.30) [95% CI: -0.54, -0.06]) and at 24-week follow-up in HOMA-IR (MD(-0.38) [CI: -0.53, -0.24]). The quality of the included studies was generally moderate, with three showing a potential risk of bias. Conclusions: The observed trends in FPG, insulin levels, HOMA-IR, HOMA-B, HbA1c, and hs-CRP indicate that vitamin D may influence glycemic control, insulin sensitivity, and inflammation, but these effects are often modest and may diminish over time. Future studies should explore longer duration randomized trials with standardized dosing and baseline vitamin D status stratification.

Keywords: biomarkers; fasting plasma glucose; hs-CRP; insulin sensitivity; type 2 diabetes mellitus; vitamin D.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
Flow diagram for PRISMA 2020.
Figure 2
Figure 2
Forest plot for the FPG outcome. All studies shown are referenced as: Asemi Z., et al., (2016), Cojic M., et al., (2021), Mousa A., et al., (2017), Sun X., et al., (2023), Bhatt SP., et al., (2020), Krul-Poel Y., et al., (2015), Muñoz-Aguirre P., et al., (2014) [26,28,29,30,31,32,33].
Figure 3
Figure 3
Forest plot for insulin level outcome. All studies shown are referenced as: Asemi Z., et al., (2016), Cojic M., et al., (2021), Jafari T., et al., (2015), Mousa A., et al., (2017), Sun X., et al., (2023), Bhatt SP., et al., (2020), Krul-Poel Y., et al., (2015), Muñoz-Aguirre P., et al., (2014) [26,27,28,29,30,31,32,33].
Figure 4
Figure 4
Forest plot for HOMA-IR outcome. All studies shown are referenced as: Asemi Z., et al., (2016), Cojic M., et al., (2021), Jafari T., et al., (2015), Sun X., et al., (2023), Bhatt SP., et al., (2020), Hajj CE., et al., (2020), Krul-Poel Y., et al., (2015), Muñoz-Aguirre P., et al., (2014) [20,26,27,28,29,31,32,33].
Figure 5
Figure 5
Forest plot for HOMA-B outcome. All studies shown are referenced as: Asemi Z., et al., (2016), Jafari T., et al., (2015), Krul-Poel Y., et al., (2015) [27,28,29].
Figure 6
Figure 6
Forest plot for HbA1C outcome. All studies shown are referenced as: Cojic M., et al., (2021), Sun X., et al., (2023), Hajj CE., et al., (2020), Krul-Poel Y., et al., (2015), Muñoz-Aguirre P., et al., (2014) [20,26,28,32,33].
Figure 7
Figure 7
Forest plot for Hs-CRP outcome. All studies shown are referenced as: Asemi Z., et al., (2016), Jafari T., et al., (2015), Hajj CE., et al., (2020) [20,27,29].
Figure 8
Figure 8
Forest plot for the mean difference from baseline of serum vitamin D. All studies shown are referenced as: Cojic M., et al., (2021), Hajj CE., et al., (2020), Jafari T., et al., (2015), Krul-Poel Y., et al., (2015), Mousa A., et al., (2017) [20,27,28,30,32].
Figure 9
Figure 9
Baujat plot for fasting plasma glucose outcome.
Figure 10
Figure 10
Baujat plot for insulin level outcome.
Figure 11
Figure 11
Baujat plot for HOMA-IR outcome.
Figure 12
Figure 12
Baujat plot for HOMA-B outcome.
Figure 13
Figure 13
Baujat plot for HbA1c level outcome.
Figure 14
Figure 14
Baujat plot for hs-CRP level outcome.
Figure 15
Figure 15
Baujat plot for level change in serum Vitamin D from Baseline outcome.
See this image and copyright information in PMC

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