Effects of vitamin D supplementation on diabetic foot ulcer healing: a meta-analysis

Purpose To systematically review the effect of vitamin D supplementation on diabetic foot ulcer (DFU) healing. Methods The PubMed, Web of Science, Science direct, Ebsco host, CNKI, WanFang, VIP, and CBM databases were electronically searched to collect randomized controlled trials (RCTs) on the impact of vitamin D supplementation on DFUs from inception to 19 November 2022. Two researchers independently screened the literature, extracted the data and assessed the risk of bias of the included studies. Meta-analysis was then performed by using RevMan 5.3 software. Results A total of seven studies involving 580 patients were included. The results of meta-analysis showed that compared with control group, the wound healing efficiency rate (RR = 1.42, 95%CI 1.03 to 1.95, P = 0.03) and wound reduction rate (MD = 13.11, 95%CI 4.65 to 21.56, P < 0.01) of the experimental group were higher; the change values of the wound area (MD = -3.29, 95%CI -4.89 to 1.70, P < 0.01) and 25 (OH) D (MD = 9.63, 95%CI 6.96 to 12.31, P < 0.01) were larger. Supplementation of vitamin D on DFU patients can improve glucose metabolism and insulin indexes: hemoglobin A1c (MD = -0.44, 95%CI -0.62 to -0.26, P < 0.01), fasting insulin (MD = -3.75, 95%CI -5.83 to -1.67, P < 0.01), HOMA - beta (MD = -5.14, 95%CI -8.74 to -1.54, P < 0.01), and quantitative insulin sensitivity check index (MD = 0.02, 95%CI 0.01 to 0.02, P < 0.01). It can also improve inflammation and oxidative stress markers: high sensitivity C-reactive protein (MD = -0.83, 95%CI -1.06 to -0.59, P < 0.01), erythrocyte sedimentation rate (MD = -15.74, 95%CI -21.78 to -9.71, P<0.01), nitric oxide (MD = 1.81, 95%CI 0.07 to 3.55, P = 0.04), and malondialdehyde (MD = -0.43, 95%CI -0.61 to -0.24, P<0.01). There was no statistically significant difference in changes of fasting plasma glucose, homeostasis model of assessment-insulin resistance, total antioxidant capacity, glutathione, very low density lipoprotein cholesterol, low density lipoprotein cholesterol, and high density lipoprotein cholesterol (P>0.05). Conclusion The current evidence suggests that vitamin D supplementation can significantly promote DFU healing by lowering blood sugar and alleviating inflammation and oxidative stress.