Effect of Vitamin D Supplementation on Vascular Function and Inflammation in Patients with Chronic Kidney Disease: A Controversial Issue

Vitamin D deficiency is common in patients with CKD and is associated with vascular dysfunction and inflammation. In recent years, some randomized controlled trials have revealed the effect of vitamin D supplementation on vascular function and inflammation in CKD patients, but the results are inconsistent. Thus, in light of the controversy, we performed a systematic review and meta-analysis of the effect of vitamin D in patients with CKD. We searched the literature in multiple databases for clinical trials from the date of inception to December 2018. The standardized mean difference (SMD) effect size was pooled using fixed and random effects models. A total of 10 randomized controlled trials involving 579 patients were included in the meta-analysis; among these, 313 patients were treated with vitamin D, and the control group included 266 who received a placebo. This meta-analysis revealed no statistical significance in the levels of flow-mediated dilatation (SMD, 0.94; 95% CI, -0.33 to 2.21; P = 0.15); pulse wave velocity (SMD, -0.13; 95% CI, -0.38 to 0.13; P = 0.33); systolic BP (SMD, -0.04; 95% CI, -0.29 to 0.22; P = 0.77); diastolic BP (SMD, 0.01; 95% CI, -0.26 to 0.27; P = 0.97); and CRP (SMD, -0.09; 95% CI, -0.44 to 0.26; P = 0.61) between the vitamin D group and controls for patients with CKD. Short-term intervention with vitamin D was not associated with improvements in vascular function and inflammation, as measured by flow-mediated dilatation, pulse wave velocity, systolic BP, diastolic BP and CRP. This suggested that there is insufficient evidence to conclude the benefit of vitamin D supplementation on vascular function and inflammation in CKD patients.