Effects of vitamin D on inflammatory state in patients with chronic kidney disease: A controversial issue

Abstract Background The anti‐inflammatory effect of vitamin D in patients with chronic kidney disease (CKD) remains controversial. This study aimed to conduct a meta‐analysis of randomized controlled trials to assess the anti‐inflammatory effects of vitamin D in patients with CKD. Methods We searched Embase, Science Citation Index, Medline, Cochrane Central Register of Controlled Trials, and Clinical Trial Registries for randomized controlled trials that comparing vitamin D with control groups for inflammatory markers in patients with CKD. Subgroup analysis was performed based on treatment duration (short‐term treatment, long‐term treatment), type of patients (predialysis CKD, dialysis, kidney transplant), 25(OH)D levels (25(OH)D deficiency or normal 25(OH)D), and methods of C‐reactive protein (CRP) test (standard CRP test or high‐sensitivity CRP [hs‐CRP] test). Results Eighteen trials with 1834 patients were included in the present study. There were no significant differences between the vitamin D group and control group for CRP (WMD, −0.3 mg/L; 95% CI, −0.81 to 0.22, p = 0.26, I 2 = 62%), interleukin‐6 (IL‐6) (WMD, −1.07 pg/ml; 95% CI, −2.44 to 0.30, p = 0.12, I 2 = 52%), and tumor necrosis factor‐α (TNF‐α) (WMD, −0.00 pg/ml; 95% CI, −0.36 to 0.35, p = 0.99, I 2 = 0%) in patients with CKD. Subgroup analysis showed vitamin D can improve hs‐CRP, but not CRP. The rest of subgroups showed that no significant differences were observed between the vitamin D group and control group based on 25(OH)D levels, treatment duration, and predialysis CKD or dialysis patients. Conclusion This meta‐analysis demonstrates that vitamin D supplementation does not have anti‐inflammatory effects in CKD patients. Well‐designed randomized controlled trials with large samples are required to confirm this conclusion. It is still needed to find an effective treatment for inflammatory state in CKD.