The effects of vitamin D treatment on glycemic control, serum lipid profiles, and C-reactive protein in patients with chronic kidney disease: a systematic review and meta-analysis of randomized controlled trials

Purpose Insulin resistance, dyslipidemia and increased systemic inflammation are important risk factors for chronic kidney disease (CKD). Hence, vitamin D administration might be an appropriate approach to decrease the complications of CKD. Randomized controlled trials assessing the effects of vitamin D supplementation or treatment on glycemic control, lipid profiles, and C-reactive protein (CRP) among patients with CKD were included. Methods Two independent authors systematically searched online databases including EMBASE, Scopus, PubMed, Cochrane Library, and Web of Science in November 2018 with no time restriction. Cochrane Collaboration risk of bias tool was applied to assess the methodological quality of included trials. Between-study heterogeneity was estimated using the Cochran's Q test and I-square (I-2) statistic. Data were pooled using a random-effects model and weighted mean difference (WMD) was considered as the overall effect size. Results Of the 1358 citations identified from searches, 17 full-text articles were reviewed. Pooling findings from five studies revealed a significant reduction in fasting glucose (WMD: - 18.87; 95% CI: - 23.16, - 14.58) and in homeostatic model assessment of insulin resistance (HOMA-IR) through three studies (WMD: - 2.30; 95% CI: - 2.88, - 1.72) following the administration of vitamin D. In addition, pooled analysis revealed a significant reduction in triglycerides (WMD: - 32.52; 95% CI: - 57.57, - 7.47) through six studies and in cholesterol concentrations (WMD: - 7.93; 95% CI: - 13.03, - 2.83) through five studies, following vitamin D supplementation or treatment, while there was no effect on insulin, HbA1c, LDL and HDL cholesterol, and CRP levels. Conclusions This meta-analysis demonstrated the beneficial effects of vitamin D supplementation or treatment on improving fasting glucose, HOMA-IR, triglycerides and cholesterol levels among patients with CKD, though it did not influence insulin, HbA1c, LDL and HDL cholesterol, and CRP levels.