The effect of antioxidants supplementation on oxidative stress and proinflammatory biomarkers in patients with chronic kidney disease: a systematic review and meta-analysis

OBJECTIVE: This systematic re-view and meta-analysis aimed to address the effect of antioxidant supplementation on oxidative stress and proinflammatory biomarkers in patients with Chronic Kidney Disease (CKD).MATERIALS AND METHODS: Systematic literature searches from the date of inception up to September 16th, 2022, were performed on PubMed, SCOPUS, and the Cochrane Central Register of Controlled Trials using relevant key-words, i.e., "Chronic Kidney Disease " and "anti-oxidants ", and "supplementation ". All studies relevant to the selection criteria were included in the analysis, focusing on any type of oxidative stress and proinflammatory bio-markers. A meta-analysis of included literature was conducted if sufficient data was obtained. RESULTS: This systematic review involved 32 published studies, with most having a Jadad score of & GE; 3 (65.6%). Only studies on antioxidants, i.e., polyphenols (n=5) and vitamin E (n=6) in cur-cumin/turmeric, were sufficient to be included in a meta-analysis. Curcumin/turmeric supplementation was found to significantly reduce the serum c-reative protein (CRP) [standardized mean difference (SMD)-0.5238 (95% CI:-1.0495, 0.0019); p = 0.05; I2 = 78%; p = 0.001]. Similarly, vitamin E supplementation was found to significantly reduce the serum CRP [SMD-0.37 (95% CI:-0.711,-0.029); p = 0.03; I2= 53%; p = 0.06] , but not serum inter-leukin-6 (IL-6) [SMD-0.26 (95% CI:-0.68, 0.16); p = 0.22; I2 = 43%; p = 0.17] and malondialdehyde (MDA) content [SMD-0.94 (95% CI:-1.92, 0.04); p = 0.06; I2= 87%; p = 0.0005]. CONCLUSIONS: Our review suggests that curcumin/turmeric and vitamin E supplements effectively lower serum CRP levels in CKD pa-tients, particularly those undergoing chronic di-alysis (CKD-5D). Higher scales of randomized controlled trials (RCTs) are still needed for oth-er antioxidants due to inconclusive and contra-dicting results.