Effect of Vitamins C and E Co-Supplementation on Serum C-Reactive Protein Level: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Studies assessing the effect of vitamin C and E co-supplementation on levels of circulating C-reactive protein (CRP) show contradictory results. We carried out a systematic review and meta-analysis of randomized controlled trials (RCTs) to assess the effect of vitamin C and E co-supplementation on CRP. A systematic search was carried out using PubMed, Scopus, Ovid, Cochrane, Embase, and the Web of Science without any language or time restriction (until 31 March 2019) to retrieve RCTs that examined the effect of vitamin C and E co-supplementation on CRP. A meta-analysis was carried out using a random effects model, and I² indexes were used to evaluate the heterogeneity. The search yielded 5,134 publications, including 8 eligible RCTs. The results indicate that vitamin C and E co-supplementation does not significantly impact levels of serum CRP [weighted mean difference and 95% confidence interval with random effects model analysis: −0.22 mg/L (−0.85, 0.41), P=0.5]. Subgroup analysis demonstrated that vitamin C and E co-supplementation significantly reduced serum CRP in participants ≥30 years of age, but significantly increased serum CRP in participants <30 years of age. The results of this meta-analysis indicate beneficial effects of vitamins C and E co-supplementation on CRP in participants ≥30 years of age, and not in younger participants. To confirm these results, further well-designed RCTs are needed.