Effects of purified anthocyanins supplementation on serum concentration of inflammatory mediators: A systematic review and dose-response meta-analysis on randomized clinical trials

Anthocyanins, due to their antioxidant effects, are candidates to reduce inflammation and the risk of inflammatory diseases. Therefore, through conducting a systematic review and meta-analysis, we tried to find the effect of purified anthocyanins on serum levels of C-reactive protein (CRP), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-alpha). Databases including, ISI Web of Science, Scopus, ClinicalTrials.gov, PubMed, and Cochrane Library were searched up to June 2023. The meta-analysis was done by calculating mean differences and their standard deviations. Calculating the statistical heterogeneity of intervention effects was performed through I-squared statistics and Cochran's Q test. The pooled estimate showed a significant decrease in serum levels of CRP, TNF-alpha, and IL-6 (weighted mean difference (WMD) = -0.12 mg/L, 95% confidence interval (CI) = -0.21 to -0.02, p = 0.013; WMD = -1.37 pg/mL, 95% CI = -1.79 to -0.96; p < 0.001; WMD = -1.43 pg/mL, 95% CI = -1.87 to -1.00; p < 0.001, respectively). Subgroup analysis results revealed purified anthocyanins significantly decreased serum levels of CRP among participants with serum levels of CRP >= 1.52 mg/L, at-risk/unhealthy status, and in trials with intervention duration >= 84 days, anthocyanins dose >= 320 mg/day, and sample size >= 85 subjects. Regarding TNF-alpha and IL-6, out results showed that there was a significant effect of purified anthocyanins on serum levels of TNF-alpha and IL-6 in most subgroups. The results of our study indicated that purified anthocyanins significantly decreased serum levels of CRP, TNF-alpha, and IL-6. However, further high-quality studies are needed to firmly establish the efficacy of purified anthocyanins.