The effects of catechin on endothelial function: A systematic review and meta-analysis of randomized controlled trials

The findings of trials investigating the effect of catechin on endothelial function are controversial. This meta-analysis of randomized controlled trials (RCTs) was performed to summarize the existing evidence and determine the effects of catechin supplementation on endothelial function. Two authors independently searched electronic databases including MEDLINE, EMBASE, Cochrane Library, and Web of Science from inception until March 2019, in order to find relevant RCTs. The quality of selected RCTs was evaluated using the Cochrane Collaboration risk of bias tool. Cochrane's Q test and I-square (I-2) statistic were used to determine the heterogeneity of included trials. Data were pooled using a random-effects model and weighted mean difference (WMD) was considered as the overall effect size. A total of 16 studies with 22 effect sizes were included in this meta-analysis. A significant increase in flow mediated dilation (FMD) in 10 studies was found after catechin supplementation including 13 effect sizes (WMD: 1.53; 95% CI: 0.93, 2.14). The pooled analysis of 7 effect sizes from 4 studies showed a significant reduction in pulse wave velocity (PWV) after catechin supplementation (WMD: -0.32; 95% CI: -0.44, -0.20) and combining 5 effect sizes from 3 studies in augmentation index (AI) (WMD: -3.57; 95% CI: -6.40, -0.74). Catechin supplementation significantly increased FMD, and significantly reduced PWV and AI, but did not affect other markers of endothelial function.