Effect of green tea supplementation on blood pressure: A systematic review and meta-analysis of randomized controlled trials

BACKGROUND: Although evidence from animal and observational studies has supported the beneficial effects of green tea intake for lowering blood pressure (BP), randomized placebo-controlled trials (RCTs) have yielded conflicting results. In this meta-analysis of RCTs, we aimed to assess the effects of green tea supplementation on measures of BP control. METHODS: The PubMed, Embase, and Cochrane Library databases were electronically searched from inception to August 2019 for all relevant studies. The results were pooled using the generic inverse-variance method with random-effects weighting and expressed as mean differences (MDs) with 95% confidence intervals (CIs). The quality of studies was assessed using the Jadad score. Publication bias was evaluated using funnel plots, Egger test, and Begg test. RESULTS: Twenty-four trials with 1697 subjects were included in the meta-analysis. The pooled results showed that green tea significantly lowered systolic BP (SBP; MD: −1.17 mm Hg; 95%CI: −2.18 to −0.16mm Hg; P = .02) and diastolic BP (DBP; MD: −1.24 mm Hg; 95%CI:−2.07 to −0.40mm Hg; P = .004). Significant heterogeneity was found for both SBP (I(2) = 43%) and DBP (I(2) = 57%). In addition, no evidence of significant publication bias was found from funnel plots or Egger test (P = .674 and P = .270 for SBP and DBP, respectively). CONCLUSION: Overall, green tea significantly reduced SBP and DBP over the duration of the short-term trials. Larger and longer-term trials are needed to further investigate the effects of green tea supplementation on BP control and clinical events.