Effect of green tea consumption on blood pressure: a meta-analysis of 13 randomized controlled trials

The studies investigating the effects of green tea on blood pressure (BP) have generated inconsistent results. The aim of this study is to quantitatively evaluate the effects of green tea on BP control. PubMed, Embase, and the Cochrane Library (updated to March 2014) were searched for randomized controlled trials evaluating the effects of green tea on BP. Pooled effect of green tea consumption on BP was evaluated using fixed-effects or random-effects model. Thirteen trials comprising a total of 1,367 subjects were included in the current meta-analysis. The overall outcome of the meta-analysis suggested that green tea consumption significantly decrease systolic blood pressure (SBP) level by -1.98 mmHg (95% CI: -2.94, -1.01 mmHg; P < 0.001). Compared with the control group, green tea also showed a significant lowering effect on diastolic blood pressure (DBP) in treatment group (-1.92 mmHg; 95% CI: -3.17, -0.68 mmHg; P = 0.002). Subgroup analyses further suggested that the positive effect of green tea polyphenols on BP was only showed in studies using a low-dose green tea polyphenol, with the long-term intervention duration or ruling out the confounding effects of caffeine. The meta-analysis suggested that green tea consumption had a favorable effect on decrease of BP.