Effects of tea intake on blood pressure: A meta-analysis of 21 randomized controlled trials

JACC - Journal of the American College of Cardiology, 10/22/2014

Gang L, et al.

The authors undertook a meta–analysis of randomized controlled trials to determine changes in systolic and diastolic BP due to the intake black and green tea. The meta–analysis showed that long–term (≥12 weeks) ingestion of a tea (green and black tea) resulted in a significant reduction in systolic and diastolic BP.

Methods

• MEDLINE, EMBASE, and the Cochrane Controlled Trials Register were searched from 1966 until January 2014 for studies in parallel group or crossover design in which BP was assessed before and after receiving black or green tea for at least 1 week.
• The weighted mean difference was calculated for net changes in BP by using fixed–effects or random–effects models.
• Previously defined subgroup analyses were performed to explore the influence of study characteristics.

Results

• 21 eligible randomized controlled trials with 1323 subjects were enrolled.
• After the tea intake, the pooled mean systolic and diastolic BP were –1.8 mmHg (95% confidence interval [CI], –2.4– –1.1 mmHg) and –1.4mmHg (95% CI, –2.2– –0.6 mm Hg) lower, respectively, compared with the tea–free controls.
• Subgroup analyses showed that the BP–lowering effect was apparent in the subjects who consumed a tea over a median of 12 weeks (systolic/diastolic BP, –2.6/–2.1 mmHg, both P <0 .001="" li="">
• Stratified by type of tea, green tea significantly reduced systolic and diastolic BP of –2.1 (95% CI, –2.9– –1.2) and –1.7 (95% CI, –2.9– –0.5) mm Hg, and black tea significantly reduced systolic and diastolic BP of –1.4 (95% CI, –2.4– –0.4) and –1.1 (95% CI, –1.9– –0.2) mm Hg, respectively.
• The benefits of tea intake were not influenced by ethnicity, treatment dose of tea catechins, individual health status, or caffeine intake.