Objective Epidemiological evidence has linked consumption of black tea,
produced from Camellia sinensis, with a reduced risk of cardiovascular
diseases. However, intervention studies on the effects of tea consumption on
blood pressure (BP) have reported inconsistent results. Our objective was to
conduct a systematic literature review with meta-analysis of controlled human
intervention studies examining the effect of tea consumption on BP. Methods We
systematically searched Medline, Biosis, Chemical Abstracts and EMBASE
databases through July 2013. For inclusion, studies had to meet the following
pre-defined criteria: 1) placebo controlled design in human adults, 2) minimum
of 1 week black tea consumption as the sole intervention, 3) reported effects
on systolic BP (SBP) or diastolic BP (DBP) or both. A random effects model was
used to calculate the pooled overall effect of black tea on BP. Results Eleven
studies (12 intervention arms, 378 subjects, dose of 4–5 cups of tea) met our
inclusion criteria. The pooled mean effect of regular tea ingestion was −1.8
mmHg (95% CI: −2.8, −0.7; P = 0.0013) for SBP and −1.3 mmHg (95% CI: −1.8,
−0.8; P<0.0001) for DBP. In covariate analyses, we found that the method of
tea preparation (tea extract powders versus leaf tea), baseline SBP and DBP,
and the quality score of the study affected the effect size of the tea
intervention (all P<0.05). No evidence of publication bias could be detected.
Conclusions Our meta-analysis indicates that regular consumption of black tea
can reduce BP. Although the effect is small, such effects could be important
for cardiovascular health at population level
