Tea consumption and risk of cardiovascular outcomes and total mortality: a systematic review and meta-analysis of prospective observational studies.
Studies that investigated the association between tea consumption and the risk of major cardiovascular events have reported inconsistent results. We conducted a meta-analysis of prospective observational studies in order to summarize the evidence regarding the association between tea consumption and major cardiovascular outcomes or total mortality. In July 2014, we performed electronic searches in PubMed, EmBase, and the Cochrane Library, followed by manual searches of reference lists from the resulting articles to identify other relevant studies. Prospective observational studies that reported effect estimates, with 95 % confidence intervals (CIs), for coronary heart disease (CHD), stroke, cardiac death, stroke death, or total mortality for more than two dosages of tea consumption were included. A random-effects meta-analysis was performed to determine the risk of major cardiovascular outcomes associated with an increase in tea consumption by 3 cups per day. Of the 736 citations identified from database searches, we included 22 prospective studies from 24 articles reporting data on 856,206 individuals, and including 8,459 cases of CHD, 10,572 of stroke, 5,798 cardiac deaths, 2,350 stroke deaths, and 13,722 total deaths. Overall, an increase in tea consumption by 3 cups per day was associated with a reduced risk of CHD (relative risk [RR], 0.73; 95 % CI: 0.53-0.99; P = 0.045), cardiac death (RR, 0.74; 95 % CI: 0.63-0.86; P < 0.001), stroke (RR, 0.82; 95 % CI: 0.73-0.92; P = 0.001), total mortality (RR, 0.76; 95 % CI: 0.63-0.91; P = 0.003), cerebral infarction (RR, 0.84; 95 % CI: 0.72-0.98; P = 0.023), and intracerebral hemorrhage (RR, 0.79; 95 % CI: 0.72-0.87; P < 0.001), but had little or no effect on stroke mortality (RR, 0.93; 95 % CI: 0.83-1.05; P = 0.260). The findings from this meta-analysis indicate that increased tea consumption is associated with a reduced risk of CHD, cardiac death, stroke, cerebral infarction, and intracerebral hemorrhage, as well as total mortality.