Introduction: The effect of tea consumption on cardiovascular risk has not been defined yet, although there is evidence of a beneficial effect attributed to its flavonoid content. Endothelial dysfunction is a key event in the pathogenesis of atherosclerosis. The aim of the study was to evaluate the effect of green tea on endothelial function.

Methods: Thirteen apparently healthy subjects (age 32±3 years) with no risk factors for cardiovascular disease (except from 6 smokers) were studied at 3 sessions: (i) one with 6 gram of green tea, (ii) one with 125 mg of caffeine (the content of caffeine in green tea preparation) and (iii) one after placebo (hot water). Flow-mediated dilatation of the brachial artery was examined, using ultrasonography at baseline, at 30 min (peak plasma concentration of caffeine) and at 90 and 120 min (peak plasma concentration of flavonoids) after each intervention.

Results: The effect of green tea (or caffeine) on each variable is better described as changes in the response of each variable, where response is defined as net green tea (or caffeine) minus placebo values at each time point. Resting and hyperemic diameter of the brachial artery did not change significantly either with green tea or caffeine. Flow-mediated dilatation was significantly increased with green tea (by 2.46%, p < 0.02) but not with caffeine.

Conclusions: Green tea has an acute beneficial effect on endothelial function in healthy individuals. This may, at least partly, contribute to the beneficial effect of tea on cardiovascular risk.