Blood vessels are lined by a thin layer of cells known as the endothelium, which plays a key role in regulating blood flow, vascular tone, and inflammatory signaling. When endothelial function is impaired, circulation can suffer and cardiovascular risk increases.
A randomized, placebo-controlled study published in the Circulation Journal (2010 Feb 4; epub ahead of print) examined the effects of green tea catechins (GTC)—antioxidant compounds found in green tea—on endothelial function in 30 smokers with no major health complaints. Smoking is known to impair endothelial function, making this a useful model for studying vascular responses.
Participants were randomly assigned to one of three groups for two weeks: a low-dose GTC group (80 mg/day), a high-dose GTC group (580 mg/day), or a placebo group. Endothelial function was assessed by measuring forearm blood flow responses to acetylcholine and sodium nitroprusside, substances used to evaluate blood vessel dilation.
Only the group receiving the higher dose of green tea catechins showed a significant increase in blood flow response, indicating improved vascular reactivity and circulation. This group also demonstrated increased nitric oxide availability, a key molecule involved in vasodilation. In addition, levels of inflammatory markers—including C-reactive protein—were reduced.
These improvements were not observed in the placebo group or in participants receiving the lower dose of green tea catechins. The findings suggest that higher intakes of green tea catechins may influence endothelial function, nitric oxide signaling, and inflammatory markers, at least in the short term and within this specific population.
