ScienceDaily (July 3, 2008) —
More evidence for the beneficial effect of green tea on risk factors
for heart disease has emerged in a new study. The study found that the
consumption of green tea rapidly improves the function of (endothelial)
cells lining the circulatory system; endothelial dysfunction is a key
event in the progression of atherosclerosis.
The study, performed by Dr Nikolaos Alexopoulos and colleagues at
the 1st Cardiology Department, Athens Medical School in Greece, was a
randomised trial involving the diameter measurement (dilatation) of the
brachial artery of healthy volunteers on three separate occasions –
after taking green tea, caffeine, and hot water (for a placebo effect).
The measurements were taken at 30, 90 and 120 minutes after
consumption. Dilatation of the brachial artery as a result of increased
blood flow (following a brief period of ischaemia of the upper limb) is
related to endothelial function and is known to be an independent
predictor of cardiovascular risk.1
Results showed that endothelium-dependent brachial artery dilatation
increased significantly after drinking green tea, with a peak increase
of 3.9 per cent 30 minutes after consumption. The effect of caffeine
consumption (or hot water) was not significant.
While black tea has been associated with improved short and
long-term endothelial performance, this is the first time that green
tea has been shown to have a short-term beneficial effect on the large
arteries. Another study has already shown that green tea reverses
endothelial dysfunction in smokers.
Green tea, which originates in China but is now consumed throughout
the world, is made with pure leaves, and has undergone little
oxidisation during processing. The cardiovascular benefits of all teas
– as well as dark chocolate and red wine – are attributed to the
flavonoids they contain and their antioxidant activity.2
However, says investigator Dr Charalambos Vlachopoulos, flavonoids in
green tea are probably more potent antioxidants than in black tea
because there has been no oxidisation.
"These findings have important clinical implications," says Dr
Vlachopoulos. "Tea consumption has been associated with reduced
cardiovascular morbidity and mortality in several studies. Green tea is
consumed less in the Western world than black tea, but it could be more
beneficial because of the way it seems to improve endothelial function.
In this same context, recent studies have also shown potent
anticarcinogenic effects of green tea, attributed to its antioxidant
- The study measured flow-mediated dilatation of the
brachial artery, which is predominantly dependent on the release of
nitric oxide from the endothelium and represents a well accepted
estimate of endothelial function. Measurement of the brachial arteries
was performed by high-resolution ultrasound.
are naturally found in many plants and have been shown to have many
different biological effects in humans. Their antioxidant effects have
been found in red wine, red grapes and dark chocolate. Oxidative
stress, which has been associated with many human diseases, can be
reversed by antioxidant intake.
- Alexopoulos et al. The acute effect of green tea consumption on endothelial function in healthy individuals. European Journal of Cardiovascular Prevention & Rehabilitation, 2008; 15 (3): 300 DOI: 10.1097/HJR.0b013e3282f4832f
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