What is so special about green tea? Experts say this tea, which is rich in catechin polyphenols (i.e. compounds that have antioxidant activity), helps lower bad cholesterol levels, kills cancer cells and fights heart disease. New research by a team at the University of Athens Medical School in Greece adds more weight to the latter, highlighting that drinking green tea (Camellia sinesis) improves the function of endothelial cells lining the circulatory system. When endothelial cells dysfunction, atherosclerosis advances, thus increasing cardiovascular risk. The findings were recently published in the European Journal of Cardiovascular Prevention and Rehabilitation.

Researcher Dr Nikolaos Alexopoulos and colleagues from the 1st Cardiology Department carried out a randomised trial involving the dilatation (i.e. diameter measurement) of the brachial artery of healthy volunteers three separate times: post consumption of green tea; caffeine and hot water. The hot water was used for a placebo effect. The researchers measured the volunteers' dilatation 30, 90 and 120 minutes after they had drunk the liquids.

It should be noted that when blood flow increases, the dilatation of the brachial artery is linked to endothelial function. According to the researchers, the dilatation is considered as being an independent predictor of cardiovascular risk.

Based on the findings, green tea consumption increased the brachial artery dilatation considerably. The dilatation rose 3.9% just after the 30-minute mark. Neither caffeine nor hot water consumption showed any marked results.

'These findings have important clinical implications,' team investigator Dr Charalambos Vlachopoulos explained. 'Tea consumption has been associated with reduced cardiovascular morbidity and mortality in several studies.'

While past studies have shown that better endothelial performances have emerged with black tea consumption, it is now clear that green tea has a short-term beneficial effect on the large arteries, the researchers said.

'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,' Dr Vlachopoulos said. 'In this same context, recent studies have also shown potent anti-carcinogenic effects of green tea attributed to its antioxidant properties.'

Native to China, green tea is made from unfermented pure leaves and reportedly contains the highest concentration of polyphenols. These antioxidants fight 'free radicals', compounds that wreak havoc on the human body. But a number of environmental toxins, such as sun, air pollution and cigarettes, also have the capacity to adversely affect the body. Green tea, whose oxidation of the leaves during the processing is minimal, contributes to the neutralisation of free radicals and may lessen or even help curtail damage incurred to the body.

The research carried out by the Greek researchers may also be instrumental in encouraging both domestic and foreign watchdogs to approve petitions from researchers allowing tea labels to claim that green tea reduces cardiovascular risk. A case in point is the US Food and Drug Administration (FDA) which red-lighted such a petition in 2006. The FDA commented that there was not enough evidence to support claims that green tea can reduce such risk.

European Journal of Cardiovascular Prevention & Rehabilitation - Wolters Kluwer Health

Source: Community R&D Information Service (CORDIS)