Writing in the Journal of Nutrition, scientists report that the “modest” reduction was observed for regular tea drinkers, compared to non-drinkers, after evaluating the diet of 3454 women with breast cancer and 3474 healthy controls aged between 20 and 74.
The study, led by Martha Shrubsole from Vanderbilt School of Medicine in Nashville, adds to the ever-growing body of science supporting the anti-cancer benefits of green tea and its polyphenols.
Green tea contains between 30 and 40 per cent of water-extractable polyphenols, while black tea (green tea that has been oxidized by fermentation) contains between 3 and 10 per cent. Oolong tea is semi-fermented tea and is somewhere between green and black tea.
The four primary polyphenols found in fresh tealeaves are epigallocatechin gallate (EGCG), epigallocatechin (EGC), epicatechin gallate (ECG), and epicatechin (EC).
Shrubsole and her collaborators from the Shanghai Cancer Institute and the Shanghai Center for Disease Prevention and Control performed the study in Shanghai. All of the women were individually interviewed and their green tea drinking habits, including regularity, tea strength, and quantities consumed, were assessed.
Regular consumption of the beverage was associated with a “slightly decreased risk for breast cancer” of 12 per cent, said the researchers, compared to non-drinkers.
Furthermore, benefits for pre-menopausal women were related to the number of years they had been regular drinkers, and a dose-response was also observed
On the other hand, the researchers found no relationship between a specific genotype called COMT rs4680 AA and breast cancer risk. The enzyme catechol-O-methyltransferase (COMT) is known to catalyse tea polyphenols, and the lower activity associated with COMT rs4680 AA was hypothesised to affect the relationship between green tea and breast cancer risk.
“Drinking green tea may be weakly associated with a decreased risk of breast cancer,” concluded the researchers
In addition to the potential anti-cancer benefits, previous studies have reported a range of health benefits for green tea and its extracts, including the potential to promote weight loss, and protection against Alzheimer's.
European demand for tea extracts is currently surging, having reached 500 metric tonnes by 2003.
This has seen companies such as DSM, with its Teavigo boasting 95 per cent purity of EGCG, and Taiyo International, with its Sunphenon claiming more than 90 per cent purity, position themselves firmly in specific catechin markets.
Source: Journal of NutritionFebruary 2009, Volume 139, Number 2, Pages 310-316“Drinking Green Tea Modestly Reduces Breast Cancer Risk”Authors: M.J. Shrubsole, W. Lu, Z. Chen, X.O. Shu, Y. Zheng, Q. Dai, Q. Cai, K. Gu, Z.X. Ruan, Y.-T. Gao, W. Zheng