Several studies have been reported in the few months that reveal a variety of health benefits achieved by green tea polyphenols (GTP). The most recent two studies find reduced risks of certain cancers in both men and women, including a reduction in the chances of getting breast or prostate cancer.
The most well-known compound in green tea is known as epigallocatechin-3 gallate, or EGCG, an antioxidant which is thought to ward off the body-cell damage that can lead to cancer and other diseases. Researchers have recently trademarked another compound with anti-cancer properties called Polyphenon E which contains several of the GTP’s. Combined, the positive effects of green tea may include a reduction in such cancers as colon, stomach, and throat cancers as well as breast and prostate.
In a study published in the American Journal of Clinical Nutrition, EGCG is thought to be responsible for a 14% decrease in the risk of developing digestive cancers in women. Wei Zheng, who heads the department of epidemiology at Vanderbilt University School of Medicine, and colleagues followed 69,000 Chinese women over the course of eleven years. About 19,000 of the women reported being “regular” green-tea drinkers, meaning they consumed it more than three times a week.
Those who had consumed green tea the longest (at least 20 years) were 27% less likely than non-drinkers to develop any type of digestive system cancer and 29% less likely to develop colorectal cancer.
Of course the women in the study had other factors in their favor as well, such as being non-smokers, eating more fruits and vegetables, exercising more and being better educated. But the study did attempt to account for that, and Zheng notes that this study adds to the “strong laboratory evidence” that green tea has the potential to fight cancer.
A separate study by Susanne Henning PhD RD, an adjunct professor at the David Geffen School of Medicine at the University of California Los Angeles, builds on previous studies evaluating the effect of green tea in men with regards to prostate cancer. Sixty-seven men set to undergo a prostatectomy (the removal of an enlarged cancerous prostate) consumed wither six cups of brewed green tea or water daily for three to eight weeks. The results demonstrated that the serum prostate-specific antigen (PSA) concentrations were considerably smaller in the green tea drinkers.
Lastly, Katherine Crew MD, an assistant professor of medicine and epidemiology at Columbia University Medical Center, tested a manufactured extract of GTP’s commercially known as Polyphenon E on women 40 women with hormone receptor-negative breast cancer. The doses in the study were equivalent to eight to 24 cups of pure green tea. The women receiving the product had significantly lower levels of tumor growth factors after two months of treatment.
"This study was too small to say for sure if green tea will prevent breast cancer, but it may move us forward in terms of understanding antitumor mechanisms," Crew said.
In addition to ECGC, green tea contains epicatechin (EC), Epigallocatechin (EGC), and epicatechin gallage (ECG) which combined are called green tea catechins (GTC). Green tea also contains three kinds of flavonoids: kaempferol, quercetin, and myricetin. Biochemically, all of these green tea polyphenols have four main properties – antioxidant, anticarcinogen, anti-inflammatory, and anti-radiation.
Green tea is safe for most people in moderate amounts, but keep in mind that it does contain vitamin K which could interfere with drugs that prevent blood clotting, such as warfarin (Coumadin). The tea and its extracts also contain caffeine. It is wise to talk with your doctor first if you have a chronic medical condition for which you take medication before starting a green tea regimen.
- Wei Zheng et al. Prospective cohort study of tea consumption and risk of digestive system cancers: results from the Shanghai Women's Health Study. Am J Clin Nutr November 2012 vol. 96 no. 5 1056-1063
- A73: Evaluating tissue biomarker effects of an oral green tea extract, Polyphenon E, using reverse phase protein array in women with operable breast cancer. Kimberly A. Ho, Katherine D. Crew et al. Columbia University Medical Center, New York, NY, Louisiana State University Health Sciences Center, Shreveport, LA. Presented at the American Association for Cancer Research (AACR) (2012, October 18).
- American Association for Cancer Research (AACR) (2012, October 18). Green tea reduced inflammation, may inhibit prostate cancer tumor growth, research finds. ScienceDaily. Retrieved October 24, 2012, from http://www.sciencedaily.com¬/releases/2012/10/121018121956.htm