Study is first to show that green tea catechins detoxify cancerous compounds
The August, 2007 issue of the American Association for Cancer Research journal Cancer Epidemiology, Biomarkers & Prevention reported the finding of researchers at the Arizona Cancer Center that catechins derived from green tea help detoxify cancer-causing compounds. The discovery may help explain the cancer preventive effect of green tea found in a number of studies.
University of Arizona research associate professor H.-H. Sherry Chow, PhD and associates studied the effect of a green tea polyphenol concentrate on the production of enzymes belonging to the glutathione S-transferase (GST) family, which render cancer-causing molecules inert. “They actually convert known carcinogens to nontoxic chemicals, and studies have shown a correlation between deficient expression of these enzymes and increased risk of developing some cancers,” Dr Chow explained. “Expression of this enzyme varies dramatically in people due to genetic variation and environmental factors.”
After a one-month period during which no tea products were consumed, 42 healthy men and women were given tea polyphenol capsules containing the amount of catechins found in 8 to 16 cups of green tea. The dosage provided 800 milligrams epigallocatechin gallate (EGCG), a catechin associated with anticancer benefits in previous research. Participants were instructed to consume the capsules on an empty stomach to maximize oral absorption. Lymphocyte glutathione S-transferase levels were measured in blood samples drawn at the beginning and end of the four week treatment period.
The team found an increase in glutathione S-transferase activity of as much as 80 percent in those whose levels were lowest at the beginning of the study. “Green tea catechins somehow increase gene expression of these enzymes, which can be an advantage to people with low levels to start with,” stated Dr Chow. “This is the first clinical study to show proof that chemicals in green tea can increase detoxification enzymes in humans. There may be other mechanism in play by which green tea may protect against cancer development, but this is a good place to start.”
Complementary alternative medical therapies (CAM) is a collective term for an array of remedies that lie outside what is traditionally considered conventional medical treatment for cancer. The use of CAM as a component of integrated cancer treatment regimens may help patients reduce the side effects associated with conventional cancer treatments, alleviate symptoms, enhance immune function, and provide greater quality of (and control over) life (Deng G et al 2004, 2005).
Catechins and theaflavins, compounds found in green and black teas, have anti-cancer properties (Yang CS et al 2005). Clinical studies have shown that consuming five or more cups a day of green tea reduces the risk of developing breast cancer, and may help reduce the risk of recurrence in breast cancer survivors (Seely D et al 2005).
Consumption of green tea also significantly improves the survival of ovarian cancer patients (Zhang M et al 2004) and reduces the risk of developing cancers of the lung and prostate (Bonner MR et al 2005; Doss MX et al 2005). Such is the strength of data demonstrating green tea’s potential in preventing cancer that Japanese researchers are trying to develop a strategy, based on green tea consumption, for delaying cancer onset in the Japanese population, as well as reducing the risk of recurrence in cancer survivors (Fujiki H 2005).
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As Chief Medical Correspondent for CNN, Dr. Gupta is currently the most famous and listened to doctor on the planet. Millions of viewers learn daily about advances in medicine that can change their lives. Additionally, Dr. Gupta is assistant professor of neurosurgery at Emory University Hospital and associate chief of neurosurgery at Grady Memorial Hospital, where he practices.
Most recently, Dr. Gupta embarked upon a remarkable quest to investigate “new discoveries in the search for immortality to help you age less today.”
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