If you drink green tea, you are providing your body with protection against a host diseases brought about by free-radical damage. Several large studies have shown that the antioxidant effects of green tea can help lower the risk of developing cancer of the digestive system, prostate cancer, cervical cancer, and breast cancer in women.
Studies have also shown that green tea also protects against heart disease by lowering cholesterol levels and preventing the blood clots that can lead to atherosclerosis (clogged arteries).
Women experiencing hot flashes associated with menopause may find that drinking green tea morning and night may help reduce their frequency. Limited studies report that green tea helps balance estrogen levels, and which can help prevent not only hot flashes but discourage certain types of breast cancer as well.
Green tea has also been used to prevent tooth decay, increase air low to the lungs in asthma patients, and increase mental alertness (the last two effects are probably due in some part to the caffeine that is naturally found in all teas). Also, several small have shown that green tea extract (GTE) is an appetite suppressant and promotes weight loss in humans. It is now widely available in pharmacies and even some grocery stores in dietary supplements designed to help you lose weight.
Studies have also shown that green tea also protects against heart disease by lowering cholesterol levels and preventing the blood clots that can lead to atherosclerosis (clogged arteries).
Women experiencing hot flashes associated with menopause may find that drinking green tea morning and night may help reduce their frequency. Limited studies report that green tea helps balance estrogen levels, and which can help prevent not only hot flashes but discourage certain types of breast cancer as well.
Green tea has also been used to prevent tooth decay, increase air low to the lungs in asthma patients, and increase mental alertness (the last two effects are probably due in some part to the caffeine that is naturally found in all teas). Also, several small have shown that green tea extract (GTE) is an appetite suppressant and promotes weight loss in humans. It is now widely available in pharmacies and even some grocery stores in dietary supplements designed to help you lose weight.
The cancer-protective effects of green tea have been reported in several population-based studies. For example, cancer rates tend to be low in countries such as Japan where green tea is regularly consumed. However, it is not possible to determine from these population-based studies whether green tea actually prevents cancer in people. Emerging animal and clinical studies are beginning to suggest that EGCG may play an important role in the prevention of cancer.
It has been suggested that EGCG and other tea catechins suppress tumor promotion by inhibiting the release of tumor necrosis factor-alpha, which is believed to stimulate tumor promotion and progression of initiated cells as well as premalignant cells. Furthermore, EGCG was shown to reduce specific binding of both the 12-Otetradecanoylphorbol-13-acetate (TPA)-type and the okadaic acid-type tumor promoters (the two major classes of tumor-promoting agents) to their receptors. This "sealing" effect of EGCG is achieved by its interaction with the phospholipid bilayer of the cell membrane.
When non-Hodgkin's lymphoma cells were transplanted into mice, green tea prevented 50% of the tumors from taking hold and significantly inhibited growth of the tumors.
Bladder cancer
A few studies have examined the relationship between bladder cancer and green tea consumption. In one study that compared people with and without bladder cancer, researchers found that women who drank black tea and powdered green tea were less likely to develop bladder cancer. A follow-up study by the same group of researchers revealed that bladder cancer patients (particularly men) who drank green tea had a substantially better 5-year survival rate than those who did not.
Breast cancer
Studies suggest that EGCG inhibits the growth of breast cancer cells, both in live animals and test tubes.
A Japanese study comparing 472 women with breast cancer who drank differing amounts of green tea indicates that EGCG may decrease both the severity of the initial diagnosis and the likelihood of recurrence. The researchers found that the women with Stage I, II and III breast cancers that drank five or more cups of green tea per day were less likely to have cancer that spread to the nymph nodes. In addition, the greater consumption of green tea by women with Stage I or II breast cancer was associated with lower incidence of recurrence. No correlation was shown with women who had Stage III cancers. Another Japanese study showed less overall incidence of cancer among 8,000 people who drank ten or more cups of green tea a day.
Colorectal cancer
A study at the Linus Pauling Institute at Oregon State University on mice that were genetically predisposed to develop tumors in their intestines revealed after 12 weeks of treatment that mice that were given green tea had significantly fewer tumors than mice that received no treatment (Carcinogenesis, February 2003).
Phenol sulsotransferases are involved in cancer growth, and EGCG was shown to inhibit this activity in a human colon cancer call line (Biol Pharm Bull 2000 Jun;23(6):695-9).
Chinese scientists discovered that EGCG inhibits angiogenesis (the production of new blood vessels) in mice inoculated with human colon cancer. This blocking of new blood vessel growth may be an important part of the overall anti-cancer action of polyphenols, since it impedes tumor growth.
Esophageal cancer Studies in laboratory animals have found that green tea polyphenols inhibit the growth of esophageal cancer cells. However, results of studies in people have been conflicting. In fact, some evidence suggests the hotter the tea (or any other hot beverage), the greater the risk of developing esophageal cancer. However, researchers reporting on a case-control study, found that Chinese men and women who drink green tea have a reduced risk of up to 60 percent of developing esophageal cancer (Journal of the National Cancer Institute, June 1, 1994).
Esophageal cancer Studies in laboratory animals have found that green tea polyphenols inhibit the growth of esophageal cancer cells. However, results of studies in people have been conflicting. In fact, some evidence suggests the hotter the tea (or any other hot beverage), the greater the risk of developing esophageal cancer. However, researchers reporting on a case-control study, found that Chinese men and women who drink green tea have a reduced risk of up to 60 percent of developing esophageal cancer (Journal of the National Cancer Institute, June 1, 1994).
Lung cancer
Consumption of green tea was found to be associated with a reduced risk of lung cancer among non-smokers but not among smokers. Also among non-smokers, the risks of lung cancer decreased with increasing tea consumption. (Epidemiology 2001 Nov; 12(6):695-700).
Treatment of human lung cancer cell line A549 cells with EGCG significantly inhibited the expression levels of hnRNP B1 mRNA and the elevated levels of hnRNP B1 protein, both of which are constitutively elevated in cancer cells. Furthermore, both EGCG inhibited the promoter activity of hnRNP A2/B1 gene expression, preventing lung cancer (International Journal of Onclology 20: 1233-1239, 2002).
Pancreatic cancer
Researchers in Japan determined whether EGCG affects proliferative and invasive activity of human pancreatic carcinoma cells. The results indicate that the growth of all three pancreatic carcinoma cells (PANC-1, MIA PaCa-2 and BxPC-3) was significantly suppressed by EGCG treatment in a dose-dependent manner. EGCG may be a potent biologic inhibitor of pancreatic carcinoma, reducing their proliferative and invasive activity (Pancreas, July 2002).
Prostate cancer
In my opinion, EGCG is the most important component of green tea to the prostate cancer patient. The first evidence of its ability to induce prostate cancer apoptosis (programmed cell death) was published in Cancer Letters back in 1998 (130(1-2):1-7 1998 Aug 14).
Its pharmacologic activity extends beyond its action as an anti-oxidant. EGCG acts against urokinase, an enzyme often found in large amounts in human cancers, inhibits ornithine decarboxylase (a rate-limiting enzyme closely associated with tumor promotion), and blocks type 1 5-alpha reductase (5AR). Inhibitors of 5AR may be effective in the treatment of 5 alpha dihydrotestosterone-dependent abnormalities, such as benign prostate hyperplasia, prostate cancer, and certain skin diseases.
Urokinase breaks down the basement membrane of cell junctions which may be a key step in the process of tumor cell metastasis as well as tumor growth. EGCG attaches to urokinase and prevents these actions.
EGCG was shown to inhibit growth and induce regression of human prostate and breast cancers in athymic mice (Liao S, Umekita Y, Guo J et al. Growth inhibition and regression of human prostate and breast tumors in athymic mice by tea epigallocatechin gallate (Cancer Letters 96:239-243, 1995).
Skin cancer
Studies suggest that EGCG and green tea polyphenols have anti-inflammatory and anti-cancer properties that may help prevent the onset and growth of skin tumors. Topical application of EGCG may prevent UV-B-induced immunosuppression and precancerous cell changes after UV-B exposure (J Leukoc Biol. 2001;69:719-726).
Stomach cancer
Laboratory studies have found that green tea polyphenols inhibit the growth of stomach cancer cells in test tubes. The exposure of human stomach cancer KATO III cells to EGCG led to both growth inhibition and the induction of programmed cell death (apoptosis)
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