Green tea, is the unfermented product of the Camellia sinensis plant. Oolong tea is partially fermented, and black tea is fully fermented. Green tea is not fermented at all. Fermentation may reduce the levels of some compounds, such as antioxidants, in the tea. The 4 main polyphenols found in tealeaves are epigallocatechin gallate (EGCG), epigallocatechin (EGC), epicatechin gallate (ECG), and epicatechin (EC). Epigallocatechin gallate (EGCG) is the most powerful of these catechins. The active constituent is EGCG (epigallocatechin-3-gallate), which accounts for 40 percent of the total polyphenol content of green tea extract.
According to scientists at the University of Kansas, the antioxidant capacity of EGCG is approximately 100 times greater than that of vitamin C and 25 times greater than that of vitamin E in protecting DNA from the kind of free radical damage that is thought to increase the risk of cancer. Also, it is thought that epigallocatechin gallate plays an critical role in inhibiting DNA synthesis and cell replication, both imperative for the survival of cancer cells.
At the molecular level, epigallocatechin gallate directs cell signals that block dangerous activity that could lead to the uncontrolled growth characteristic of cancer cells. Epigallocatechin gallate selectively induces apoptosis in human carcinoma cell lines. Inhibits telomerase and DNA methyltransferase, two enzymes involved in cancer gene expression and cellular immortality. Anti-oxidant action protects cells from lipid peroxidation and DNA damage induced by reactive free radicals. Curcumin shows synergism with catechins in colonic tumor cells and human larynx carcinoma cells. In vitro experiments suggest that quercetin can enhance the antiproliferative impact of catechins in prostate cells in a synergistic manner. Vitamin C, shows synergism with epigallocatechin gallate in suppressing adenocarcinoma proliferation.
Some experiments shown that catechins inhibits a growth factor receptor named HER2, which is present in excess in approximately 30 percent of breast cancers and is associated with poor outcomes. When non-Hodgkin’s lymphoma cells were transplanted into mice, prevented 50 percent of the tumors from taking hold and important inhibited growth of the tumors. In vitro findings show that concentrations of 30 mcg/mL EGCG and EGC inhibit lipoxygenase-dependent arachidonic acid metabolism by 30-75 percent in normal human colon mucosa and colon cancers. A study of 18,000 Chinese men found that men who drank green tea frequently had a 50% lower risk of developing stomach cancer as compared to men who did not drink tea. In a study reported in ‘Cancer Science‘ in 2011 wrote EGCG may help treat cancer when used with anticancer medications.
In a case-control study involving 130 prostate cancer patients and 274 hospital controls, men drinking the most green tea were found to have an 86% decreased risk of prostate cancer compared, to those drinking the least. In a study reported in the December 2004 edition of the “International Journal of Cancer” found that EGCG significantly inhibited, in a dose-dependent manner, the production of PSA (prostate-specific antigen), a marker for prostate cancer risk. In Japan, a study of 500 women with Stage I and Stage II breast cancer found that increasing their green tea consumption before and after surgery significantly lowered the risk of recurrence.
EGCG activates endothelial nitric oxide synthase in cells lining blood vessels, or endothelial cells. Increased release of nitric oxide causes smooth muscle within the blood vessel wall to relax, therefore, increasing the diameter of the blood vessel and improving blood flow. Catechins inhibits platelet aggregation and adhesion via effects that differ. First, green tea inhibits thromboxane A2 formation. Also, inhibits another clotting agent called platelet activating factor (PAF). In addition, green tea improves the function of endothelial cells. Researchers in a study have found that people who drink green tea have better blood vessel function just 30 minutes later. This research, “European Journal of Cardiovascular Prevention and Rehabilitation” was reported in the journal.
Dose-response relationships observed in sundry epidemiological studies have indicated that pronounced cardiovascular effects can be obtained by regular consumption of 5 to 6 cups of green tea per day. Also, studies using similar amounts of green tea, containing 200-300 mg of epigallocatechin gallate, have showed its efficacy for maintaining cardiovascular. When compared to drinking less than one cup per day, daily consumption of five or more cups of green tea was associated with a 16% reduction in mortality from all causes and a 26% reduction in mortality from cardiovascular diseases.
Findings from different animal-based and human studies suggest that epigallocatechin gallate may help treat viral hepatitis. Pure (+)-catechin (Catergen) has been used to treat hepatitis since 1976. This product has been shown to be an effective immune stimulator, promoting activation of macrophages, cytotoxic-T-lymphocytes, and NK (natural killer) cells in mice in a dose-dependent manner. 57 patients with chronic liver diseases of various etiology were treated with catergen given in a dose of 3 tablets (1.5 g) a day throughout three months. At the end of the experimental period, was shown that significantly catergen improved some biochemical characteristics of the blood and indicators of the antipyrine test in people with compensated liver cirrhosis of the viral and alcoholic etiology.
According to German scientists, epigallocatechin-3-gallate (EGCG) may provide an antiviral measure to prevent HCV reinfection following liver transplantation. ‘EGCG inhibits HCV cell entry by blocking viral attachment and may offer a new approach to prevent HCV infection, particularly reinfection liver transplantation’. Sandra Ciesek from the Hannover Medical School in Germany said. In lab tests, epigallocatechin-3-gallate, was found to prevent HIV from attacking T-Cells. Researcher Professor Mike Williamson, made the following statement; this research shows that green tea, could slow down the spread of HIV and could reduce the risk of becoming infected by HIV.
One of the important compounds found in green tea has a strong capability to increase the number of “regulatory T cells” that play a critical role in immune function and suppression of autoimmune illness, according to research in the Linus Pauling Institute. Lab experiments done with mice, showed that treatment with epigallocatechin gallate significantly increased the numbers and frequencies of regulatory T cells found in spleen and lymph notes, and in the process helped to control the immune response.
Daily intake of catechins efficiently protects the brain from irreversible damage due to cerebral ischemia, and consequent neurologic deficits. In a the study, reported in the September 2010 Journal of Clinical Neuroscience, lab mice with Parkinson’s disease were given the epigallocatechin-3-gallate, and nerve cell death was reduced by 50 %. Animal-based studies, mice bred to develop Alzheimer’s disease developed up to 54 % less beta-amyloid buildup in their brains when they were given daily injections EGCg.
For a green tea extract standardized for 80 % polyphenols and 55 % epigallocatechin gallate, a daily dose of 300 to 400 mg green tea extracts is recommended. The generally used dose of green tea is based on the amount consumed in Asian countries, providing 240-320 mg (three cups a day) of the active ingredients polyphenols.