Green tea is a beverage made from the unfermented leaves of the Camellia sinensis plant. Green tea is not fermented. Oolong tea is partially, black tea is fully fermented. As a result, green tea contains a high concentration of antioxidants called polyphenols. Green tea also contains alkaloids including caffeine, theophylline and theobromine.
Catechins are polyphenolic antioxidants found in various plants particularly in the leaves of the tea plants. Green tea contains between 30 and 40 % of water-extractable polyphenols, while black tea contains between 3 and 10 %. 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. One cup of green tea supplies 20-35 mg of EGCG.
Food Sources of Catechins
Top of the list is green tea. Other foods containing catechins; red wine, raisins, blueberries, cranberry juice, dark chocolate. A single infusion of green tea contains up to about 200 mg, whereas 1 liter of wine has 300 mg. 100 grams of dark chocolate contains 54 milligrams, blueberries 52 milligrams.
The importance of green tea lies in the fact it is rich in catechin polyphenols, particularly epigallocatechin gallate. In test tubes, catechins are more powerful than vitamin C and E in halting oxidative damage to cells and appear to have other disease-fighting properties. Some researchs have found an association between consuming green tea and a reduced risk for several cancers, including, lung, breast, colon, esophageal, and bladder. Catechins have also proven to have a major impact on important impacting the immune system. This has made it a popular food especially in Asia due to the many green tea benefits.
Green tea contains chemicals recognized as polyphenols, which have antioxidant effects. Catechins are antioxidants with the ability to scavenge reactive oxygen species such as superoxide, the hydroxyl and peroxyl radicals. Some researchs show that the polyphenols most prevalent in green tea are far more potent in suppressing free radicals than vitamins C or E. Catechins antioxidant effect protects against cancer, preventing free radicals from attacking the body cells. In one study published in the November 2004 issue of “Mutation Research“, EGCG’s protective antioxidant effects against several carcinogens were found to be 120 percent stronger than those of vitamin C. In a four month study of heavy smokers involving 100 women and 33 men found that levels of urinary 8-hydroxydeoxyguanosine, a marker of free radical damage to DNA, dropped significantly in individuals drinking green tea.
According to laboratory studies, catechins scavenged oxidants before cell damage occurred, reduced the number and size of tumors, and inhibited the growth of cancer cells. Green tea’s anticancer effects include its ability to inhibit the overproduction of the enzyme cyclooxygenase (COX)-2, a protein whose overproduction has been implicated as a factor in many diseases, including cancer. 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. Another study published in January 2007 in ‘Cancer Letters‘ found that green tea polyphenols protected against the spread of breast cancer in both human breast cancer cells in vitro and in vivo. In a study published in ‘Cancer Science‘ in 2011 wrote EGCG may help treat cancer when used with anticancer drugs.
EGCG causes tumor cells to die and helps cut off the blood supply to tumors. Also prevents cancer cells from making new DNA, st opping their division. In a study published in the 2001 issue of the journal ‘Life Sciences‘ states that green tea catechins can cause the programmed cell death, of prostate cancer cells in the laboratory. Researchers discovered that low doses of COX-2, which has been shown to suppress prostate cancer in animals, combined with EGCG (Epigallocatechin gallate) slowed the growth of prostate cancer cells by suppressing cancer promoting proteins. 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% reduced risk of prostate cancer compared, to those drinking the least . In a study published in the December 2004 issue 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 a double-blind, placebo-controlled study, 60 men took 200 mg of catechin or a placebo three times daily for 1 year. At the end of the study, fewer prostate cancers were detected in the catechin group (1 cancer in 30 men) compared with the placebo group (9 cancers in 30 men).
Results from several animal and human studies suggest that one of the polyphenols in green tea, may help treat viral hepatitis, an inflammation of the liver. Experts at the University of California at Los Angeles (UCLA) have discovered that naringenin and catechin, display powerful antiviral activity on tissue culture infected with hepatitis C. Even after a patient receives a liver from a donor not infected with HCV, the virus in the transplant recipient lingers in the blood and in nearly all cases begins attacking the new organ almost immediately. EGCG disrupted the initial step of Hepatitis C cell entry by interfering with the viral attachment to the cell. 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.
Daily intake of green tea catechins efficiently protects the brain from irreversible damage due to cerebral ischemia, and consequent neurologic deficits. In a experiment, published in the September 2010 ‘Journal of Clinical Neuroscience‘ lab mice with Parkinson’s disease were given EGCG 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. Beta-amyloid plaques are considered to be a major factor of the brain cell death and tissue loss seen in Alzheimer’s disease. Scientists in Taiwan, found that EGCG helps to lower monoamine oxidase type B, (MAO-B), in certain brain tissues. MAO is responsible for breaking down neurotransmitters in the brain, like dopamine, epinephrine, norepinephrine and serotonin.
EGCG prevents heart muscle damage by blocking the activation of inflammation-related compounds that play a critical role in promoting the oxidative damage that kills heart cells in reperfusion injury. A study that followed 8,500 Japanese men and women for 12 years found that men who drank at least 4 cups /day of green tea had a risk of death from coronary heart disease that was only 58 percent that of men who drank 1.3 cups/day or less. Green tea 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 published in the journal.