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Epigallocatechin-3-gallate (EGCG) is a polyphenol that is found in high concentrations in green tea, some dark chocolate, and cocoa. Also known as epigallocatechin gallate, this compound is a type of flavonoid known as a flavonol. It has been widely studied in animals and humans for its health effects. There is good evidence that consumption of dietary epigallocatechin-3-gallate helps prevent cardiovascular disease and lowers the rate of cancer.
There are a number of health benefits associated with epigallocatechin-3-gallate. For instance, it has been shown to have a protective effect against cardiovascular disease. Also an antioxidant, this compound has been highly studied for its anti-cancer effects. In addition, it has been found to be an antibiotic, and to be able to decrease the amount of fatal sepsis in rodents. EGCG also shows promise for improving glucose tolerance in rodents with diabetes, and is being studied to determine if it can help control Type II diabetes in humans.
Flavonoids are a subtype of polyphenols, and contain various types of compounds. Flavonols are a class of flavonoids typified by catechins, which include epicatechin and catechin. Epigallocatechin has the basic structure of epicatechin, but contains an additional hydroxyl—OH—group. Some molecules have a gallic acid group attached to them by an ester linkage. This generates the compound epigallocatechin-3-gallate, which is also technically a catechin.
Catechins compose approximately 25% of the weight of dried tea leaves, and are known as green tea phenols. They are often studied for their effects on human health. The most common catechin in tea is epigallocatechin-3-gallate. It is much more prevalent in green tea, because most of it is destroyed during the fermentation process involved in generating black tea. Also present in green tea are epicatechin, epicatechin gallate, and epigallocatechin.
Green tea is an excellent source of EGCG and the other catechins. One should be aware that adding milk to the tea can destroy the effects of the phenolics, however. This does not appear to be the case for the phenolics in coffee.
The human diet also contains catechins in many types of fruits and vegetables, as well as wine. Cocoa is another source of catechins. Some dark chocolate can be a good source, although sometimes the substance is removed because it can be a source of bitterness. The chocolate label does not always reflect this deficiency.
Supplements of green tea extract are available. As with all supplements, however, one should consult a doctor before taking them. Preliminary research has shown that young women who consumed green tea extract with meals had a subsequent depletion of iron.