Studies have revealed that polyphenols in green tea prevent the formation and also the development of tumors anywhere in the body of animals. Tests have been conducted on animal organs to check the beneficial effect of green tea on lung, skin, esophagus, oral cavity, intestine, stomach, liver, colon, mammary gland, bladder, prostrate and pancreatic cancer and tumors. Green Tea helps to promote apoptosis, modulates signal transduction and supresses cell proliferation. In addition to all this epigallocatechin-3-gallat which are green tea polyphenols prevent cell invasion, metastasis and angiogenesis. Thus, a lot of research work is being done to understand the relationship between cancer risk in human beings and consumption of green tea.
Green tea which is a very popular beverage these days and is recommeneded by everyone from doctors to gym instructors because of its health benefits. This is primarily because of catechins present in such tea. The commonly found catchings in green tea are:
The polyphenolic structure of green tea allows delocalization of electrons. This allows high reactivity which allows quenching of free radicals. Various preparations of green tea react with singlet oxygen, superoxide radical, peroxynitrite, peroxyl radical and hydroxyl radical which are reactive oxygen species (ROS). It is believed that among the various catechins present in tea, epigallocatechin-3-gallat (EGCG) is the most capable of reacting with almost all ROS. In addition to this ability these catechins in green tea are effective metal ion chelators. Free metal ion chelation deters the auto-oxidation of various compounds to form ROS.
While studying cell lines, it has been found that catechins in green tea affect many metabolic and signalling patheways which lead to the formation of tumors. These molecular movements may result in inhibition of growth of cancer cells, apoptosis, angiogenesis, metastasis and also inhibit invasion. However, all these activities of cancer prevention is studied by testing on animals only as it cannot be consistently studied on humans. The main reason for this may be lower consumption of tea by certain population of humans. Another thing that needs to be studied very carefully is agents whose systematic bioavailabilty is low. This is because it is necessary to understand cancer and tumor preventive actions performed by them when they come in direct contact with the digetive tract. This may also be applicable to activities of polyphenols and epigallocatechin-3-gallat (EGCG) in other beverages and food.