Chinese Tea Anti-cancer properties
The health effects of tea have been examined ever since the first infusions of Camellia sinensis about 4700 years ago in China. The legendary emperor Shennong claimed in The Divine Farmer's Herb-Root Classic that Camellia sinensis infusions were useful for treating conditions including tumors, abscesses, bladder ailments, and lethargy.
How might tea help prevent cancer?
Among their many biological activities, the predominant polyphenols in green tea―EGCG, EGC, ECG, and EC―and the theaflavins and thearubigins in black teas have antioxidant activity. These chemicals, especially EGCG and ECG, have substantial free radical scavenging activity and may protect cells from DNA damage caused by reactive oxygen species. Tea polyphenols have also been shown to inhibit tumor cell proliferation and induce apoptosis in laboratory and animal studies. In other laboratory and animal studies, tea catechins have been shown to inhibit angiogenesis and tumor cell invasiveness. In addition, tea polyphenols may protect against damage caused by ultraviolet (UV) B radiation, and they may modulate immune system function. Furthermore, green teas have been shown to activate detoxification enzymes, such as glutathione S-transferase and quinone reductase, that may help protect against tumor development. Although many of the potential beneficial effects of tea have been attributed to the strong antioxidant activity of tea polyphenols, the precise mechanism by which tea might help prevent cancer has not been established.
Green tea and cancer prevention
Extracts of green tea and green tea polyphenols have exhibited inhibitory effects against the formation and development of tumors at different organ sites in animals. These include animal models for skin, lung, oral cavity, esophagus, stomach, intestine, colon, liver, pancreas, bladder, mammary gland, and prostate cancers. In addition to suppressing cell proliferation, promoting apoptosis, and modulating signaling transduction, green tea polyphenols, especially (-)-epigallocatechin-3-gallate, also inhibit cell invasion, angiogenesis, and metastasis. This article reviews data on the cancer preventive activities of green tea polyphenols, possible mechanisms involved, and the relationship between green tea consumption and human cancer risk.
[sources: NCBI, National Cancer Institute, Wikipedia]