Cancer Preventive Activities of Tea Polyphenols

The cancer preventive activities of tea (Camellia Sinensis Theaceae) have been investigated extensively. Green tea polyphenols have been shown to inhibit tumorigenesis in different animal models, including those for cancers of the lung, oral cavity, esophagus, stomach, small intestine, colon, bladder, liver, pancreas, skin, prostate and mammary glands. Enhancement of apoptosis, suppression of cell proliferation, and inhibition of angiogenesis have been shown to be associated with the inhibition of carcinogenesis by tea polyphenols in animals. Many studies in cell lines have demonstrated the modulation of signal transduction and metabolic pathways by (-)-epigallocatechin-3-gallate (EGCG), the most abundant and active polyphenol in green tea. The cancer preventive activity of green tea in humans, however, has not been conclusively demonstrated in epidemiological studies. The relationship between tea consumption and cancer risk may become more clear if we could better quantify the tea consumption, adjust for confounding factors and consider genetic polymorphisms of the population. Ongoing human studies on the prevention of prostate, oral, lung, colon, and breast cancers by tea polyphenols are expected to yield more information on this important topic.