TEA IN CHEMOPREVENTION OF CANCER - EPIDEMIOLOGIC AND EXPERIMENTAL STUDIES (REVIEW)

This review summarizes available information on epidemiological and ex perimental data showing an association of tea consumption with cancer prevention. Studies showing cancer risk associated with tea consumptio n are also summarized. Tea is grown in about 30 countries and, next to water, is the most widely consumed beverage in the world. Experimenta l studies demonstrating the chemopreventive effects of tea have been c onducted principally with green tea; limited studies have also assesse d the usefulness of black tea. Majority of these studies have been car ried out in skin tumor model system where consumption through drinking water of water extracts of tea or a polyphenolic fraction isolated fr om tea has been shown to afford protection against chemical carcinogen - or ultraviolet radiation-induced skin tumorigenesis. Tea consumption has also been shown to afford protection against chemical carcinogen- induced lung, forestomach, esophagus, duodenum, pancreas, liver, breas t and colon carcinogenesis in specific bioassay models. Evidence has a lso accumulated showing that tea polyphenols prevent tumor promoter- a nd ultraviolet B-induced inflammatory responses in murine skin. The sp ecies and strains of animals, dose, route, frequency and duration of c arcinogen administration, as well as types, route of administration an d duration of tea or its polyphenolic component(s) treatment are descr ibed in detail. A brief description regarding mechanism(s) responsible for the broad chemopreventive effects of tea is provided. Epidemiolog ic studies, though inconclusive, in general suggest a possible prevent ive effect of tea consumption on human cancer. On the basis of availab le information, epidemiologic and experimental studies are ongoing to draw the possible relationship between tea consumption and cancer caus ation and prevention. Appropriate strategies for future clinical chemo prevention trials to translate animal data to human cancer risk are wa rranted.