Green tea in chemoprevention of cancer

The concept of prevention of cancer using naturally occurring substances th at could be included in the diet consumed by the human population is gainin g increasing attention. Tea, next to water, is the most popularly consumed beverage in the world and it is grown in about 30 countries. Abundant data, amassed from several laboratories around the world in the last ten years, provided convincing evidence that polyphenolic antioxidants present in tea afford protection against cancer risk in many animal-tumor bioassay systems . The epidemiological studies, though inconclusive, have also suggested tha t the consumption of tea is associated with a lowered risk of cancer. Much of this work has been done on green tea; less is known about black tea. Gre en tea contains many polyphenolic antioxidants, and (-)-epigallocatechin-3- gallate (EGCG) is the key polyphenolic antioxidant believed to be responsib le for most of the cancer chemopreventive properties of green tea. This rev iew will discuss these effects and the molecular mechanisms associated with the biological response to green-tea polyphenols.