A beverage brewed from the leaves of the Camellia sinensis tea plant. Green tea contains chemicals called POLYPHENOLS that researchers believe inhibit the uncontrolled growth that characterizesCANCER cells, especially those of cancers of the GASTROINTESTINAL SYSTEM and the prostate. One polyphenol in particular, epigallocatechin gallate (EGCG), is a potent ANTIOXIDANT that is capable of killing PROSTATE CANCER cells grown in research laboratories. Researchers continue to explore how much of this effect manifests in the human body with consumption of EGCG. Green tea is also available as a ground powder in capsules, sold as a nutritional supplement in the United States.