All teas (white, green, black, oolong, and others) are ultimately derived from the same plant, Camellia sinensis. Differences between teas generally relate to the way the plant is grown and the method of leaf preparation. Green and white tea, unlike black and oolong tea, are not fermented, so many of the plant's active constituents remain intact.

Green tea extract is rich source of catechins, a class of bioflavonoid compounds with strong antioxidant potential. Green tea catechins with the highest antioxidant activity are epigallocatechin-3-gallate, epicatechin-3-gallate, epigallocatechin and epicatechin.

Green tea extract demonstrates antimutagenic potential against a variety of mutagens (mutation-causing agents). Studies investigating this potential have suggested that green tea may be protective against a variety of cancers.

In some Chinese populations, consumption of green tea amounts to several cups per day. No evidence of toxicity has been observed.