All kinds of tea are rich in naturally occurring flavonoids, which have strong anti-oxidant properties. There is also growing evidence that anti-oxidant rich foods may aid in reducing the risk of some cancers and cardiovascular disease. The anti-oxidant catechin in green tea is converted to theaflavins in black tea as the tea is processed, however both anti-oxidants are quite healthful. But for this reason, green and white tea are considered richer sources of anti-oxidants by some, as their being minimally processed retains a larger portion of the flavonoids naturally present in the leaves.