Anti cancer function

Numerous studies suggest that green tea protects against a range of cancers, including lung, prostate and breast cancer. The reason cited is the antioxidant epigallo catechin gallate (EGCG), according to Hirofumi Tachibana's team at Kyushu University in Japan. Their research showed that growth of human lung cancer cells that have a cell receptor called 67 LR is slowed significantly after drinking just two or three cups of green tea, which contains EGCG. The research also showed that 67 LR is involved in the propagation of prion diseases such as mad cow disease in humans. So knowledge of EGCG's effect on 67 LR might have implications in the treatment of these diseases.

According to the U.S. National Cancer Institute, in laboratory studies using animals, catechins inactivated oxidants before cell damage occurred, reduced the number and size of tumors, and inhibited the growth of cancer cells

Anti diabetes function

There is also epidemiological evidence that drinking green tea  may help prevent diabetes although it is worth noting that this is evidence of an association, but that prospective studies are needed to confirm the effect.

Lowers stress hormone levels

According to a study by UCL researchers published in the journal Psychopharmacology, drinking black tea has an effect on stress hormone levels in the body and thus helps in recovering more quickly from life's stresses. The study showed that, 50 minutes after a high stress event, subjects who drank 4 cups of black tea per day for a 4 week period experienced an average cortisol drop of 47%, compared to 27% for the placebo group. Blood platelet activation, which is linked to blood clotting and the risk of heart attacks was also lower in the tea drinker's group