People have felt for a long time that green tea has positive effects on our health. Recently,many studies have been done to prove these claims. These studies have shown that green tea can reduce heart disease,some kinds of cancer and improve brain functioning. But these studies have only been done on animals. There have also been many studies on green tea's effects of humans. Scientists have studied green tea's effect on weight loss,cancer,heart dlsease, Parkinson's disease and glaucoma. The results of these studies have shown that green tea might help in treating or preventing these diseases. More research needs to be done to prove completely that green tea can or can't help in treating these diseases.