Green tea contains compounds known as antioxidants, which help neutralize free radicals. Free radicals may sometimes exert harmful effects upon cells and are said to be involved in the initiation of certain types of cancers. The compounds known as polyphenols belong to this group of plant antioxidants, and have been shown to inhibit human carcinogens of diverse origin in laboratory studies. Research in animals fed green tea seems to confirm this, although not all studies have shown the same effects. It is thought that this herb’s antioxidant effect could be of use as a preventive to some types of cancers, namely prostate, ovarian, breast and colon cancer, although the mechanism by which it would exert this effect is only partially understood at this time. Much more research in humans is needed in order to confirm all of green tea’s potential benefits as a cancer preventive. This herb has diuretic properties, encouraging urination. It has also been used in China as a tonic for people with weak hearts. This herbal products used for weight loss contain green tea, purportedly because it increases “thermogenesis”, or an increase in temperature that is supposed to break down fat in the body. Since green tea contains caffeine, it is also ingested as a mild stimulant to combat fatigue. This herb should not be consumed in large quantities before bedtime in people who have trouble getting to sleep. Green tea may be of help in reducing cholesterol levels, as well as risk for heart attacks, but more research needs to be done in this area.