①It's known that green tea is a symbol of Chinese culture. Also, it helps to improve health in so many ways that some people think of it as a kind of medicine. Perhaps that is why the Chinese have been using it for more than 4, 000 years to treat all kinds of medical problems. Today, scientists know that there are catechin, caffeine, vitamin C and theanine in green tea that are good for health.

②Catechin is helpful for lowering (降低) cancer (癌症) risk. It protects the body from cancer-causing substances ( 物 质 ) and slows the growth of cancer. Besides fighting cancer, catechin prevents serious health problems like heart disease. 

③Caffeine causes the heart to beat faster. That's why it was once thought that caffeine was not very healthy, but studies suggest that there are also good reasons for drinking caffeine. Specifically, caffeine has to do with a lower risk for Parkinson's disease and liver ( 肝 脏 ) disease. Yet, caffeine also has some weaknesses. It can influence sleep and make people nervous, so experts advise teenagers not to have more than 100 ml of caffeine a day. This is about the caffeine of a small cup of coffee.

④Vitamin C is something that the human body cannot make enough by itself. So we have to get it through food and drink. The vitamin may play a role in improving physical conditions to colds and the flu. Also, it helps people to get well more quickly from those illnesses. 

⑤Theanine is another healthy substance found in tea. It has been shown to lower stress, both mental and physical, and increase mind abilities. It is also used for preventing some brain diseases. 

⑥As you can see, green tea has many good values. Drinking it may help you stay healthy. Of course, as with any healthy substance, it is important to check if there are any bad influence as well.