There are many classifications of tea, which are generally divided into black tea, green tea, oolong tea, white tea, scented tea, black tea and reprocessed tea according to technology and tea quality. There are many nutrients in tea, but in view of the very small daily consumption and the limited proportion of many nutrients dissolved in water, it has little contribution to human health. In the aspect of health care function, non-nutritive substances mainly play a role, including polyphenols, pigments, theanine, alkaloids and aromatic substances, etc., with polyphenols playing the most important role.

Polyphenols in tea mainly include catechins, flavonoids and flavonoid glycosides, anthocyanins, etc. These substances are collectively called phytochemicals, also called phytochemicals, which are a large class of substances with antioxidant, anti-aging and tumor prevention.

According to animal medicine and epidemiological investigation, tea has anti-cancer and anti-cancer effects. An Italian scientific study has proved that tea has a preventive effect on human oral cancer and pharyngeal cancer. Among these preventive effects on cancer, green tea is particularly effective. According to Chinese research, drinking green tea often can reduce the incidence of esophageal cancer by 50%, the risk of pancreatic cancer and rectal cancer by 40%, the risk of gastric cancer by 20-30% and colon cancer by 20%. Not only that, but also research reports that drinking all kinds of tea can reduce the oxidative damage and DNA damage caused by smoking. It seems that tea plays an important role in the prevention of human cancer.