Tea leaves come from the top leaves of the plant called Camellia sinensis.These leaves contain a chief powerful antioxidant product called pigallocatechin gallate (EGCg), and small amounts of various catechins (predominant in green tea). All these are polyphenols, chemicals which have been proven to inhibit the growth of tumors and help prevent the spread of cancer. The fresh tea leaves likewise contain an enzyme, polyphenol oxidase. When the freshly harvested leaves are processed with steam or heated up in a pan, the polyphenol oxidase becomes inactivated. Green tea is made from drying the heated leaves followed by rolling and chopping. If upon harvesting and chopping to free the polyphenol oxidase the leaves are set aside to stand at about 40Â°C for 30 minutes, a partial biochemical oxidation of the polyphenols happens which results as oolong tea, preferred in southern China and Southeast Asia. Letting the oxidation to continue for 60â€“90 minutes converts the polyphenols to those distinctive of black tea, such as thearubigins and theaflavins.
Elaborate research shows that these antioxidant polyphenols from green, oolong, or black tea have almost the same beneficial effects. For instance, they decrease the oxidation of LDLcholesterol, a risk factor for coronary heart disease. The antioxidants also lessen the oxidation of DNA, resultant to the action of carcinogens and to the peroxidation responses on lipids, yielding oxy radicals and peroxides. Additionally, they can stimulate enzymes in tissues such as liver that assist in detoxifying harmful chemicals, including carcinogens, and reduce the risk of advancing chemicals in the total cancer process. Tea polyphenols also diminish the rate of cell gemination, particularly of abnormal, transformed cells involved in the development of cancer. This attribute slows the development of early cancer cells and may even be beneficial as auxiliary therapy of neoplasia. There are also several indications that regular intake of tea changes the intestinal bacterial flora, encouraging the growth of good bacteria and getting rid of those with potentially harmful properties. Clearly, tea is an inexpensive drink, that is easily prepared, hot or cold, which is also a pleasant and flavorful. It can also be consumed plain or with some milk, honey, or lemon. It is aseptic regardless of the quality of drinking water used, because boiling is the accustomed way of preparing it.
The scientific advancement in the discovery of the benefits of tea has been noteworthy in the recent past decades. These developments have been recorded in several scientific publications, critiques, and presentations at symposia and conferences.
Dr. Yukihiko Hara one of the world's experts on the multiple health aspects of tea has written a detailed explanation on the numerous facets of tea production, its innate properties and components, analysis, chemical and biochemical functions, processes in reducing the risk of heart diseases and cancers. In his book Green Tea: Health Benefits and Applications he particularly emphasized the important health benefits acquired through the oral consumption of tea catechins.