Green tea catechins for well-being and therapy: prospects and opportunities

Tea is derived from the leaves and buds of Camellia sinensis (Theaceae) plant, and is consumed worldwide. Green tea was discovered in the People's Republic of China approxi- mately 3,000 BC. Lu Yu (733-803) published a book that describes the history of tea, the techniques, and utensils used for manufacturing, the method of preparation, and drinking of tea in the People's Republic of China. Green tea contains various components with specific health- promoting effects and is believed to exert protective effects against diseases such as cancer, obesity, diabetes, hepatitis, and neurodegenerative diseases. Of the various tea components, the polyphenol catechins have been the subject of extensive investigation. Among the catechins, (−)-epigallocatechin gallate has the strongest bioactivity in most cases. Caffeine induces alert- ness, decreases the sensation of fatigue, and has a diuretic effect. Theanine and γ-aminobutyric acid can lower the blood pressure and regulate brain function. Vitamin C exhibits antiscorbutic activity, prevents cataracts, and may boost the immune system. Majority of the scientific evi - dence based on cellular and animal experiments as well as a number of human epidemiological and intervention studies indicate that green tea and (−)-epigallocatechin gallate have beneficial health effects against various diseases. However, conflicting results have also been reported. Since confounding factors could affect the results, future studies should be designed to elimi- nate such factors for better understanding of the benefits of green tea on human health. Genetic and environmental factors such as race, sex, age, and lifestyle may also influence the results of human studies. Although care should be taken to avoid the consumption of green tea and supplements with very high catechin content, recent findings suggest that habitual drinking of green tea promotes longevity.