For thousands of years, green tea has been popular throughout Asia for its pleasant, soothing taste and time-honored health benefits. Practitioners of traditional Chinese medicine have recommended green tea since 3000 BC, and green tea is still an important part of the Chinese material medica.
Modern studies confirm the efficacy of green tea for preventing and treating diseases and other health conditions. Green tea gets its health-promoting properties from phytochemicals known as polyphenols. Polyphenols are bitter, astringent phytochemicals that constitute 15 to 30 percent of dried green tea leaves by weight.
Although black tea is made from the same plant as green tea, it does not provide the same health benefits. Black tea leaves are fermented, a process that destroys polyphenols. Green tea leaves are lightly steamed, a process that protects polyphenols by destroying the enzyme that oxidizes them.
The polyphenols in fresh tea leaves are catechins, including gallocatechin (GC), epigallocatechin (EGC), epicatechin (EC), epigallocatechin gallate (EGCG) and epicatechin gallate (ECG). Catechins promote health in the following ways:
Combating oxidative stress
Protecting against cancer
Lowering cholesterol levels
Reducing blood pressure
Fighting bacteria and viruses
Protecting cognitive function
Combating Oxidative Stress
Oxygen is essential for human life, but oxygen metabolism creates harmful by-products known as free radicals. Free radicals are unstable molecules that attack cells in the body, destroying cell membranes, damaging DNA and oxidizing lipids. These cellular assaults can contribute to cancer, heart disease and other serious health conditions. Our bodies protect themselves against free radicals with the help of antioxidants, which can be found in foods such as fresh fruits and vegetables – and green tea.
Studies demonstrate that the polyphenols in green tea efficiently scavenge free radicals and are more powerful than vitamins C and E, two well-known antioxidants. These polyphenols are particularly important in preventing lipid peroxidation, a process that plays a key role in the buildup of arterial plaque. Green tea also increases the activity of the body’s own antioxidant system, including the activation of powerful natural antioxidants like superoxide dismutase and glutathione peroxidase.