Green tea has been extensively researched for its health effects in humans. Of all the foods with suspected health effects green tea has been possibly researched the most. Historical and anecdotal evidence suggest tea is beneficial to health. Cell culture, animals, and humans clinical trials and epidemiological research suggest that green tea is has important cellular and biochemical effects in animals. One of the main reasons for the health effects of tea may be the antioxidant effects it possesses. This relates to the presence of a high concentration of polyphenolic compounds in tea leaves. These seep into the water during brewing, and are then absorbed from the gastrointestinal tract following consumption. Accumulation of the catechins, a group of polyphenols belonging to the flavonoid class of phytonutrients, in tissues, has been suggested to be one of the reasons for the health effects of green tea. Catechins protect the tissues they accumulate in, and this provides a significant reduction in total oxidative stress.
Reducing oxidative stress is beneficial because it is now thought that oxidative stress is a primary driver of disease. Oxidative stress leads to cell dysfunction, and by protecting the cells and tissues, catechins are effective disease preventative agents. Oxidative stress can lead to increases in inflammation, and catechins and other polyphenols in tea may be effective anti-inflammatory agents. This ability to prevent inflammation explains their cardioprotective effects, as inflammation is now thought to contribute to the development of the dysfunction seen in cardiovascular disease. Flavonoids, including catechins may also be effective regulators of gene expression. Although this may result from their ability to regulate cell oxidation levels, they may directly affect gene regulation in other ways. One result of the ability to regulate gene expression may be an apoptotic effect of green tea catechins on cancer cells. This apoptotic effect may explain the anti-cancer effects of tea drinking.
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