Tea polyphenols are chemical compounds, such as flavanoids and tannins, found naturally in tea. Depending on how the tea is harvested, handled, processed, and brewed, the polyphenol level can vary. These chemical compounds are believed to be beneficial to human health, and they are the basis of many claims made about the health benefits of tea. As with many natural compounds that appear to have health benefits, it is difficult to isolate and study these polyphenols on their own, and some researchers have suggested that their actions in the body may actually be the result of several compounds working together.
Polyphenols are antioxidants, which means that they can reduce the risk of developing coronary artery disease and a number of other health problems. The compounds found in tea have also been linked with cancer reduction, as they appear to block the action of some enzymes linked with this condition. Because cancer is so complex and it can be influenced by many environmental and genetic factors, scientists are reluctant to say that tea polyphenols will categorically prevent cancer, although rates do seem to be lower in tea drinkers after controls for other obvious factors like diet are used to evaluate the data.
The polyphenols found in tea also appear to suppress the growth of harmful bacteria, while promoting beneficial bacteria in the gut. The Chinese tradition of drinking tea with and after many meals may be linked to this activity, as food can be a prime source of bacterial infection when it is not handled well, and drinking tea with food could reduce the risk of developing infections.
The flavor of tea is also influenced by its polyphenols. Tannins, found in high concentrations in black tea and lower concentrations in green and white tea, lend tea its distinctive dark color and bitter, sharp flavor. Other polyphenols can also change the color of the tea, making it more reddish or brown depending on how it is handled, and the subtle and distinctive flavors of well-processed teas are due in part to these compounds.
The chemicals identified as being present in tea can also be found in other plants. Grapes are another excellent source of these antioxidant chemicals, as are bright fruits and vegetables. Eating a diet rich in plant material confers a number of health benefits, including the benefits of polyphenols.