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.