Polyphenol: A kind of chemical that (at least in theory) may protect against some common health problems and possibly certain effects of aging.
Polyphenols act as antioxidants. They protect cells and body chemicals against damage caused by free radicals, reactive atoms that contribute to tissue damage in the body. For example, when low-density lipoprotein (LDL) cholesterol is oxidized, it can become glued to arteries and cause coronary heart disease.
Polyphenols can also block the action of enzymes that cancers need for growth and they can deactivate substances that promote the growth of cancers. The polyphenol most strongly associated with cancer prevention is epigallocatechin-3-gallate, or EGCG.
All tea contains polyphenols. Teas and polyphenols isolated from tea have been shown in the laboratory to act as scavengers of oxygen and nitrogen-free radicals, protecting the fatty membranes of cells, proteins and DNA. However, the results of human studies of tea and polyphenols to date (2001) have been inconsistent and have yet to prove anything one way or the other as regards the value of polyphenols.