According to the results of a study released in the book “Free Radicals in Food”, the antioxidants in green tea called tannins may help to protect organs and tissues from oxidative damage. Tannins are common antioxidants found in vegetables, and especially fruits, wine and tea. Due to the very minimal levels of oxidation that the tea leaves used for making green tea are exposed to, green tea contains a lot more of these tannins than both oolong and black tea varieties, even though they are made from the leaves of the same plant. This is why we hear a lot about the benefits of green tea, but not so much about the benefits of oolong and black tea – green tea contains the most health-promoting antioxidants.
In this study, researchers Ken M Reidl, Stephane Carando, Helaine M Alessio, Mark McCarthy and Ann E Hagerman tested the effects of a specific tannin, found abundantly in green tea called epigallocatechin gallate (EGCG), upon the tissues of rats. After a 6.5 week long feeding trial the rats were examined for oxidative effects within their tissues after intensive exercise – oxidative effects are multiplied by exercise. It was found that the rats not given green tea displayed signs of oxidative damage within their liver and kidneys, while the liver and kidney tissues of those given green tea were protected.
Of course these results would have to be repeated in human trials to see if these positive effects transfer to human tissues and organs. Although the results of many other studies show that drinking green tea protects DNA and some tissues and can dramatically reduce our risk of developing cancer and heart disease, and increase our longevity.
Ref: Antioxidant Activity of Tannins and Tannin-Protein Complexes: Assessment In Vitro and In Vivo
Riedl, Ken M. ; Carando, Stephane ; Alessio, Helaine M. ; McCarthy, Mark ; Hagerman, Ann E.
Free Radicals in Food. March 4, 2002, 188-200