I was reading at the link below the benefits of polyphenols which are contained in most teas...
http://www.healthcastle.com/tea.shtml
http://www.healthcastle.com/tea.shtml
At the bottom of the page concerning decaf tea it states...Numerous studies have demonstrated the anti-cancer properties of polyphenols. Some studies indeed suggested that tea's polyphenols may reduce risk of gastric, esophageal and skin cancers if one consumes 4 to 6 cups daily. Other laboratory studies have found that polyphenols help prevent blood clotting and lower cholesterol levels. A recent study published in December 2005 showed that just 2 cups of tea may lower the risk of ovarian cancer by 46 percent in women.
So it is possible that decaf tea may have the polyphenols removed. If polyphenols are removed from decaf tea, are there any benefits in drinking decaf tea over tea which is not decaf?We do not know whether decaf teas have the same polyphenols, and thus the same health benefits. It is not yet known if removing caffeine also removes polyphenols in the decaffeinating process.