Yesterday we reported on new evidence supporting the claim that the antioxidant properties of tea can be good for maintaining blood flow, but research presented at the same Nutrition Week conference shows that these properties vary greatly between types of tea.
An analysis of 20 common brands by Susanne M. Henning, a researcher at the University of California Los Angeles Center for Human Nutrition, showed wide variation from one brew to another.Henning measured the amounts of catechins, one of the antioxidant polyphenols found in tea, in a variety of green and black teas available in the US. Each was brewed for around three minutes.
Henning's team found levels as high as 217mg for Celestial Seasonings Green Tea, 201mg for Lipton Green Tea, 164mg for Bigelow Darjeeling Blend (black tea) and 157mg for Uncle Lee's Green Tea. At the other end of the scale, Stash Premium Green Tea Decaf contained just 53mg, Twinings Earl Grey Black Tea had just 46mg, Bigelow Constant Comment (black tea) contained 38mg and Bigelow Constant Comment Decaf had just 10mg.
An additional study of two iced tea brands, Lipton Lemon Iced Tea and Snapple Peach Iced Tea, showed that they had no measurable catechin content at all.
Henning said the study raised the question of whether companies should label the antioxidant content of their teas. "I think it would be good if they would," she said, particularly since some companies promote their products as containing antioxidants.
Black and green tea are derived from the same plant but are processed in different ways, which may account for some of the differences in antioxidant levels. Green tea is commonly thought to have more antioxidants than black tea, and this was partially borne out in Henning's study. However, since Henning's research focused only on catechins and not on all the antioxidants found in tea, further research will be necessary before a definitive claim can be made about which teas are best.