Green Tea Compounds May Boost Eye Health
Lee Swanson Research Update
Researchers from the Chinese University of Hong Kong report that catechins from tea could be detected in significant amounts in various eye structures. According to the findings, published in the Journal of Agricultural and Food Chemistry, the retina of rats absorbed the highest levels of gallocatechin, while the aqueous humor tended to absorb epigallocatechin.
Furthermore, the potential beneficial effects of green tea catechins in reducing harmful oxidative stress were sustained for up to 20 hours.
"Although many antioxidants have been studied in the eye, to the best of our knowledge this is the first paper to show distribution of individual catechins after ingestion of green tea extract and to evaluate their in vivo antioxidative effects in various parts of the mammalian eye," the new study reported.
Green tea contains between 30% and 40% of water-extractable polyphenols, while black tea (green tea that has been oxidized by fermentation) contains between three percent and ten percent. The four primary polyphenols found in fresh tea leaves are epigallocatechin gallate (EGCG), epigallocatechin, epicatechin gallate and epicatechin.
Chi Pui Pang and colleagues fed laboratory rats green tea and subsequently analyzed the eye tissues. Catechins were indeed observed in the eye tissues, the researchers said.
"Many studies on the oxidative effect of green tea focused on EGCG," the researchers reported. "However, in this study, we found its tissue level was not high. Gallocatechin, epigallocatechin, catechin and epicatechin, on the other hand, sustained high levels in many compartments.
"Although these compounds have a reducing power similar to or lower than that of EGCG, use of a mixture, such as green tea extract, was better than use of a single catechin because of lower cost and synergic effects on antioxidation and bioavailability," they added.
"Our results indicate that green tea consumption could benefit the eye against oxidative stress," the researchers concluded.
Journal of Agricultural and Food Chemistry 58(3):1523-1534, 2010
March 2010
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