New research from Hong Kong suggests that green tea may protect against eye diseases such as glaucoma because the researchers found green tea antioxidants called catechins present in various tissue structures in the eyes of laboratory rats after they had ingested green tea.

The researchers, based at Hong Kong Eye Hospital, Kowloon, and the Prince of Wales Hospital, Shatin, in the New Territories, Hong Kong, have written about their findings in a paper that appeared in the 10th February print issue of the American Chemical Society's bi-weekly Journal of Agricultural and Food Chemistry.

Green tea contains catechins which belong to the family of antioxidants that includes vitamin C, vitamin E, lutein, and zeaxanthin and is well-known for its disease-fighting properties.

Until this study, however, nobody knew if green tea catechins actually passed from the stomach and gastrointestinal tract into the tissues of the eye.

For their investigation Dr Chi Pui Pang, of the Hong Kong Eye Hospital, and colleagues examined the eyes of dead rats that had been fed green tea extract for varying amounts of time.

When they examined the cornea, lens, retina, choroid-sclera, vitreous humor, and aqueous humor, they found evidence that these various eye structures had absorbed singificant amounts of individual catechins.

For example, the retina absorbed the highest levels of gallocatechin and the aqueous humor absorbed epigallocatechin.

They also found that the time of maximum concentration of the catechins varied from 0.5 to 12.2 hours and their effects in reducing harmful oxidative stress in the eye lasted for up to 20 hours after consumption.

Chi Pui Pang and colleagues concluded that:

"Our results indicate that green tea consumption could benefit the eye against oxidative stress."

However, more studies are needed to verify the same effects occur in humans.

"Green Tea Catechins and Their Oxidative Protection in the Rat Eye."
Kai On Chu, Kwok Ping Chan, Chi Chiu Wang, Ching Yan Chu, Wai Ying Li, Kwong Wai Choy, Michael Scott Rogers and Chi Pui Pang.
Journal of Agricultural and Food Chemistry, 10 February 2010, 58 (3), pp 1523-1534.
DOI: 10.1021/jf9032602

Source: American Chemical Society.

Written by: Catharine Paddock, PhD