Green Tea Compounds Fight Glaucoma, Other Eye Diseases

Green Tea Compounds Fight Glaucoma, Other Eye Diseases by Deborah Mitchell

For the first time, scientists have confirmed how certain healthful compounds in green tea are indeed absorbed by the lens, retina, and other eye tissues. This increases the possibility that green tea may prevent development of glaucoma and other eye diseases.

This discovery is significant because until now, researchers did not know whether the potent antioxidants in green tea called catechins were capable of reaching the tissues in the eye, even though many have long felt that catechins are important in protecting the eyes against various diseases. This new study shows that catechins do make the journey from the stomach and gastrointestinal tract into the tissues of the eye.

Catechins, which include gallocatechin (GC), epigallocatechin gallate (EGCG), and epicatechin gallate (ECG), among others, have the ability to fight free radicals and reactive oxygen species which damage cells through a process called oxidative stress. Photo-oxidative stress can initiate the formation of cataracts, and oxidation is also associated with primary open angle glaucoma and retinopathy in preterm neonates.

In this study, Chi Pui Pang and colleagues administered green tea extract to 11 groups of rats, six animals per group. After administering the extract, the animals were sacrificed at different times, ranging from immediately after receiving the extract up to 20 hours later. The eye tissues in all the rats were examined, and the researchers found that eye tissues absorbed significant amounts of individual catechins. The ability of green tea catechins to reduce damaging oxidative stress in the eye lasted for up to 20 hours.

Glaucoma affects more than 4 million Americans, and is responsible for blindness in approximately 120,000 people in the United States. The American Academy of Ophthalmology reports that nearly 22 million Americans 40 years and older have cataracts. Another 10 million Americans have age-related macular degeneration, which is the leading cause of severe vision loss in people age 60 and older.

Several other antioxidants have been studied for their ability to protect the eye against oxidative stress and eye diseases such as glaucoma and cataracts. Studies using these antioxidants, including vitamins C and E, lutein, and zeaxanthin, have not yielded consistent results. This study's authors note that to the best of their knowledge, theirs is the first paper that shows how individual catechins are distributed once green tea extract is ingested and the first to evaluate their antioxidative effects in different parts of the eye. The report concludes that "Our results indicate that green tea consumption could benefit the eye against oxidative stress."

SOURCES:
American Academy of Ophthalmology
Chu KO et al Journal of Agriculture and Food Chemistry 2010 Jan 19; 58(3): 1523-34
Glaucoma Research Foundation

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