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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