Tea And EGCG Effects On Cataracts by Green Tea Health News
Tea and EGCG may reduce risk of developing
cataracts
Cataracts, a clouding of the lens of the eye, is one of the
primary causes of blindness in the world. Approximately half of all
Americans over age 65 have cataracts (CDC).
While sunlight, smoking, diabetes, and steroid use can
contribute to early development of cataracts, most cataracts are
associated with aging.
Over the last decade, researchers have begun to study the
effects of black tea, green tea, and EGCG from green tea extract on
preventing the development of cataracts in the lens of the eye.
The cloudy vision from cataract lens opacity is associated with
oxidative stress. Free radicals (singlet oxygen molecules) damage
cells including the retina and lens of the eye. Much cataract
research has concentrated on the protective effect of antioxidants
like vitamin E, and special antioxidant chemicals from tea and EGCG
(green tea) to stop the free radical damage.
- an animal study found significant cataract reduction when
green tea extract was given for several days before and after the
start of cataracts (Gupta SK, Green tea (Camellia sinensis)
protects against selenite-induced oxidative stress in experimental
cataractogenesis, Opthlamic Research, July 2002)
- both green and black tea given to rats slowed the progression
of cataract development (Thiagarajan G, Antioxidant properties of
green and black tea, and their potential ability to retard the
progression of eye lens cataract, Experimental Eye Research,
September 2001)
- a case-control study with cataract patients in India found
that cataract patients had significantly lower nutritional intakes
of tea, green leafy vegetables, fruit, and micronutrients, while
also showing significantly higher intakes of animal products and
fried foods
- cell studies of EGCG found that the strong antioxidant
capacity of epigallocatechin gallate (EGCG from green tea)
protected eye lens cells from apoptotic death from free radicals by
modulating capsases, Bcl-2 family, MAPK, and Akt pathways
Ultraviolet light frequencies also create free radicals in the lens
of the eye. One study found that caffeine prevented many chemical
reactions to UV light that damaged the eye. This may explain why
both high antioxidant green tea and EGCG, and black tea with higher
caffeine levels have shown protective effects.
Diabetes is expected to reach epidemic proportions in the world
within a few decades. Along with life-threatening damage, diabetes
also can increase the risk of permanent damage to the eyes,
including speeding up cataract formation.
- an animal study using a model for diabetes found that both
green and black tea given daily caused significant reductions in
cataract formation as well as reducing high blood sugar (Vinson JA,
Black and green teas equally inhibit diabetic cataracts in a
streptozotocin-induced rat model of diabetes, Journal of
Agricultural and Food Chemistry, May 2005) - several studies
pairing vanadate to lower blood sugar with Lichee black tea extract
to reduce diarrhea (a side effect of vanadate medication for
diabetics) found complete prevention of cataracts in an animal
diabetic model (Clark TA, Codelivery of a tea extract prevents
morbidity and mortality associated with oral vanadate therapy in
streptozotocin-induced diabetic rats, Metabolism, September
2004)
In industrialized countries, loss of vision due to cataracts can
usually be restored with cataract surgery. In other areas,
encouraging inexpensive antioxidant nutrients like daily tea and
EGCG green tea may reduce the burden of cataract vision loss on the
communities.
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