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GREEN TEA SHOP>>GREEN
TEA HEALTH>>GREEN
TEA INFORMATION>>Green
Tea, Cancer, and Health
| Green Tea, Cancer, and Health |
By Shutsung Liao
The Ben May institute for Cancer Research and the Department of
Biochemistry and Molecular Biology, University of Chicago
According to Zen Buddhist legend, the first patriarch,
Bodhidharma, around the sixth-century A. D., trying to keep
himself awake, cut off his eyelids. After falling to the ground,
they grew up as tea plants. Ever since, tea has been used to
fend off sleep and clear the soul. Historians believe that tea
originated about five thousand years ago in The Pamirs between
Lndia and China. In Tibet, it is still possible to find tea
trees more than a thousand years old and 100 feet tall.
Commercial tea trees (Camellia senesis) are trimmed often, and
so are small bushy plants about 2-3 feet high. Tea leaves are
picked 3-4 times between spring and fall every year. Green tea
is produced from the leaves that are picked and heated quickly
in a pan or by hot steam to kill microorganisms and stop
enzymatic action to prevent fermentation. Other tea products are
normally fermented to enhance taste and flavor. Oolong tea,
often served in Chinese restaurants, is 25-50% fermented,
whereas black or red teas are over 80% fermented.
In oriental culture, it has been widely believed for a long time
that tea has medicinal efficacy in preventing and treatment of
many diseases. Drinking tea is often related to longevity.
According to Chinese history, Emperor Sin-N on found, more than
three thousand years ago, that a daily cup of tea could dissolve
many poisons in the body. Scientific and medical evaluation of
tea, however, started only very recently. Early epidemiological
studies yielded inconclusive evidence whether tea is medically
beneficial. In fact, some reports warned that consumption of tea
may by linked to cancer of the esophagus and stomach. These
observations have not been confirmed in other studies. Part of
the difficulty in making a clear evaluation of links between tea
and health lie in the use of different varieties of tea products
and confounding roles of other dietary and non dietary
components. An increase in esophageal cancer due to drinking tea
has been positively related to the high temperature of the tea
rather the components of tea.
Recently, numerous scientific studies support a preventive role
for tea in cancer. Epidemiological studies linked green tea use
to a lower rate of esophageal cancer. In Japan, stomach cancer
incidence in tea growing districts is about one half of that in
districts not producing tea. In experimental animals, the
incidence of cancer induced by various chemical
carcinogens(including some of the carcinogens in cigarette
smoke) in different organs(skin, stomach, liver, lung, breast,
duodenum, and colon) can be significantly reduced by allowing
animals to ingest green tea. Rats given green tea for several
months developed less skin cancer when they were irradiated by
ultra violet light. Other human and animal studies, yet to be
confirmed, indicated that long-term use of green tea may reduce
the cholesterol level and increase the high density lipoprotein
(HDL) cholesterol level in blood. One Japanese report also
indicated that the incidence of stroke was 2-3 times lower in
those who drank larger quantities of green tea. Components of
green tea also have anti-inflammatory effects and anti-bacterial
activity, suggesting their possible use in skin care and
prevention of dental caries.
Understanding the molecular mechanism of carcinogenesis may
provide a rational judgment of how green tea components may be
beneficial in prevention and therapy of cancer and other
diseases. Two major components of green tea are epicatechin
gallate (ECG) and epigallocatechin gallate (EGCG) which
represents about 30% of the dry weight of a hot water extract of
green tea. EGCG appears to be the major anti-tumorigenic
substance in green tea. There are indications that these green
tea compounds can interfere with tumor promotion by TPA (a
phobol ester tumor promoter) in carcinogen-induced tumors. Other
studies have indicated that some oncogene functions may be
altered.
We have found that both ECG and EGCG can prevent activation of
male hormones which is needed for development of prostate
cancer, benign prostatic hyperplasia, baldness, and acne.
Therefore, these green tea compounds may be effective in
treating some of these male hormone-related abnormalities in
human. In fact, we have shown that the growth of human prostate
tumors in mice can be prevented and actually suppressed by
administration of EGCG. The effect can be observed within 2 to 4
weeks. Similar EGCG-dependent suppression was also found with
human breast tumors growing in mice.
Since ECG and EGCG can by oxidized by air and its
anti-tumorigenic activity destroyed, some care should be
exercised in the storage of tea and making tea beverage.
Following guidelines may be helpful: (a) buy green tea picked
within a year, (b) store tea leaves in a refrigerator, (c)put
2-3 table-spoons of green tea in a small 8-12 oz thermos, *(d)
add hot water to the top of the thermos to exclude air, (e)
cover tight and allow to stand for 20-30 minutes, (f) pour the
drink into a cup and add a small piece of ice, and drink
immediately. Never drink very hot tea and never leave tea on the
table for a long time before drinking. An alter native method,
which is highly recommended, is to make your own green tea
powder in a coffee bean grinder, then put green tea powder into
anything you want to eat or drink, including meat, fish,
sandwiches, hamburgers, pizza, salads, vegetables, soups, juice,
milk, and ice cream. A final note: the amount of caffeine in one
cup of green tea is about one quarter of that in one cup of
coffee so you can limit your consumption of tea to whatever
level allows you to get a good nightˇ¦s rest.
*(1). For daily use, 3-6 grams dried green tea (102 table
spoons) may be appropriate. For serious problems, 15-30 grams
dried green tea (5-10 table spoons) may be needed. Since the
body may gradually adapt to and destroy green tea EGCG, it may
be a good idea to take green tea intermittently, on for 2-3
weeks and off for 1-2 weeks, especially for a heavy douser.
*(2). For updated review, see: S. Liao, Y. H. Kao, and R. A.
Hippakka(2001) ˇ§Green Tea: Biochemical and Biological Basis for
Health and Benefitsˇ¨ in ˇ§Vitamins and Hormonesˇ¨ Volume 26, pages
1-94.
Product information
Recent studies show that EGCG (epigallocatechin gallate), found
in Green Tea, is a key chemical compound that provides numerous
health benefits. Thus, it is essential to consume Green Tea rich
in EGCG.
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