Green tea may protect against colon cancer by Reuters Health
NEW YORK (Reuters Health) - An extract of green tea wards off
colorectal cancer, animal experiments show.
According to research reported at the Sixth International
Conference on Frontiers in Cancer Prevention, sponsored by the
American Association for Cancer Research, a standardized green tea
polyphenol preparation (Polyphenon E) limits the growth of
colorectal tumors in rats treated with a substance that causes the
"Our findings show that rats fed a diet containing Polyphenon E
are less than half as likely to develop colon cancer," Dr. Hang
Xiao, from the Ernest Mario School of Pharmacy at Rutgers
University, Piscataway, New Jersey, noted in a statement.
These results are consistent with previously published results,
which showed that green tea consumption was associated with lower
colon cancer rates in Shanghai, China, he also noted.
In the study, Xiao and colleagues injected rats with
azoxymethane, a chemical known to produce colorectal tumors that
share many characteristics with colorectal cancer in humans. Then
they fed the animals a high-fat Western-style diet with or
without Polyphenon E for 34 weeks. The amount of Polyphenon the
animals took in was roughly equal to about four to six cups of
green tea per day.
Polyphenon E decreased the total number of tumors per rat and
decreased tumor size, compared with control rats that were not
given Polyphenon E, Xiao told the conference.
"In the control group," he said, "67 percent of rats developed
malignant tumors while in the treated group only 27 percent of rats
had malignant tumors. Most important, tea polyphenols decreased the
number of malignant tumors per rat by 80 percent compared to the
When the researchers analyzed blood and colon tissue samples,
they found a "considerable amount of tea polyphenols in those
samples in treated animals, and those levels of tea polyphenols
were comparable to the human situation after ingestion of tea
leaves or tea beverage," Xiao noted.
The researchers believe these findings will pave the way for
clinical trials with green tea polyphenols in humans
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