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
cancer.
"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.
Visitors attend a folk
tea-making promotion activity in Hangzhou, East China's Zhejiang
Province in this April 14, 2006. Zhejiang is one of the major tea
producers in China, which has a tea history of about 5,000 years.
(newsphoto)
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
control group."
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.
(Agencies via China Daily December 10, 2007)
