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Green Tea's Counteracts Tobacco and Dixon's Effects
August 04, 2003
Green tea's ability to fight cancer is even more potent and varied than
scientists suspected, say researchers who have discovered that chemicals in
green tea shut down one of the key molecules that tobacco relies upon to cause
cancer. It's a find that could help explain why people who drink green tea are
less likely to develop cancer.
While green tea has been much-ballyhooed for its anti-cancer effects as well
as other purported abilities such as preventing rheumatoid arthritis and
lowering cholesterol, just how the substance works has been a mystery.
Scientists do know that green tea contains chemicals that are anti-oxidants and
quench harmful molecules. But its effects on the AH receptor have not been
thoroughly evaluated until now.
"It's likely that the compounds in green tea act through many different
pathways," says Gasiewicz, professor and chair of Environmental Medicine and
director of Rochester's Environmental Health Science Center. "Green tea may work
differently than we thought to exert its anti-cancer activity."
Gasiewicz and Palermo showed that the chemicals shut down the AH receptor in
cancerous mouse cells, and early results indicate the same is true in human
cells as well.
Graduate student Christine Palermo and adviser Thomas Gasiewicz, Ph.D., set
out to measure the effects of the chemicals found in green tea on a molecule
known as the aryl hydrocarbon (AH) receptor, a molecule that frequently plays a
role in turning on genes that are oftentimes harmful. Gasiewicz has previously
shown how both tobacco smoke and dioxin manipulate the molecule--a favorite
target of toxic substances --to cause havoc within the body, and currently he's
working with scientists at the James P. Wilmot Cancer Center to clarify exactly
how substances like tobacco smoke cause cancer.
The team isolated the chemicals that make up green tea and found two that
inhibit AH activity. The two substances, epigallocatechingallate (EGCG) and
epigallocatechin (EGC), are close molecular cousins to other flavonoids found in
broccoli, cabbage, grapes and red wine that are known to help prevent cancer.
In the laboratory the AH-inhibiting effects of green tea become evident when
EGCG and EGC reach levels typical of those found in a cup of green tea. But the
scientists say that how green tea is metabolized by the body is crucial to its
effectiveness, and that results in the laboratory don't necessarily translate
directly to the dinner table.
"Right now we don't know if drinking the amount of green tea that a person
normally drinks would make a difference, but the work is giving us insight into
how the proteins work," says Palermo, who enjoys cold green tea herself. "There
are a lot of differences between various kinds of green tea, so a lot more
research is needed."
The finding by scientists at the University of Rochester's Environmental
Health Science Center appears in the July 21 issue of Chemical Research in
Toxicology, published by the American Chemical Society.
University of Rochester Press Release,
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