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Green Tea's Cancer Fighting Properties May Be Greater than First Realized
Adapted from a press release from the University of Rochester Medical Center.Green tea's ability to fight cancer is even more powerful and wide ranging than scientists have previously 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. The finding by scientists at the University of Rochester's Environmental Health Science Center appears in the July 21, 2003 issue of Chemical Research in Toxicology, published by the American Chemical Society.
Researchers at the University of Rochester Medical Center set out to measure the effects of compounds found in green tea on a molecule known as the aryl hydrocarbon (AH) receptor, a molecule found in the membrane of human cells that frequently plays a role in turning on genes that can cause harm. Research by a team headed by Dr. Thomas Gasiewicz, professor and chair of Environmental Medicine and director of Rochester's Environmental Health Science Center, has previously shown how both tobacco smoke and dioxin manipulate the molecule a favorite target of toxic substances known to cause severe disease-related problems in human beings.
Gasiewicz's team isolated various compounds found in green tea and found two that inhibit AH activity: epigallocatechingallate (EGCG) and epigallocatechin (EGC), both are close molecular cousins to other flavonoids found in broccoli, cabbage, grapes and red wine that are known to help prevent cancer.
While green tea has been much-touted 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. "Green tea may work differently than we thought to exert its anti-cancer activity." Gasiewicz and his team 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.
Laboratory experiments have shown that 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. However, Gasiewicz's study is one of the first to offer significant evidence that the anitoxidant properties of Green Tea may help fight cancer in the body. Scientists agree that how green tea is metabolized by the body is crucial to its effectiveness, and that results in the laboratory do not 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 Gasiewicz associate 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."
For this work Palermo received the award for best poster in the chemical carcinogenesis specialty section at the meeting of the Society of Toxicology in March 2003. Currently Polermo is studying exactly how green tea inhibits the AH receptor.
Gasieticz and Polermo's work is funded by the National Institute of Environmental Health Sciences and the American Institute for Cancer Research.