Green Tea Targets Cancer

2005-07-18 20:13

Green Tea

Speaking at an international conference on diet and cancer, researchers funded by the American Institute for Cancer Research (AICR) presented evidence that a major component in green tea may short-circuit the cancer process in a striking new way that scientists had not foreseen.

AICR experts also released the results of surveys showing that only 15 percent of Americans say they drink green tea on a typical day, and less than one percent of Americans are currently drinking enough green tea to match the average per capita consumption in Asian countries.

The AICR experts highlighted the low levels of green tea consumption in the United States in relation to what they called "intriguing evidence" from studies conducted among Asian populations that suggest a protective effect for green tea. They also pointed to the rapidly increasing number of laboratory studies exploring green tea's effects on a cellular level.

New Evidence That Green Tea Short-Circuits the Cancer Process
"We have determined that a unique quirk of biochemistry allows green tea's protective effects to extend to many different kinds of cells," said Dr. Thomas A. Gasiewicz, a Professor of Environmental Medicine at the University of Rochester Medical Center. "In fact, the active green tea substance, called EGCG, seems to target one protein that is particularly common throughout our bodies, and it does so with a degree of precision that cancer drugs still aren't able to match."

The protein in question is called HSP90, which is present at higher levels in many cancer cells. Scientists believe that in some circumstances, HSP90 helps to trigger the cascade of events that eventually leads to cancer.

When EGCG binds to this protein, however, it helps prevent these events from happening. This is important, because HSP90 is found throughout our bodies, in many different cells and tissues.

"If further research confirms that EGCG's ability to bind to such a basic and pervasive protein enables it to extend its protective effect throughout our bodies, it explains a scientific mystery," said Gasiewicz. "Studies that track the diets of human subjects over several years, particularly studies conducted in Asia, where green tea consumption is common, have associated regular usage of green tea with lower risk for cancers that are vastly different from one another."

Scientists suspect that many different mechanisms must be involved to explain Asian data linking green tea to the prevention of such diverse cancers as those of the breast, prostate, bladder, colon, stomach, pancreas, breast and esophagus. But this new finding shows that EGCG may be effective against an important "common denominator" for many different cancers, at the very start of the process.

EGCG Does What Cancer Drugs Can't Do... Yet
The protein called HSP90 is essentially a "helper" or "chaperone" protein, in that it exists to help stabilize other proteins and keep them together. Because it has to bind to so many different proteins it is present, in varying amounts, in all of our cells. In fact, it is referred to as a "promiscuous protein" because it is so pervasive.

But scientists have recently discovered that cancer cells tend to have higher levels of HSP90 than healthy cells. This has led scientists to try to develop pharmaceutical means to block HSP90, to keep it from sending the specific biochemical signals that can trigger cancer. So far, they have been unable to perfect a drug that is both highly specific and easy to administer.

What the AICR researchers have discovered is that the active substance in green tea already does what drugs still can't do: "EGCG targets HSP90, binds directly to it, and keeps it from passing on signals that can start the cancer process," said Gasiewicz. "As a result, potentially harmful genes are less likely to get turned on, and the cascade of events leading to cancer is cut off before it begins."

The fact that EGCG binds directly to a protein that is found everywhere in the body suggests that it may be able to provide effective and simultaneous cancer protection in vastly different tissues and organs, Gasiewicz said.

Surveys Show Very Low Green Tea Consumption in US
Given the possibility of such broad protection from a major component in green tea, AICR conducted two telephone surveys to gauge consumption levels among Americans. Results show that although green tea is higher in beneficial phytochemicals and lower in caffeine than black tea, coffee or colas, Americans rarely drink it.

"According to our surveys, only 15 percent of Americans say they drink green tea on a typical day, making it the least popular non-alcoholic beverage in the U.S.," said Jeffrey R. Prince, AICR Vice President for Education. "And even those who said they drank it every day drank far smaller amounts than are seen in Asian populations."

Average per capita consumption in Japan and China hovers around 3 to 4 cups per day. According to the AICR survey, less than 1 percent of Americans are drinking the equivalent amount (roughly 2 to 3 U.S. teacups) of green tea.

Another AICR survey asked about green tea consumption in a slightly different way. Nearly seven in ten Americans (68 percent) said they drank green tea rarely or never. According to a recent scientific study of Japanese food intake, only 8 percent of Japanese people say they drink green tea rarely or never.

"Clearly, Americans are not taking advantage of the health benefits green tea may offer," said Prince. "We think that people concerned about lowering cancer risk should consider adding green tea as another potentially protective food to a diet rich in plant foods and low in fat and salt."

More information about the AICR surveys on green tea consumption is available on the AICR website, www.aicr.org

Dr. Gasiewicz's EGCG study was presented on July 14 th at the International Research Conference on Food Nutrition and Cancer in Washington, DC. It was one of six scientific papers linking green tea to the prevention of cancer presented at the conference. The results were published recently in the journal Biochemistry. The study was coauthored by Ph.D. student Christine Palermo and undergraduate Claire Westlake.

The conference is hosted annually by the American Institute for Cancer Research and World Cancer Research Fund International.

The American Institute for Cancer Research (AICR) is the cancer charity that fosters research on diet and cancer and educates the public about the results. It has contributed more than $72 million for innovative research conducted at universities, hospitals and research centers across the country. AICR also provides a wide range of educational programs to help millions of Americans learn to make dietary changes for lower cancer risk. Its award-winning New American Plate program is presented in brochures, seminars and on its website, www.aicr.org AICR is a member of the World Cancer Research Fund International. - WASHINGTON, DC

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