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% of Americans say they drink green tea on a typical day, and less than 1% 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 U.S. 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.
"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 are not able to match."
The protein in question is called HSP90, which is present at higher levels in many cancer cells. Scientists believe, 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 the body, 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 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. However, 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.
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% 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 three to four cups per day. According to the AICR survey, less than 1% of Americans are drinking the equivalent amount (roughly two to three U.S. teacups) of green tea.
Another AICR survey asked about green tea consumption in a slightly different way. Nearly seven in 10 Americans (68%) said they drank green tea rarely or never. According to a recent scientific study of Japanese food intake, only 8% 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."