Green tea may help explain lower cancer rates in Asia
NEW YORK (Reuters) -- Smoking is a well-known cause of heart disease and lung cancer, but the rates of these diseases have remained inexplicably low in Asian countries where smoking is common. Researchers say there is growing evidence that green tea is one piece of the puzzle.
Writing in the Journal of the American College of Surgeons, Yale University researchers detail the body of evidence linking green tea to better heart health and a lower risk of cancer.
No one is suggesting that smokers ignore the danger of the habit and simply drink green tea. But research indicates that the tea's high concentration of antioxidants called catechins may offer a range of health benefits, according to Dr. Bauer E. Sumpio and his colleagues at the Yale University School of Medicine in New Haven, Connecticut.
Antioxidants help quench molecules known as oxygen free radicals that, in excess, can damage body cells and potentially lead to disease. Free radicals are natural byproducts of normal body processes, but they are also generated by external sources such as tobacco smoke.
In Japan, China and other Asian countries, it is a social custom to drink green tea, which is less processed -- and richer in catechins -- than the black tea commonly consumed in the West.
And it's possible that this habit helps explain the so-called "Asian paradox," according to Sumpio and his colleagues.
This paradox becomes clear when looking at global health statistics, the researchers note. For example, for every 100,000 U.S. men, 348 will die of coronary heart disease each year. The figure for Japanese men is 186, despite the nation's higher rate of smoking.
Coronary heart disease develops when the arteries feeding the heart become hardened and narrowed due to the buildup of cholesterol-containing plaques on the artery walls. According to Sumpio's team, lab research suggests that that green tea catechins -- particularly one called EGCG -- may help thwart the CHD process through their effects on "bad" LDL cholesterol.
The antioxidants may also help keep artery walls functioning smoothly, as well as inhibit blood cells from sticking together and forming clots.
Similarly, lab studies suggest that EGCG and other green tea antioxidants may block tumor formation or growth in a number of ways. This may, according to the researchers, help explain why the lung cancer death rate in Korea is unexpectedly low.
The rate of lung cancer death among Korean men is less than 40 per 100,000, versus 67 per 100,000 among U.S. men. The difference among women is more stark: 13 per 100,000 in Korea, compared with 45 per 100,000 in the U.S.
This is despite the fact that 37 percent of Korean adults smoke, while only 27 percent of Americans do.
The global disease patterns are not that simple, however; China has a higher CHD death rate than the U.S. and many other Western nations, and the rate of death from lung cancer is about the same among Japanese and American men. Green tea, according to Sumpio, is no substitute for kicking the smoking habit.
"Smoking cessation is the best way to prevent cardiovascular disease and cancer," he said in a statement.
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