Aug. 4, 2000 -- Green tea has long been standard in Asian cupboards, and it's now becoming commonplace in kitchens and coffeeshops around the U.S. Research is beginning to show there's a good reason for that -- green tea may aid in the prevention of heart disease and some cancers.
When oxygen is used in our bodies for energy, one of the byproducts is an unstable molecule called a free radical -- like exhaust from a car. The free radicals attack our cells, damage them, and increase the possibility of many kinds of disease.
Antioxidants, which can be found in many foods but especially in fruits and vegetables, act as sponges to soak up many of the free radicals and prevent or repair the damage to cells. Supplements containing vitamins C, E, and A or beta-carotene also may help in the cleanup.
"Not only vitamin supplements but also drinks that contain high levels of antioxidants could prevent these chronic disorders," says H. Sung, from the Asan Medical Center in Seoul, Korea. "Red wine is one of the best known of such drinks, and the green tea favored by Orientals also contains high levels of antioxidants."
Green tea was first shown to have an impact on cancer in laboratory animals nearly 20 years ago, with the first laboratory study suggesting a possible effect in human cancers following in 1988. Since then, drinking green tea has been associated with reduced risk of many cancers, including those of the esophagus, lung, and breast, as well as heart disease.
Although there still remains some controversy, it is beginning to appear that all types of tea are not created equal. Green teas are made from the dried leaves of the plant while oolong and/or black teas are first fermented. The fermenting process reduces the amount of antioxidants per cup and may lessen the protective effect.
There is no good guidance yet for those wondering about how many cups of green tea should be on the daily menu. The 1988 study showed that the greatest protective benefit for stomach cancers was gained by drinking at least 10 cups a day. In another case, those drinking between eight and 10 cups of green tea a day had milder cases of breast cancer at the time of diagnosis, a greater likelihood of a better prognosis, less risk of spreading, and longer survival.
Sung's study -- published in the European Journal of Clinical Nutrition-- looks at the antioxidant capacity of green tea and also indicates that the amount consumed is important. Specifically, they found that a single cup of tea didn't affect antioxidant activity at all, while increasing amounts had more impact -- and the more, the better.
Sung stresses, however, that "the roles of each component of green tea in the increase of antioxidant capacity still needs further investigation."
Lenore Arab, PhD, a professor of nutrition at the University of North Carolina at Chapel Hill, notes that there have been a lot of very encouraging research on the potential effects green tea may have in preventing and limiting cancers.
"I am becoming increasingly impressed with the amount of information that is coming out that supports an effect for green tea in particular," Arab says. "Our analysis shows that it might well have a protective effect on cancers. I have been encouraged to pursue this further."
In fact, she recently has switched from coffee to green tea as her beverage of choice. She does stress, however, that this has been based on her interpretation of studies that haven't clearly proven that there is any effect in humans.
And as a boost to those who like to brew, there is very little information to suggest there are any serious side effects of drinking green tea.
"The studies that have been done so far show benefits from consuming green tea," says Hasan Mukhtar, PhD, from Case Western Reserve University in Cleveland. "There is a reasonable amount of good data that show green tea consumption could have beneficial effects on the onset and progression of certain cancers and [heart] disease. None of these studies have provided any evidence that these amounts would be harmful."
The next question would be how best to brew the tea?
In Korea, the tea manufacturers recommend placing a bag with 2 to 5 grams of tea into hot water. Remove the bag, then repeat two to three times. Enjoy.