Tea and Cancer Prevention
Tea drinking is an ancient tradition dating back 5,000 years in China and India. Long regarded in those cultures as an aid to
good health, researchers now are studying tea for possible use in the prevention and treatment of a variety of cancers.
Investigators are especially interested in the antioxidants-called catechins-found in tea.
1. What are antioxidants?
The human body constantly produces unstable molecules called oxidants, also commonly referred to as free radicals. To become
stable, oxidants steal electrons from other molecules and, in the process, damage cell proteins and genetic material. This damage
may leave the cell vulnerable to cancer. Antioxidants are substances that allow the human body to scavenge and seize oxidants.
Like other antioxidants, the catechins found in tea selectively inhibit specific enzyme activities that lead to cancer. They may
also target and repair DNA aberrations caused by oxidants (1).
2. What is the level of antioxidants found in tea?
All varieties of tea come from the leaves of a single evergreen plant, Camellia sinensis. All tea leaves are picked, rolled,
dried, and heated. With the additional process of allowing the leaves to ferment and oxidize, black tea is produced. Possibly
because it is less processed, green tea contains higher levels of antioxidants than black tea.
Although tea is consumed in a variety of ways and varies in its chemical makeup, one study showed steeping either green or black
tea for about five minutes released over 80 percent of its catechins. Instant iced tea, on the other hand, contains negligible
amounts of catechins (1).
3. What are the laboratory findings?
In the laboratory, studies have shown tea catechins act as powerful inhibitors of cancer growth in several ways: They scavenge
oxidants before cell injuries occur, reduce the incidence and size of chemically induced tumors, and inhibit the growth of tumor
cells. In studies of liver, skin and stomach cancer, chemically induced tumors were shown to decrease in size in mice that were
fed green and black tea (1, 2).
4. What are the results of human studies?
Although tea has long been identified as an antioxidant in the laboratory, study results involving humans have been
contradictory. Some epidemiological studies comparing tea drinkers to non-tea drinkers support the claim that drinking tea
prevents cancer; others do not. Dietary, environmental, and population differences may account for these inconsistencies.
Two studies in China, where green tea is a mainstay of the diet, resulted in promising findings. One study involving over 18,000
men found tea drinkers were about half as likely to develop stomach or esophageal cancer as men who drank little tea, even after
adjusting for smoking and other health and diet factors (3). A second study at the Beijing Dental Hospital found consuming 3
grams of tea a day, or about 2 cups, along with the application of a tea extract reduced the size and proliferation of
leukoplakia, a precancerous oral plaque (1).
5. Is NCI evaluating tea?
National Cancer Institute (NCI) researchers are also investigating the therapeutic use of green tea. One recently completed but
unpublished NCI trial studied the antitumor effect of green tea among prostate cancer patients. The 42 patients drank 6 grams of
green tea, or about 4 cups, daily for four months. However, only one patient experienced a short-lived improvement, and nearly 70
percent of the group experienced unpleasant side effects such as nausea and diarrhea. The study concluded drinking green tea has
limited antitumor benefit for prostate cancer patients (5).
Other ongoing NCI studies are testing green tea as a preventive agent against skin cancer. For example, one is investigating the
protective effects of a pill form of green tea against sun-induced skin damage while another explores the topical application of
green tea in shrinking precancerous skin changes.
Visit pcshealth.com for more articles and research on green tea.
About the Author
Robert is a writer in the Washington DC area and specializes in health and fitness. Visit pcshealth.com for more articles and research on green tea.
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