Benefits of Green Tea
Tea and Cancer Prevention drinking tea is an ancient tradition that dates back to 5,000 years 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 particularly interested in antioxidants called catechins-found in tea.
1. What are antioxidants?
The human body constantly produces unstable molecules called oxidants, commonly known as free radicals. To become stable, oxidants steal electrons from other molecules and, in the process, damage cell proteins and genetic material. The 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 process of further allow the leaves to ferment and oxidize, black tea is produced. Perhaps because it is less processed, green tea contains high levels of antioxidants of black tea.
Although tea is consumed in a variety of ways and varies in its chemical makeup, one study showed maceration or green or black tea for about five minutes released over 80 percent of its catechins. Instant iced tea, on the other hand, contains a negligible amount of catechins (1).
3. What are the results of the laboratory?
In the laboratory, studies have shown tea catechins act as powerful inhibitors of cancer growth in several ways: they scavenge oxidants first cell injuries occur, reduce the incidence and size of chemically induced tumors, and inhibit the growth of 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. Food, environmental, and population differences may explain these inconsistencies.
Two studies in China, where green tea is a mainstay of the diet, has led to promising results. A study of over 18,000 men found tea drinkers were about half as likely to develop cancer of the stomach and esophagus, as men who drank little tea, even after adjusting for smoking and other health factors and Food (3). A second study in Beijing Dental Hospital found consuming 3 grams of tea per 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. NCI is evaluating the tea?
National Cancer Institute (NCI), researchers are also investigating the therapeutic use of green tea. A study recently completed but unpublished NCI studied the antitumor effect of green tea among prostate cancer patients. The 42 patients drank 6 grams of green tea, or about 4 cups a day for four months. However, only one patient showed improved short-term and nearly 70 percent of the Panel unpleasant side effects such as nausea and diarrhea. The study concluded drinking green tea has limited antitumor benefit for patients with cancer of the prostate (5).
Other ongoing NCI studies are testing green tea as a preventive agent against skin cancer. For example, it is studying the protective effects of a pill form of green tea against sun-induced skin damage while another explores the topical application of green tea, down precancerous skin changes.
