Benefits of Green Tea

Tea and Cancer Prevention Tea drinking is an ancientin size in mice that were fed green and black tea (1,
tradition dating back 5,000 years in China and India.2).
Long regarded in those cultures as an aid to good4. What are the results of human studies?
health, researchers now are studying tea for possibleAlthough tea has long been identified as an
use in the prevention and treatment of a variety ofantioxidant in the laboratory, study results involving
cancers. Investigators are especially interested in thehumans have been contradictory. Some
antioxidants-called catechins-found in tea.epidemiological studies comparing tea drinkers to
1. What are antioxidants?non-tea drinkers support the claim that drinking tea
The human body constantly produces unstableprevents cancer; others do not. Dietary,
molecules called oxidants, also commonly referred toenvironmental, and population differences may
as free radicals. To become stable, oxidants stealaccount for these inconsistencies.
electrons from other molecules and, in the process,Two studies in China, where green tea is a mainstay
damage cell proteins and genetic material. Thisof the diet, resulted in promising findings. One study
damage may leave the cell vulnerable to cancer.involving over 18,000 men found tea drinkers were
Antioxidants are substances that allow the humanabout half as likely to develop stomach or esophageal
body to scavenge and seize oxidants. Like othercancer as men who drank little tea, even after
antioxidants, the catechins found in tea selectivelyadjusting for smoking and other health and diet
inhibit specific enzyme activities that lead to cancer.factors (3). A second study at the Beijing Dental
They may also target and repair DNA aberrationsHospital found consuming 3 grams of tea a day, or
caused by oxidants (1).about 2 cups, along with the application of a tea
2. What is the level of antioxidants found in tea?extract reduced the size and proliferation of
All varieties of tea come from the leaves of a singleleukoplakia, a precancerous oral plaque (1).
evergreen plant, Camellia sinensis. All tea leaves are5. Is NCI evaluating tea?
picked, rolled, dried, and heated. With the additionalNational Cancer Institute (NCI) researchers are also
process of allowing the leaves to ferment andinvestigating the therapeutic use of green tea. One
oxidize, black tea is produced. Possibly because it isrecently completed but unpublished NCI trial studied
less processed, green tea contains higher levels ofthe antitumor effect of green tea among prostate
antioxidants than black tea.cancer patients. The 42 patients drank 6 grams of
Although tea is consumed in a variety of ways andgreen tea, or about 4 cups, daily for four months.
varies in its chemical makeup, one study showedHowever, only one patient experienced a short-lived
steeping either green or black tea for about fiveimprovement, and nearly 70 percent of the group
minutes released over 80 percent of its catechins.experienced unpleasant side effects such as nausea
Instant iced tea, on the other hand, contains negligibleand diarrhea. The study concluded drinking green tea
amounts of catechins (1).has limited antitumor benefit for prostate cancer
3. What are the laboratory findings?patients (5).
In the laboratory, studies have shown tea catechinsOther ongoing NCI studies are testing green tea as a
act as powerful inhibitors of cancer growth in severalpreventive agent against skin cancer. For example,
ways: They scavenge oxidants before cell injuriesone is investigating the protective effects of a pill
occur, reduce the incidence and size of chemicallyform of green tea against sun-induced skin damage
induced tumors, and inhibit the growth of tumor cells.while another explores the topical application of green
In studies of liver, skin and stomach cancer,tea in shrinking precancerous skin changes.
chemically induced tumors were shown to decrease