Ingredients in Green Tea Can Protect Against Cancer, Heart Disease
WebMD News Archive
Dec. 2, 1999 (Atlanta) -- Lately, green tea has been touted as an elixir for
a myriad of illnesses, including heart disease and cancer. However, a
researcher from Rutgers University says that while preliminary data point to
tea's curative powers in animals, nothing has been proven in humans. In fact,
writes Chung S. Yang, PhD, in an editorial column in the November/December
issue of the journal Nutrition, "if such beneficial effects do exist
in humans, they are likely to be mild."
Tea has been a popular beverage for centuries in countries like China,
Japan, India, and England. In fact, tea consumption in the world ranks second
only to water consumption. Recently, the United States has experienced a surge
in tea drinking. But tea's unique flavor is not the only reason consumers are
increasing their tea consumption. Recent research has shown that tea may
protect against several types of cancer, it may reduce the risk of heart
disease and stroke, and it has greater antioxidant power than many fruits and
vegetables. That is, if you drink a lot of it.
The three basic tea types come from the evergreen shrub Camellia
sinensis. Black, green, and oolong teas are produced from the tea plant by
varying the processing conditions. Black tea is produced by fermenting the
leaves, while green tea leaves are not fermented. Oolong teas go through a
shorter fermentation period than black teas and are regarded as semi-fermented.
All three kinds go through a heating process to halt fermentation.
Although most people drink black tea (made from fermented leaves), about a
quarter of all tea consumed is green (unfermented). All teas from Camellia
sinensis contain compounds known as polyphenols -- a class of bioflavonoids
-- which are found in all plants. Polyphenols have anti-cancer, antioxidant,
anti-bacterial, and anti-viral properties. Besides tea, these compounds are
especially high in coffee, red grapes, kidney beans, raisins, prunes, and red
It is believed that green tea guards against cancer by scavenging for free
radicals, which are the by-products from all the chemical reactions that occur
in the body -- like the exhaust from an automobile. Free radicals can damage
the cells that block the action of cancer-causing agents, or carcinogens, and
detoxify them. Tea polyphenols also may limit cell replication, the primary
characteristic of cancer.
In one widely publicized study, researchers at the Case Western Reserve
University School of Medicine, in Cleveland, reported that an ingredient in the
polyphenols in green tea kills cancer cells while sparing healthy cells. In the
study, reported in the Dec. 17, 1997, issue of the Journal of the National
Cancer Institute, the researchers tested this ingredient, EGCG, on
cancerous human and mouse cells of the skin, lymph system, and prostate and on
normal human skin cells. They found that EGCG caused cell death in cancer cells
while leaving healthy cells unharmed.