What Is It
The traditional process that yields green tea is simple: The leaves from the tea plant are first steamed, then rolled and dried. The steaming kills enzymes that would otherwise ferment the leaves. With other types of tea, the leaves are allowed to ferment either partially (for oolong tea) or fully (for black tea). The lack of fermentation, however, gives green tea its unique flavor and, more important, preserves virtually all of the naturally present polyphenols (strong antioxidants that can protect against cell damage). Other substances in green tea that also may be beneficial are fluoride, catechins, and tannins.
What Does It Do
Green tea possesses compounds that may provide powerful protection against several cancers and, possibly, heart disease. Studies indicate that it also fights infection and promotes longevity.
• May help prevent cancer.
• Protects against heart disease.
• Inhibits tooth decay.
• Promotes longevity.
The rate of certain types of cancer is lower among people who drink green tea. In one large-scale study, researchers found that Chinese men and women who drank green tea as seldom as once a week for six months had lower rates of rectal, pancreatic, and possibly colon cancer that those who rarely or never drank it. In women, the risk of rectal and pancreatic cancer way nearly cut in half. Preliminary research suggest that green tea may also fight breast, stomach, and skin cancer.
Studies investigating how green tea might guard against cancer have pointed to the potency of its main antioxidant, a polyphenol dubbed EGCG (for epigallocatechin-gallate). Some scientists believe EGCG may be one of the most effective anticancer compounds ever discovered, protecting cells from damage and strengthening the body's own production of antioxidant enzymes. According to a study from Ohio's Case Western Reserve University, EGCG seems to signal cancer cells to stop reproducing by stimulating a natural process of programmed cell death called apoptosis. Remarkably, EGCG does not harm healthy cells. In addition, research at the Medical College of Ohio indicates that EGCG inhibits the production of urokinase, an enzyme that cancer cells need in order to grow. In animals, blocking urokinase shrinks tumors, and sometimes causes cancer to go into complete remission.
The antioxidant effect of green tea's polyphenols may also help protect the heart. In test-tube studies, these compounds appeared to suppress the damage to LDL cholesterol, thought to be an initial step in the buildup of plaque in the arteries. A Japanese study of 1,371 men linked daily green tea consumption to the prevention of heart disease. In addition, green tea contains fluoride, which may help protect against tooth decay, and provides an overall antibacterial effect.
How To Take It
Dosage: You can get the benefits of green tea either by taking green tea capsules or tablets, or by drinking several cups of the brew each day. Your aim should be to get 240 to 320 mg of polyphenols.
When using supplements, buy those standardized to contain at least 50% polyphenols. At this concentration, two 250 mg supplements would provide 250 mg of polyphenols. Studies show that four cups of freshly brewed green tea also supply a recommended amount of polyphenols.
Guidelines For Use: Take green tea supplements at meals with a full glass of water. Drink freshly brewed green tea on its own or with meals. To make tea, use 1 teaspoon of green tea leaves per cup of very hot water. Let brew steep for three to five minutes; then strain and drink it.
Possible Side Effects
Green tea is very safe, both as a supplement and as a beverage. People who are sensitive to caffeine, however, may not want to drink too much green tea, because each cup contains about 40 mg of caffeine. (Indeed, for this reason, pregnant women and those who are breast-feeding should limit their consumption to two cups a day.) Green tea supplements, however, have very little caffeine. The recommended dose of green tea supplements provides the same amount of polyphenols as four cups of green tea, but generally contains only 5 to 6 mg of caffeine.
According to researchers at the University of Kansas, green tea's main antioxidant (EGCG) is 100 times more powerful than vitamin C and 25 times more potent than vitamin E in protecting DNA from the kind of damage thought to increase cancer risk.
Facts and Tips
• Green tea leaves contain hefty amounts of vitamin K, but a cup of brewed tea or green tea supplements have virtually none. This means that people taking anticoagulant drugs for heart disease (who may have been told to avoid large servings of food rich in vitamin K because of the vitamin's influence on blood clotting) can enjoy green tea with no fear of side effects.
• Drinking boiling hot green tea can damage your throat and esophagus and may over time increase your cancer risk. Try the traditional Asian method; Heat cold water until just before it boils (or boil it and let it cool for a few minutes), then pour the hot-but-not-boiling water over the tea leaves. This method also helps accent the delicate flavor of green tea.
• Imported from China, gunpowder tea is simply green tea presented in tiny pellets resembling gunpowder. When placed in hot water, the leaves slowly unfold.