When you brew yourself a nice cup of tea, you're actually brewing a potent antioxidant mix. Tea has two substances in the catechin family—epigallocatechin gallate and epicatechin gallate—that are the most potent antioxidants of all the flavonoids. That makes tea into more than just a relaxing hot drink—it protects against heart disease, stroke, and cancer. Catechins help make your platelets, the tiny cells in your blood that make it clot, less “sticky.” When your platelets are less sticky, they're less likely to clot, which means you're less likely to have a heart attack or stroke from a clot in an artery. In one recent study, Dutch men who drank four cups of tea a day had a much lower risk of stroke than those who didn't—whether or not they also took vitamins. The catechins in tea also act as powerful antioxidants that can keep cancer from getting started.
Tea also has antibacterial action. It kills the bacteria that cause cavities and gum disease. Japanese men who drink a lot of green tea (nine or more cups a day) have lower cholesterol levels. The benefits of tea are found mostly in green tea, the kind used in China and Japan, because green tea has the most catechins. Green tea is made by steaming and then drying the fresh tea leaves. The steaming removes an enzyme that oxidizes the catechins and makes them less potent. Oolong tea (the kind served in Chinese restaurants) and black tea (the kind used in typical tea bags) aren't steamed. Instead, they're exposed to the air for a few hours and then allowed to ferment. The process oxidizes the catechins and makes them less potent. Even so, these teas are nearly as potent as green tea. One cup of green tea has about 375 mg of catechins; a cup of black tea has 210 mg.
You need to drink at least five cups of mild-tasting green tea a day to get any real benefit. If you don't want to drink that much, try supplements containing green tea extract. One capsule is roughly the same as five cups of tea.