The three non-herbal teas-black, green, and oolong-all come from the same plant, Camellia sinensis. Their differences lie in the processing: Heating the leaves immediately after they've been chopped minimizes certain chemical changes and produces green tea; a brief delay in heating yields oolong tea, and a longer delay yields black tea.

All three forms of Camellia sinensis are unusually rich in a potent class of antioxidants called polyphenols. Antioxidants are important because they neutralize harmful free radicals, the highly unstable molecules produced by the body's normal metabolism and by exposure to chemicals, heavy metals, radiation, and the like. Lacking a vital part of their molecular structure, free radicals oxidize other molecules by snatching the missing part from them. That process can damage the body's cells, proteins, and fats-and, in theory, can help cause a wide range of diseases and possibly even hasten aging. To minimize the damage, the body uses antioxidants-some produced internally, others gleaned from food and drink-to help neutralize the radicals.

In theory, antioxidants can protect against disease and may help to explain why tea drinkers tend to be healthier. In laboratory and animal studies, the antioxidants in tea have been shown to help check the formation of certain carcinogenic compounds, disrupt several tumor-promoting enzymes, kill or at least slow the growth of actual cancer cells while leaving normal cells unscathed, and prevent normal cells from turning cancerous, mainly by shielding their DNA from oxidative damage

Other laboratory studies suggest that tea may help protect the heart by relaxing blood vessels; by inhibiting blood clots, which can trigger a heart attack or stroke; by shielding the "bad" LDL cholesterol from the oxidative damage that makes it stick to the walls of coronary arteries; and possibly by helping to improve blood-cholesterol levels. Other compounds in tea include fluoride and phytoestrogens, which researchers speculate may favorably affect bone-mineral density.

SUMMING UP
While the evidence of the health benefits of traditional tea is mounting, it's not. Yet clear whether it's the tea itself or other factors that result in the lower disease risks of frequent tea drinkers. Nonetheless, since drinking tea is safe, convenient, and inexpensive, there's little downside and possible health benefits for those who enjoy the beverage.

There is not yet enough evidence to make recommendations about how much of which type of tea to drink. But don't think of tea as a substitute for eating a varied diet rich in fruits and vegetables. The evidence that produce helps prevent disease is far stronger than the evidence for tea.