Tea, with about 40 milligrams of caffeine per brewed cup, has half the buzz of java. But unlike coffee, tea might have some definite health benefits. In animal research and in epidemiological studies, tea seems to protect against cancer and heart disease -- and it might also fight tooth decay.
Zhi Y. Wang, a research scientist at Columbia University's College of Physicians and Surgeons, is one of the world's leading tea investigators. He says lab studies on animals show that tea prevents the formation of cancerous tumors on a number of body sites.
Most of the work to date has been on green tea, which is steamed immediately after harvesting and is most popular in Asia.
In recent years, studies have also focused on black tea, created by allowing the tea leaves to ferment, giving it a darker color and distinctive taste. Oolong tea is fermented a bit. The results have been that black tea, too, appears to be protective in animal tests.
What gives tea its power are a class of phytochemicals -- plant compounds -- found in tea. These are so-called polyphenols, especially a group called catechins in green tea and theaflavins and thearubigins, produced from catechins in the fermentation process for black tea.
These apparently act as antioxidants, protecting cells from the ravages of the "free radicals," a potentially hazardous form of oxygen.
Dr. Wang and others note that tea research has gone from a simmer to a full boil in recent years. A not-yet-published review of studies by Dr. Wang and three colleagues notes that about 100 studies have been published since 1993, when Dr. Wang and others last reviewed the literature on tea and cancer prevention.
Yet he is circumspect about making any sweeping statements about tea and health.
"Tea may have benefits for humans," he says, but he adds that more human studies must be conducted. (One human study completed in China suggested that tea might help prevent heart disease.)
Epidemiological studies, which look at populations that regularly drink tea and try to look for possible health benefits, have been less conclusive than animal studies, says Hasan Mukhtar, a tea researcher at Case Western Reserve University in Cleveland.
Two older epidemiological studies, for example, seemed to show that tea drinking may have caused cancer of the esophagus. It now appears that the populations studied drank scalding hot tea and that the cancer is linked to the temperature of the drink, not the tea itself.
John H. Weisburger, senior member of the American Health Foundation, a private biomedical research center in Valhalla, N.Y., says tea also contains fluoride, which may protect against dental disease.
Dr. Weisburger's research is mainly supported by the National Institutes of Health and, in part, by tea producers.
"I can tell you the data so far show that those who drink about four or more cups of tea a day, they will have a health-promoting effect regarding heart disease and cancers of various types -- I'm not saying all types of cancer," says Dr. Weisburger.
He warns, however, that although green, black and even decaffeinated teas seem to offer benefits, consumers should check the labels on ready-to-drink teas to find out just how much tea they contain.
Dr. Wang doesn't go as far as Dr. Weisburger in promoting tea-drinking, but he notes that tea has been consumed in his native China for millenniums. He says tea was a medicinal herb before it was a beverage, and its curative powers are taken for granted in Asia. In China, it is regarded as an anti-inflammatory agent, an aid to wound-healing and, especially, a detoxifying substance.