Few people drink as much tea as physician John Weisburger, PhD. To him, each cup is more than just a steamy, comforting brew. What has led him to sip almost a dozen cups a day is the growing -- even astonishing -- evidence of tea's health-promoting properties.
According to Weisburger, tea is probably the single best thing you can add to your diet to ward off serious illness. This conviction will doubtless raise a few hackles among colleagues who give that honor to fresh fruit and vegetables. But Weisburger, who chaired two international scientific symposiums on tea and human health, is convinced of his message.
As evidence, he points to numerous studies suggesting that tea -- which made its way slowly to the west after originating in China more than 4,000 years ago -- can help prevent cancer and heart disease.
That would seem endorsement enough for tea, which, next to water, is already the most widely consumed beverage in the world. But the latest news about tea may invite even some loyal coffee drinkers to reconsider their choice: Researchers have found that tea -- with or without milk -- may actually help strengthen bones in postmenopausal women.
When Tea Prevails
Women age 65 to 75 who drank at least one cup of tea every day had significantly higher bone density in the spine and thighs -- common areas of fractures caused by osteoporosis -- than women of the same age who didn't drink any tea, according to a British study published in the April 2000 issue of the American Journal of Clinical Nutrition.
Comparing 1,134 tea drinkers to 122 non-tea drinkers, researchers at the University of Cambridge School of Medicine concluded that drinking caffeinated tea may protect against osteoporosis -- even though high caffeine intake has been linked with an increased risk of reduced bone density. As the British researchers point out, most studies are from populations where coffee serves as the major source of caffeine.
While researchers have yet to determine how tea works on bones, they suspect that antioxidants are key players. Tea antioxidants, called polyphenols, may be 100 times as effective as vitamin C and 25 times as effective as vitamin E, according to Weisburger. These antioxidants neutralize free radicals -- destructive by-products of the body's natural chemical processes. (Unfortunately for herbal tea drinkers, herbal teas are made from altogether different plants and spices and often contain no polyphenols at all.) Polyphenols' ability to protect the body from free radical damage may be behind tea's two best-studied benefits -- protection against cancer and lower heart disease risk.
A Barrier to Cancer?
Whether tea really helps prevent cancer is still under debate, but research in its favor is piling up. In one of the largest studies to date, Iowa researchers found that tea may be a powerful cancer fighter, according to a study published in the July 1996 issue of the American Journal of Epidemiology. The study of more than 35,000 postmenopausal women showed that those who drank at least two cups of black tea a day were 40% less likely to develop urinary tract cancer and 68% less likely to develop cancer in the digestive tract than women who did not drink tea.
Other research shows that tea may be a promising weapon in the fight against cancers of the stomach, bladder, esophagus, and prostate. Moreover, a study in China concluded that smokers who drink tea have a lower incidence of lung cancer, Weisburger noted in an April 1999 summary of the Second International Symposium on Tea and Human Health.
If tea indeed reduces cancer risk, it may be because its polyphenols pack a three-part punch. First, they prevent free radicals from damaging DNA, nipping cancer initiation in the bud. Second, they seem to prevent uncontrolled cell growth, slowing cancer development. And third, certain polyphenols may even destroy cancer cells without harming the surrounding healthy cells. When Japanese researchers combined cancer medications with polyphenols, the treatment was 20 times more effective than the cancer drugs alone, according to a study published in the March 1998 issue of the Japanese Journal of Cancer Research.
Playing on the Heart
Other scientists have found that the powerful antioxidants in tea also may help reduce the risk of heart disease. In one study, researchers found that women age 55 or older, who drank as little as a cup or two of black tea a day, were 54% less likely to have severe atherosclerosis, which can lead to heart attack or stroke, than those who did not. The more tea they drank, the less their risk, according to a study published in the Oct. 11, 1999, issue of the Archives of Internal Medicine.
That could be because the antioxidants work by preventing "bad" (LDL, low-density lipoprotein) cholesterol from promoting the plaque buildup that clogs arteries, researchers speculate. And by preventing atherosclerosis, tea antioxidants can help the arteries supply nourishing blood to the heart and the rest of the body.
A Matter of Health
All this research has probably got you putting a kettle on the stove. But until further studies are done, most health care professionals say the best way to prevent cancer, heart disease, and other diet-related ills is to enjoy a diet that's low in fat and high in fiber, with lots of antioxidant-rich foods.
But by all means, include some green or black tea. If Weisburger and other researchers are right, you could be one sip closer to a long and healthy life.
Originally published June 12, 2000
Reviewed and updated Jan. 9, 2002