By Sally Squires
Tuesday, July 17, 2007
Michael Seidman, director of the Center for Integrative Medicine at the Henry Ford Health System in Detroit, hates the taste of green tea. But that doesn't stop him from drinking a cup five days a week. When he's done, Seidman squeezes the liquid out of the tea leaves and then -- get this -- eats them.
The leaves are so bitter that Seidman immediately brushes his teeth to remove the taste and to be sure that the tea doesn't stain his tooth enamel. "My wife just looks at me and rolls her eyes," says Seidman, an ear, nose and throat surgeon who also has a degree in nutrition. "But there's no doubt in my mind that green tea has many health benefits."
Other scientists are not so convinced. "There are hundreds, if not thousands of papers on tea, but the results are often split," notes tea researcher Jack F. Bukowski, an assistant clinical professor of medicine at Harvard Medical School.
So where one study finds that tea boosts immune function, another shows no effect. Most of the research has been limited to animals. Scientists have yet to examine all the properties of green, black, oolong and white tea. They don't yet know if the variety of tea -- Darjeeling vs. jasmine green tea, for example -- could make a difference. Or what effect there may be from drinking tea straight or mixing it with milk, sugar, lemon or other spices. There isn't even agreement on whether a cup of tea means the barely four ounces you sip from fine china or the hefty 16 ounces in an oversize mug.
"Tea has big possibilities," says Bukowski, who has spent 15 years studying the ancient beverage. "But we have a long way to go before we can confirm the health benefits."
None of that has stopped interest in tea from coming to a full boil. In January, Coca-Cola introduced Enviga, a green tea beverage said to "help you burn calories" by boosting metabolism. Last year, a Japanese company petitioned the Food and Drug Administration for permission to label green tea as offering protection against heart disease. (The agency denied the request, citing "supportive but not conclusive results.")
One substance in tea, the tongue-twisting epigallo-catechin gallate (EGCG), appears to reduce psoriasis, prostate cancer and colon tumors (at least in animals) and is now an ingredient in a growing number of foods, beverages and dietary supplements. But that's just one of the components of tea that may have health benefits.
Second only to water as the most widely consumed beverage in the world, tea is also one of the oldest. Introduced about 5,000 years ago in China, tea became a common drink in the Sui dynasty of the 6th century and reached Japan around 580, according to "The Romance of Tea," an authoritative history of the beverage published by William H. Ukers in 1936. In 1662, Catherine of Braganza -- the Portuguese-born wife of King Charles II -- became the first tea-drinking British queen. William Penn is credited with introducing tea to Pennsylvania.
Tea drinking plummeted in the Colonies after the Boston Tea Party. But by the early 20th century, Americans were drinking enough tea to invent the tea bag and introduce iced tea.
In 2006, more than 2.25 billion gallons of tea were sipped in the United States, according to the Tea Association, an industry group. That works out to about 132 cups per person per year. Even so, consumption here lags behind that in much of the world, particularly China, Japan and other parts of Asia, "where they drink tea all day long like we drink bottled water," Bukowski says.
U.S. tea drinkers are concentrated in the Northeast and the South, where sweet tea is the rule. As in most Western countries, black tea is preferred over green tea. Unlike people in the rest of the world, Americans consume 85 percent of tea iced rather than hot, according to the Tea Association.
Tea leaves are plucked from a warm-weather evergreen shrub, Camellia sinensis, that is indigenous to China and India but now also thrives in mountainous regions from Argentina to Malawi. Oolong tea is exposed to the air to oxidize for two to three hours after harvesting, while black tea is oxidized for up to four hours. (As for the wide range of herbal teas, they're made from the roots, leaves and flowers of other plants and are not technically tea at all.)
Neither green tea nor white tea, which is made from the tender, young leaves of the tea plant before they turn color, is allowed to oxidize after harvesting. Some scientists think that may give them a nutritional edge, since they may contain higher amounts of antioxidants. These substances help protect against cancer and appear to counteract the chronic inflammation that contributes to heart disease, arthritis and other chronic illness.
A growing number of studies suggest such potential benefits from tea as improved mental alertness, lower blood cholesterol and triglyceride levels, reduced blood pressure, lower risk of breast, colon, lung, ovarian and prostate cancer, as well as possible protection again Type 2 diabetes and maybe even help with weight loss. But even if such findings are confirmed, you'd need to drink a lot of tea to reap any benefit.
"The research suggests that drinking one to two cups of tea per day may not be enough," Bukowski says. "You may need more like five to 10 cups per day." Ounce for ounce, tea contains about half the caffeine found in coffee, so that could be a lot of caffeine. Whether decaf works as well is not yet clear.
For the biggest punch of antioxidants and other potentially healthful ingredients, drink tea shortly after brewing it. And resist the temptation to reuse tea bags, since that produces a less potent brew.