There’s a constant flow of new studies touting the benefits of tea for everything from lowering bad cholesterol levels and reducing the risk of heart disease to preventing cancer and cavities. Meanwhile, grocery-store tea aisles are starting to resemble medicine cabinets, with tea boxes boosting the presence of chemicals called antioxidants (Lipton says its black or green tea has 190 milligrams per serving), and a number of special “healthy” teas.
But although tea has been associated with improving health since it was discovered more than 4,000 years ago, studies so far are far from conclusive. Scientists are still trying to figure out how tea works in the body, and while research relating to certain medical conditions is further along than it is for others, a large-scale human clinical trial has yet to be done…
The modern quest to discover the effect of tea on health began about a decade ago. In the early 1990s, the tea industry “primed the pump” and funded research in various areas such as cancer, cardiovascular health, oral health and metabolism, says Joe Simrany, president of the Tea Council of the USA, a U.S. trade association that promotes January as “National Hot Tea Month.”
Now, Mr. Simrany says, hundreds of studies are done on tea each year, some funded by the National Institutes of Health and the American Cancer Society, among other organizations. Meanwhile, sales of tea in the U.S. grew to about $5 billion in 2002 from $1.84 billion in 1990. About 90% of tea consumed in the U.S. today is black and 10% green.
Real tea, and the type researchers are focusing on, comes from the Camellia sinensis, a white-flowered evergreen shrub. But the shade of the tea depends on the picking and processing of the leaves and buds and their contact with oxygen.
Black teas such as darjeeling and ceylon result when the leaves are fully fermented, while oolong comes from partially fermenting leaves. Green tea results from withering, and then heating, dried leaves at a very high temperature, while white tea arises when the plant’s silver-haired buds are plucked by hand in late March before blooming, air-dried and steamed. (Herbal teas, which don’t share the same health claims as those from Camellia sinensis, bear the name of the plants they come from.)
All colors of tea contain chemicals called flavonoids, which are also found in beverages such as grape juice and beer. Tea flavonoids, or polyhenols, have been shown in the lab to neutralize free radicals — the unstable atoms or molecules that can damage elements in the body and lead to diseases such as cancer. There is little evidence so far, however, that the tea polyphenols act the same way in the human body. [WSJ]
