Wall Street Journal - January 26, 2004
Jennifer Saranow

"I started thinking about tea as a health thing," says the 25-year-old graduate student in New York. She currently has 18 boxes of tea in her kitchen cabinet -- mostly green -- and tries to drink at least three cups a day.

The problem is, Ms. Albert doesn't know why tea is healthy. "From what I have read, there is a lot of evidence that tea is good for you," she says. "But I'm not exactly sure about how it's good for you."

Ms. Albert is not alone in her confusion. 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.

"It's still an open question about how beneficial tea is really going to be -- how tea might work and whether it works in people," says Roderick Dashwood, a professor at the Linus Pauling Institute at Oregon State University.

The Food and Drug Administration isn't likely to allow retailers to make health claims on tea packages in the immediate future, but as research continues the possibility of health benefits may become clearer.

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.

Color Processing

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.

"There are many theories that have been proposed in literature for how tea works," says Chung Yang, chairman of the department of chemical biology at Rutgers University in Piscataway, N.J. "Many are based on studies in cell cultures, and whether that really occurs inside the body is still unknown."

So far, studies of tea and cardiovascular health have been mixed. Results from Europe and Asia tend to provide more consistent results showing a positive link between tea consumption and cardiac health than those from the U.S., perhaps because people in those regions drink more or stronger tea.

For example, a study of 4,807 Dutch men and women published in the American Journal of Clinical Nutrition in 2002 found that after six years, the risk of heart attack among those who drank more than three cups of black tea a day decreased 43% compared with those who didn't drink tea.

Another study, from researchers at Brigham and Women's Hospital and Harvard Medical School in Boston, published in the American Journal of Epidemiology in 1999, compared men and women who had suffered heart attacks with those who hadn't and found those who drank a cup or more of black tea daily had a 44% lower risk of an attack. But in a more recent study, from the same researchers, published in the American Journal of Clinical Nutrition in June, flavonoid intake from tea was not strongly associated with reduced risk of cardiovascular disease among the roughly 38,000 middle-aged women tracked for 6.9 years.

In general, scientists say tea's effect on cardiovascular health is the most promising area of research so far. In a recent review of nine studies published in the American Journal of Epidemiology in 2001, though researchers saw a stronger effect of tea in Europe than in the U.S., they concluded that the rate of heart attack decreased by 11% with consumption of three cups of tea a day.

The major problem with such population studies, however, experts say, is that it's hard to determine whether the beneficial effects are from tea, or because people who drink tea are also more likely to have healthy lifestyles. Offering up further evidence of tea's link to cardiovascular health are a number of clinical trials.

A Boston University School of Medicine study published in the journal Circulation in 2001 had 66 patients with coronary heart disease drink either 30 ounces of tea or water daily for four weeks. At the end of the month, blood-vessel functioning improved about 50% in the tea drinkers, while drinking water had no effect. Scientists hypothesize that tea flavonoids are encouraging cells on artery walls to open and thus preventing blood clots and hardening of arteries, which can lead to heart attack and stroke.

Joseph Vita, a researcher at Boston University Medical Center who conducted the study, says he's working on follow-up studies to determine the mechanism that leads to tea's beneficial effect on the artery-wall cells and whether the effect varies by the color and component of tea.

"For heart disease, we have very good evidence from human studies, but it's still not conclusive or final," says Balz Frei, director of the Linus Pauling Institute, who worked on the clinical study with Dr. Vita.

Cancer Prevention Unclear

Tea's link to cancer prevention has been more mixed. "I would say until about two years ago, I was extremely optimistic about tea and cancer prevention," says Linus Pauling's Dr. Dashwood, who focuses on tea and cancer. "I still remain fairly optimistic, but not as optimistic as I was. We need to do more studies and get more people involved."

In test-tube and animal studies, tea and its components have been found to inhibit the development of cancer of the esophagus, stomach, pancreas, skin, lung, mouth, liver, small intestine, breast, bladder, colon and throat. But such effects have not always been observed when tracking tea consumption and the incidence of the disease in humans.

So far, Rutgers's Dr. Yang says the most evidence exists that tea has an effect on esophagus, stomach and oral cancers. A study published in the journal Carcinogenesis in 2002 of more than 18,000 Chinese men found that tea drinkers were about half as likely to develop stomach or esophageal cancers as nondrinkers. Clinical trials have also shown that tea may help treat and prevent oral cancer. A trial involving 59 patients with precancerous oral lesions, published in 1999, found the size of the lesions decreased in 38% of the 29 patients treated with tea, suggesting tea might have a protective effect in oral cancer.

Another more recent study of 143 heavy smokers, published in the Journal of Nutrition in October, looked at the effect of tea consumption on DNA damage. Scientists at the Arizona College of Public Health, the University of Arizona and the Arizona Cancer Center in Tucson found that indicators of DNA damage dropped by 31% after four months among those who drank four cups of green tea daily, suggesting the possibility that regular green-tea drinking might offer some protection.

Little Evidence

Beyond cancer and cardiovascular health, tea has been linked to a host of health benefits, such as reducing the risk for osteoporosis, kidney stones and cavities as well as boosting metabolism and immune function. A study published in November in the Journal of Allergy and Clinical Immunology found that EGCG, an element of green tea, blocked the first step in an HIV infection, the binding of HIV to human T-cells.

But scientists say only a few studies have been done in these areas. "There is not very much data in that regard," says Jeffrey Blumberg, a professor at the Friedman School of Nutrition Science and Policy at Tufts University. "Those in my view are not ready for prime time and clearly need more study."

As for what consumers should do until more is known, recommendations from the experts vary. Some, like John Weisburger, a senior member of the Institute for Cancer Prevention, recommend drinking six to 10 cups of tea a day, since that tends to be the amount consumed in the population studies where positive results are observed.

Others, however, such as Howard Sesso, a researcher at the Harvard School of Public Health, say it would be premature to recommend specific amounts and say people simply should drink tea if they enjoy it. That's Ms. Albert's attitude. Even if tea turns out not to be healthy, she says she'll still drink it. "I enjoy drinking it," she says. "It's kind of a ritual at this point."

-- Ms. Saranow is a reporter for The Wall Street Journal Online in New York.

Write to Jennifer Saranow at jennifer.saranow@wsj.com

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