TEA STEEPED IN HEALTH RESEARCH
-Shari Roan

March 10, 2003 - When it comes to a societal tonic, Americans have long preferred coffee over tea. But although coffee may be good, it's increasingly hard to ignore the evidence that tea is good for you.

Long viewed simply as a reason to relax in the middle of a stressful day or as a folk remedy for colds and digestive problems, mounting research suggests that drinking tea could lower the risk of developing several serious illnesses, including heart disease, cancer and osteoporosis. Almost 300 tea studies were completed last year alone.

Tea is as hot among consumers as it is among researchers. In the United States, sales rose from $1.84 billion in 1990 to an estimated $5.03 billion in 2002, according to the Tea Council of the USA, a trade organization. Though consumption per person still lags far behind that of many countries, the numbers reflect a soaring interest in this ancient brewed drink.

The recent findings have made a believer out of Andrea Emmerich, 38, who was shopping recently at Elixir Tonics & Teas, a Los Angeles store and tea garden. A few years ago, Emmerich said, she decided to change her lifestyle to become healthier. "And I got into this whole tea world."

No one is saying that tea is a cure-all or that you should drink it daily for good health, said Jeffrey Blumberg, a tea researcher at Tufts Nutrition Center in Boston. "The evidence is compelling that something is going on," he said. "But I wouldn't call it definitive."

The belief that tea improves health began with epidemiology, observations that certain tea-drinking cultures have a lower incidence of disease. For example, the Japanese, who drink tea with most meals, have much lower rates of heart disease than Americans, who are not big tea drinkers.

Such observations are obviously not proof - the English, who practically bathe in tea, show no special protection against heart disease - hence, the need for better research.

Recent research has focused on biomarkers, measurements of specific substances or chemicals in the body, that can reveal what is happening - such as whether tea consumption lowers cholesterol or kills harmful bacteria in the stomach. (Studies show tea does both.)

Still to come are large clinical trials in which people are assigned to drink a certain amount, and quality, of tea in a controlled setting over long periods of time. The tea drinkers' rates of disease will then be compared with the rates of those who don't drink tea.

But even without the research, scientists have a good idea of why tea appears to confer a broad range of health benefits. Tea - whether it's black or green or oolong - contains compounds called polyphenols, or flavonoids, powerful antioxidants that can eliminate free radicals that damage cells. Free radicals are produced naturally in the body as byproducts of chemical processes.

Because the antioxidants in tea are so powerful - one study estimated that tea antioxidants are 30 times more potent than the antioxidant vitamins C and E - they are believed to have an impact on many different areas of the body and on various disease processes.

Tea polyphenols are similar to the substances that make certain fruits and vegetables so healthful. Some researchers suggest that tea polyphenols confer a wide range of benefits because they are absorbed at different points throughout the digestive tract.

The amount of time tea is fermented during processing - which determines whether it becomes black, green or oolong - can alter the types of polyphenols found in tea, and some scientists are trying to identify which particular polyphenols may be the most powerful. Identification of specific polyphenols might even lead to drugs based on that substance. But other researchers believe that the entire range of polyphenols found in tea is what provides its preventive punch, Blumberg said.

Here's a look at some of the strongest recent evidence about tea and specific ailments:

Heart Disease
Polyphenols interfere with the free-radical molecules that cause low-density lipoprotein (or "bad") cholesterol to form plaque inside the heart's arteries. Some studies have shown that polyphenols have anti-clotting effects and can relax blood vessels, which makes them function better.

Such findings imply that tea could reduce the risk of heart disease or help tea drinkers fare better after a heart attack. In a study published last year in the journal Circulation, Dr. Ken Mukamal, an internist at Beth Israel Deaconess Medical Center in Boston followed more than 1,900 people who had suffered a heart attack. Almost four years later, heavy tea drinkers (14 or more cups a week) had a 44 percent reduced risk of dying compared with nondrinkers.Even patients who were moderate tea drinkers (less than 14 cups a week) showed some added protection compared with nondrinkers.

If the study findings can be duplicated and tea does indeed reduce heart attack deaths, "that is a major public health benefit," Mukamal said.

A Dutch study published last year also found that tea drinkers had half the risk of having a heart attack, and one-third the risk of a fatal heart attack, compared with nondrinkers.

Cancer
Various studies have suggested tea may reduce the risk of bladder, stomach, colorectal, esophageal and oral cancers.

Dr. Zuo Feng Zhang, a researcher at the Jonsson Cancer Center at the University of California, Los Angeles, published a study in 2001 showing that drinking green tea can reduce the risk of chronic gastritis by half. Chronic gastritis is an inflammatory disease that causes precancerous lesions, which can progress to stomach cancer.

"This is a very promising area," says Zhang. "The polyphenols can prevent cancer and also have vitamins C and E, which are very good for people's health. We have very strong confidence that the effect we found with chronic gastritis is real."

Zhang's work on stomach cancer is among several studies suggesting that tea has preventive properties. A 1994 study in the Journal of the National Cancer Institute found that drinking green tea reduced the risk of esophageal cancer by 60 percent, while a study presented at the Third International Symposium on Tea and Human Health last fall in Washington found that women who consumed high amounts of tea had a 60 percent reduced risk of rectal cancer.

Osteoporosis
Taiwanese researchers last year announced that longtime tea use appears to strengthen bones. The study, published in the Archives of Internal Medicine, found that hipbone density was 6.2 percent higher in people who drank tea habitually for 10 years or more, compared with nondrinkers. People who drank tea regularly for six to 10 years had a 2.3 percent higher bone density.

A British study, published in 2000 in the American Journal of Clinical Nutrition, also found higher bone density in women who drank at least one cup of tea a day.

Other Benefits
Early research suggests that tea can inhibit the growth of bacteria on teeth and that a white tea extract cream can protect against cellular changes in the skin caused by sun damage. But these studies have been small and preliminary, and much further work is needed.

The most common therapeutic use for tea in the United States - to ease cold symptoms - is also getting a closer look by scientists. A particular compound found in green tea, methylated epigallocatechin gallate, can block the production of two substances in the body that cause sneezing, watery eyes and coughing.

-March 10, 2003

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