Scientists Seeking Possible Wonder Drugs in Tea
In this section...
Studies and Observations * Caffeine is not a Problem * They are Talking Real Tea * Tumors Reported Prevented
Excerpt from The New York Times.
By Jane E. Brody
If preliminary findings stand up to closer scientific scrutiny, tea - especially the green tea of the Far East - could become a popular and potent weapon in the war against chronic diseases.
Experts from around the world spent two days last week describing a laundry list of the potential benefits of tea, from preventing tooth decay to thwarting cancer. According to their reports, presented in New York at the first international symposium on the health effects of tea, it contains various substanves that may lower blood pressure and chlolesterol levels, stabilize blood sugar, kill decay-causing bacteria, block the action of many carcinogens and inhibits the growth of cncerous tumors.
Indeed, on scientist, Dr. Harold N. Graham, retired director of research for the Thomas Lipton Company, predicted, "Once we determine which components of tea are most useful pharmaceutically, it should be highly beneficial and still pleasing to people.". He said it might even be possible to enrich other foods with the biologicallu active substance with tea.
Studies and Observations
The symposium was jointly sponsored by American Health Foundation, an independent non-profit research organization that focuses on the realtionship between habits and health, and two groups that represent the tea industry, the Tea Council of the U.S.A. Inc. and the Tea Associated of the U.S.A. Inc.
Most of the suggested health benefits of tea have emerged from studies in laboratory animals and cell cultures, although some are supported by observed disease rates among tea-drinking people in various countries. for example, Japanese people who are heavy consumers of green tea have lower death rates from cancer of all types, especially cancer of the stomach, a major killer in Japan.
Coffee-drinking westerners are generally surprised to learned that, after water, tea is the world's most popular beverage. Nearly four-fifths of the tea procedured is so-called black tea in which the tea leaves are broken up and exposed to air to oxidize the chemicals known as polyphenols, which are the main biologically active ingredients of tea.
Caffeine is Not a Problem
About one-fifth of the tea drunk worldwide is green tea. The tea leaves are stabilized by moist or dry heat., which destroys the enzyme polyphenoloxidase and prevents oxidization of polyphenols. About 2 percent of tea consumed is oolong, in which polyphenols are only partially oxidized.
Although there has been some public concerns about the health effects of tea because of its caffeine content, researchers at the symposium said this popular drug was of minimal health consequences to most consumers. On average, brewed tea contains about half the caffeine found in coffee.
Dr. Arthur Basses, pharmacologist at the university of Miami School of Medicine, said the average American tea drinker ingests about 80 to 100 milligrams of caffeince a day and coffee drinkers twice that. At these levels he said, there was no evidence that caffeine related compounds caused or promoted the growth of cancer or damaged the heart.
Although caffeine can produce slight increased in blood pressure, most regular consumers rapidly become resistant to this effect, Dr. Basses said, adding that only a small percentage of patients with high blood pressure may be adversely effected by caffeine intake.
To date, most of the studies of the health effects of tea have involved extract of green tea, the predominant form consumed in Japan and a popular tea in China as well. The extracts are rich in polyphenols, the substance that Dr. Graham said make the "guts" of the tea, accounting for up to 40 percent of tea's dry solids. But teas can very widely in amounts of polyphenols and other compounds.
They Are Talking Real Tea
The chemical composition of a cup of tea depents not only on the type but also gentic variety, where and how it was grown, how it was processed and how it was brewed. The researchers emphasized that theur finding pertain only the real tea from the plant known scientifically as Camellia sinensis, not the so-called herbal teas, which can be made from scores of other plants and may contain few of none of the active compounds under study.
It is not yet known weather the oxidized polyphenols in black tea - the kind most Westerners consume - have the same actions in the body as the unoxidized polyphenols in green tea.
In several studies with laboratory animals, polyphenols have been shown to inhibit the activation of many common cancer-causing chemicals, thus preventing these agents from transforming normal cells into cancer cells.
Dr. Fung Lung Chung of the American Health Foundation reported that mice given green tea or one of the polyphenols derived from it in their drinking water developed considerably fewer lung tumors after being exposed to a cancer-causing nitrosamine from tabacco smoke.
Tumors Reported Prevented
In studies in rats exposed to a different nitrosamine, Dr. Junshi Chen of the Chinese Academy of Preventive Medicine in Beijing showed that two Chinese teas - Fujan oolong and jasmine - inhibited the development of esophageal tumors. Other experimenters working with laboratory animals reported beneficial effects of green tea extracts in warding off skin cancer, inhibiting proliferation of pre-cancerous cells and even in protecting arteries against the damage of high-fat diets.
The potential benefits of tea must now be tested in people under carefully controlled experimental conditions. It could be that people who choose to drink tea are inherently healthier or have different health-influencing habits than people who drink coffee or other beverages.
Testing these laboratory findings in human populations is difficult because it is hard to find a "clean" group for comparison: Most people either drink tea or coffee. Hence tea drinkers, in epidemiological studies, are often compared to interpreted with particular caution.
Most experts at the conference believe that it is premature to recommend tea for its purported anticancer effects. Dr. Allan H. Conney of Rutegers University College of Pharmacy said the relevance to humans of the laboratory findings needed further study as well as the side-effects of drinking large amounts of green tea. Some commercial products echoed the cautions, but others were less reluctant to push tea as a possible panacea. Dr. Yukihiko Hara, a food scientist for the mitsui Norin Company in Fujieda City in Japan said that 25 years of research with animals has convinced him that tea is a health-promoing and life-prolonging beverage.
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