Tea: Second Only to Water : Part 3

by Food and Drug Administration (FDA)

(Page 3 of 3)

Yang describes studies in which laboratory animals fed green tea had reduced formation or growth of skin tumors, esophageal tumors, gastrointestinal tract tumors, and tumors of the liver, lung and pancreas. Black tea also has shown activity against skin, lung, liver, and esophageal tumors.

Results of epidemiological studies are murkier. Some indicate a protective effect of tea against certain cancers, others show no relationship, and still others show a higher incidence of some cancers, particularly esophageal, in heavy tea drinkers.

Although higher rates of esophageal cancer are seen in some parts of China, Iran and Japan, where tea consumption is high, it's not clear why. According to FDA research chemist Joseph M. Betz, Ph.D., "It's been bounced back and forth as to whether the high incidence is due to tea polyphenols or to proliferation of esophageal cells in response to physical damage to those cells cause by habitual consumption of a very hot beverage, as has been proposed by Dr. Bruce Ames at the University of California at Berkeley."

Yang reports that several case-control studies showed no association between esophageal cancer and drinking tea at normal temperatures (35 to 47 degrees Celsius, or 95 to 117 degrees Fahrenheit), but that ingestion of very hot tea (55 to 67 degrees Celsius, or 131 to 153 degrees Fahrenheit) was associated with twofold to threefold increases in risk.

He concludes that tea may reduce cancer risk in certain populations, adding that, "Depending on the etiology [cause] of the disease, the protective effect may be observed in selected cancers in certain populations but not in other situations." He advocates more studies on the chemical properties and biologic activities of tea and tea components — particularly of black tea, which is the major kind of tea consumed in Western countries and whose properties, he says, are poorly understood.

Polyphenols in tea are being looked at for a potential to lower heart disease risk also. Biochemist Joe Vinson, Ph.D., at the University of Scranton in Pennsylvania, found that hamsters fed green and black teas had lowered blood cholesterol levels and reduced LDL cholesterol oxidation. He also found that tea has an anti-clotting effect in rats, which could help prevent or reduce the severity of a heart attack.

Vinson is cautious about translating the results of his studies to humans, though, in part because the hamsters were given tea in amounts equivalent to two quarts a day for humans. And although he is encouraged by epidemiological studies in Japan and China that show less heart disease in people who drink lots of tea, he stresses that "the tea story has yet to be written as far as heart disease goes."

A. Richey Sharrett, M.D., Dr.P.H., at the National Heart, Lung, and Blood Institute in Bethesda, Md., agrees. Sharrett considers tea polyphenols potentially important in heart disease but is wary of epidemiological studies.

"People don't just live on tea," he points out, "and if you compare cultures, they differ in so many respects. To me, you have to fall back on the biochemistry — you want to know if polyphenols are antioxidants, if they are absorbed, and can you get direct evidence that they're effective against coronary disease."

"The Food and Drug Administration has not done any reviews of possible beneficial effects of tea," says John Vanderveen, Ph.D., director of FDA's Office of Plant and Dairy Foods and Beverages. "If we were to do it, it would be under the context of a health claim," he says, "and no one has submitted a request for a health claim."

Whether or not tea will ultimately prove of value in combating cancer, heart disease, or children's tumbling remains to be seen. In the meantime, cuppa tea, anyone?

Debugging the Dispenser

After a restaurant patron in Cincinnati complained last summer that his iced tea smelled like sewage, the city's health department sampled iced tea from several area restaurants. The study revealed high levels of coliform bacteria (from fecal matter), prompting the state of Kentucky to launch a similar survey of its restaurants. That study, too, found contaminated tea in many restaurants. Although no illnesses were reported, both jurisdictions last fall issued advisories to retail food establishments on how to properly prepare brewed iced tea.

"There was a similar situation in Texas back in 1987," says Thomas L. Schwarz, director of the division of cooperative programs in FDA's Center for Food Safety and Applied Nutrition, "and the problem was the same — the tea dispensers were not being properly cleaned and sanitized."

After the tea leaves are brewed, the hot tea is transferred from the brewer to a reservoir-type unit with a spigot for dispensing the tea. This unit has at its base a short section of tubing that goes from the reservoir to the spigot.

"What was found in 1987 and again recently," Schwarz says, "is that the dispenser is not being cleaned properly. Over time, the tubing and the spigot build up a heavy bacteria-laden residue, accounting for the high bacterial counts in some of the tea samples."

The solution to the problem is simple, Schwarz says. It requires disassembling, cleaning and sanitizing the dispenser, hoses, spigot, and other components. "If they dismantle the dispenser and clean and sanitize it at least once a day, as is recommended by FDA for retail food establishments, they shouldn't have any problems," he says, adding that no extra precautions need to be taken for home-brewed iced tea.

About the Author

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