Study Finds Rare Tea May Be Healthiest of All

SAN FRANCISCO, March 29 — Known mostly to tea connoisseurs, white tea may have the strongest potential of all teas for fighting cancer, according to Oregon State University researchers. They will present their research today — the first on white tea — at the 219th national meeting of the American Chemical Society, the world’s largest scientific society.

Among the rarest and most expensive varieties of tea, white tea is produced almost exclusively in China. It belongs to the same species (Camellia sinensis) as other tea plants, but has a higher proportion of buds to leaves.
The buds are covered by silvery hairs, giving the plant a whitish appearance.

Some teas are processed more than others. White tea is rapidly steamed and dried, leaving the leaves virtually “fresh.” Green tea, composed of mainly leaves, is steamed or fired prior to being rolled. Oolong and black teas get their dark color and flavor from additional processing.

The researchers theorize that processing may play a part in tea’s cancer-fighting potential. The key is a class of chemicals called polyphenols.

“Many of the more potent tea polyphenols (‘catechins’) become oxidized or destroyed as green tea is further processed into oolong and black teas,” says Roderick H. Dashwood, Ph.D., a biochemist in the university’s Linus Pauling Institute and principal investigator of the study. “Our theory was that white tea might have equivalent or higher levels of these polyphenols than green tea, and thus be more beneficial.”

Chemical analysis confirmed their theory. White tea contains the same types of polyphenols as green tea, but in different proportions. Those present in greater amounts may be responsible for white tea’s enhanced cancer-fighting potential, says Dashwood.

Encouraged by reports of cancer-fighting chemicals in green tea, the researchers decided to test white tea to determine whether it has similar qualities. They brewed four varieties of white tea and subjected each to a laboratory test using bacteria. The test, called the Salmonella assay, determines whether a chemical can cause or prevent DNA mutations, the earliest steps leading to cancer.

White tea inhibited mutations more efficiently than green tea. This means it may have more potential to prevent cancer than green tea, says Gilberto Santana-Rios, Ph.D., a post-doctoral research associate with the institute, located in Corvallis, Ore.

The researchers, now performing experiments in rats, report that their latest data indicate that white tea may protect against colon cancer in particular. They attribute this to elevated levels of particular liver enzymes.

The researchers say more studies are needed to determine whether white tea actually protects people against cancer.

“White tea, and tea in general, is a healthy alternative to other popular drinks, such as sodas,” says Dashwood. “But to be on the safe side, one should maintain a healthy lifestyle that includes a diet rich in fruits and vegetables, regular exercise, and avoidance of smoking.”

Dr. Dashwood is Associate Professor in the Department of Environmental and Molecular Toxicology at Oregon State University. He also is Principal Investigator with the university’s Linus Pauling Institute.

Dr. Santana-Rios is a post-doctoral Research Associate with the Linus Pauling Institute.

Article source: http://www.sciencedaily.com/releases/2000/04/000410084553.htm