MONDAY, April 19, 2004 (HealthDayNews) -- Green and black tea can slow down the spread of prostate cancer, while a highly touted antioxidant found in red wine, grapes and peanuts does not perform well as a cancer preventive, two new studies have found.
For the tea study, Susanne Henning, an associate researcher at the Center for Human Nutrition at UCLA's David Geffen School of Medicine, assigned 20 men, all scheduled for prostate removal due to cancer, to drink either black tea, green tea or soda, five cups a day for five days before surgery.
The aim was to see if substances called polyphenols found in tea might slow prostate cancer cell growth. Other researchers have found these polyphenols induce death in cancer cells.
In Henning's study, a piece of each man's prostate was cut out during the surgery and given to a pathologist, who then turned it over to the researchers for evaluation. When they looked at the proliferation of prostate cancer cells in the sample of tissue removed, there was a decrease in how fast new cancer cells appeared for men who had consumed either black or green tea, The same was not found in those who drank the soda.
"This is the first human study to show that EGCG (epigallocatechin gallate, a polyphenol in the tea) shows up in the prostate after drinking tea," said Henning, who presented her study April 18 at the Experimental Biology 2004 meeting in Washington, D.C. "Black tea is a bit better. This strengthens the idea that green tea and black tea help prevent prostate cancer."
For several years, researchers have focused on tea and its potential to prevent cancer, partly because in parts of the world where tea is consumed, the incidence of some cancers is lower.
The other study, presented at the same meeting, looked at the cancer-fighting ability of resveratrol, a dietary polyphenol, and did not produce the same promising results.
For several years, resveratrol has been discussed as a natural way to protect against both cancer and heart disease. But it's not known if dietary resveratrol will actually reach the proposed sites of action, said study author Thomas Walle, a professor of pharmacology at the Medical University of South Carolina, Charleston.
Oral dietary supplements of resveratrol are not likely to have any effect on breast and prostate cancer, Walle concluded after his study. He gave resveratrol both by mouth and intravenously to six healthy volunteers. Then they looked for resveratrol in the blood samples drawn later.
Only trace amounts reach the bloodstream, Walle said. "We are not trying to disclaim anything, but rather to answer a very basic question that is being asked by the drug industry all the time. When they introduce a new drug, they ask, 'Will it get into the circulation?'"
"It has been claimed that resveratrol may prevent breast or prostate cancer, and that may not be the case," Walle said.
Even though the bloodstream had only trace amounts of resveratrol, Walle said he has found in other studies that resveratrol does accumulate in ephithelial cells along the digestive tract, "So it could prevent cancer in those cells."
Henning said her findings are too premature to recommend that men drink black or green tea in hopes of preventing prostate cancer.
Dr. Herman Kattlove, a spokesman for the American Cancer Society, agreed: "It's a long distance from this data to any possible clinical effect."
Instead of focusing on single supplements or substances, Kattlove suggested boosting fruit and vegetable intake.
"Eating more fresh fruits and vegetables is protective from cancer," he said, adding it is highly unlikely a single substance in the foods provides the effect.
More information
To learn more about cancer prevention, visit the
American Cancer Society. To find out about prostate cancer, visit the
National Library of Medicine.
