CORVALLIS, Ore. - A new study has found that consumption of moderate amounts of green or white tea might provide a protection against colon tumors about as well as a prescription drug, sulindac, that has been shown to be effective for that purpose.
The research was just published in the journal Carcinogenesis by scientists from the Linus Pauling Institute at Oregon State University, in studies funded by the National Cancer Institute.
It may suggest some optional approaches to cancer prevention or therapy, especially for people who have trouble with the side effects that can be associated with regular use of non-steroidal anti-inflammatory drugs, or NSAIDs, such as sulindac or aspirin.
The study also indicated that routine consumption of green or white teas could be especially effective in combination with NSAIDs, and provide more cancer protection than either of the products separately.
"Tea is one of the most widely consumed beverages in the world, and recent upswings in the sales of green tea in the United States can be attributed to reports of potential health benefits against cancer and other chronic diseases," said Gayle Orner, an OSU research associate, in the report. "Teas exert significant protective effects in experimental animal models of skin, lung, esophageal, gastric, hepatic, small intestinal, pancreatic, colon, bladder and mammary cancer."
OSU's Linus Pauling Institute has been at the forefronts of efforts to examine the effectiveness of white versus green tea in blocking mutagens and preventing cancer. In the latest study, they examined green and white teas that have high levels of the protective polyphenols called catechins, and also compared these teas to sulindac. This drug is commonly used around the world for many purposes, including the prevention of certain colon cancers.
"We have evidence that consumption of tea at the same time as a person ingests mutagens can potentially block some of the effects of the mutagens through changes in metabolism," said Rod Dashwood, a professor in the Linus Pauling Institute. "But since everyone probably has some DNA damage in their cells, another question becomes, is there anything we can do to prevent cancer progression even after cells are damaged?"
To study this, the researchers used as a model a special group of laboratory mice that are genetically predisposed to tumor development, especially in their intestines.
A group of these mice that received no treatment each developed about 30 polyps in their colons. Other research has shown that a therapy with sulindac, the prescription NSAID, could cut polyp formation in these mice about in half.
But consumption of green tea, the scientists found, reduced the number of tumors in the mice from an average of 30 to 17; and consumption of white tea from an average of 30 to 13. Mice given both sulindac and white tea, in combination, saw a tumor reduction of about 80 percent, from 30 tumors to six.
"These are pretty exciting results," Orner said. "What's especially significant is that as far as we can tell consumption of tea has none of the side-effects of NSAIDs, which can be severe, including bleeding, ulcers and even death."
Use of NSAIDs for cancer prevention, heart disease and other concerns is increasingly common with many people, and high aspirin intake has been associated with a 40-50 percent decrease in colon cancer mortality, the researchers note in their report.
Although the complications from prolonged use of NSAIDs can be significant, they often are dose-dependent, the researchers noted in their report. Any cancer preventive agent that worked effectively in combination with NSAIDs and allowed use of lower dosages could be quite significant, the scientists said, and green or white tea consumption may fit that description exactly. Tea and its constituents also have been found to have many additional cancer-preventive mechanisms in their own right, the report said. These include antioxidant properties, induction of cell-cycle arrest, inhibition of oncogene expression, apoptosis induction, and other factors. In-vitro studies, they said, have suggested that tea plus sulindac may work in synergy to kill human lung cancer cells.
Consumption of black tea does not appear to the have the same anti-cancer properties in some situations as green or white tea, the researchers said. White tea, the least processed of all teas, has the highest levels of polyphenols and antioxidants, and is available at specialty tea stores, over the Internet, and in some grocery stories.
Polyphenols can also be purchased as a dietary supplement, the scientists said, but even less is known about how they function in the body, compared to the consumption of food products.
The level of tea consumption in humans that might provide useful levels of polyphenols could be equated to drinking about three coffee-sized mugs a day, the scientists said. This is based on studies in Japan with green tea and gastric cancer, where researchers essentially concluded, "the more the better."
Colon cancer is one of the leading causes of cancer death worldwide, and continued advances in its prevention and therapy will require better understanding of these diet and drug interactions, Dashwood said. Ultimately, a diverse regimen of drugs, dietary factors, routine checkups, medical and surgical treatments may all play key roles in preventing death from this cancer, he said.
Rod Dashwood, 541-737-5086
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