Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: SUNDAY, March 20, 1994 TAG: 9403230118
SECTION: CURRENT PAGE: NRV-5 EDITION: NEW RIVER VALLEY
SOURCE: RANDY L. UDAVCAK STAFF WRITER
DATELINE: BLACKSBURG LENGTH: Long
The verdict: It doesn't - at least not directly.
The study, which appears in the current Journal of the National Cancer Institute, is the result of a 24-year odyssey by Tech's Center for Biotechnology into dietary sources of colon cancer. The odyssey culminated in a 1984 grant from the National Cancer Institute that allowed researchers to study reactions between the body's natural bacteria and certain compounds normally ingested in the diets of typical "westernized" countries.
Center director Tracy Wilkins coordinated the study, pooling the expertise of Roger Van Tassell, a senior research associate for the department of biochemistry and anaerobic microbiology; David Kingston, a professor of organic chemistry; and John H. Weisburger of the American Health Foundation in New York.
"We started off in 1972 on the elusive trail of any bad bacteria that might cause cancer in the colon or other places," Wilkins said. What they found was an ever-thickening plot that forced them to consider everything from how the body digests various foods, to differences in dietary patterns and cancer rates of people around the world.
"This work is impossible without having a combination [of people]," Wilkins said.
Wilkins traveled around the world collecting samples of bacteria normally found in the colon and human fecal material.
Kingston then identified and supplied the dietary compounds produced after cooking meat at high temperatures. Wilkins and Van Tassell combined those compounds with the samples Wilkins had collected and sent the aggregate material to Weisburger at the American Health Foundation for testing on rats and mice. "That's the way research is done," said Wilkins," by hooking up with people who do their job very well. [Kingston] does chemistry real well, we do microbiology real well, these guys [at the American Health Foundation] do carcinogenic testing. ... Running big research is a team effort."
Eventually, the study found that it is less likely that compounds from fried meats react with bacteria normally present in the colon to directly cause cancer, though indirectly the effects are still unknown.
"We were paid to study what the colonic bacteria do, and we did just about everything we could to study that," Van Tassell said. "We were trying to determine whether the bacteria in the colon transform these dietary carcinogens into compounds that directly cause colon cancer. What we found was that one major compound that transformed dietary carcinogens in fact appears not to be a carcinogen."
"I think people also have the snide view that everything causes cancer," said Wilkins. "It doesn't. I guess if we fed 'em [the rats] 10 tons of it, it could. But scientists are realistic in their testing, and it doesn't appear this compound is a threat."
He laughed. "It's nice to at least wipe one off the books and say it's no threat."
Nevertheless, the study is far from a conclusive statement on the causes of colon cancer, Wilkins said, noting that there are some 400 species of bacteria present in the human colon, and thousands of dietary compounds which they can come in contact with.
"Cancer is a very, very exasperating group of diseases on which to do research," he said.
Despite the limitations of the current study, the researchers say it adds to a body of colon cancer research that has grown markedly over the past decade. While many of the specific mechanisms by which colon cancer occurs remain a mystery, both Wilkins and Van Tassell say a number of general trends are showing up.
"If you look at anything that correlates pretty directly, it's the fat content of your diet," Wilkins said, noting that this pattern has been established by researchers worldwide. "You get a pretty direct link between colon cancer and dollars. As populations get enough money to buy foods that they want, they go for high fat foods."
For example, "the Japanese changed over in this generation to approach our rate of colon cancer; they used to have an extremely low incidence. Any vegetarian rural agrarian society usually has low colon cancer. If they don't have enough money for fat - it's almost a straight line relationship."
It also makes a big difference in how foods such as meats are prepared, Van Tassell said. "The risk of ingesting dietary carcinogens is reduced if you keep the temperature at which you cook your meat relatively low. What that means, is broiling and baking will generate fewer of these carcinogens than frying on a direct skillet in which there's oils and stuff that will facilitate the production of these carcinogens."
The higher the fat content of the meat, "the hotter that meat will get in the frying pan, because it conducts the heat more," Van Tassell said. "So therefore the higher the fat content, the more of these dietary carcinogens."
While more and more of these links are being established, however, Wilkins and Van Tassell add that there are still no easy answers.
"Reducing your fat intake enough to make a major impact on disease is very difficult with our foods that we like to eat in the United States," Wilkins said. "High fat [diet] is the one indelible like that's always there. We're trying to determine the exact mechanism, and if we can stop it somehow without giving up good steaks."
by CNB