TUESDAY, Jan. 11, 2005 (HealthDayNews) -- Eating a lot of red meat and processed meats such as salami and pastrami over a long period of time can increase your risk of colon cancer, researchers report.
A 20-year study of more than 148,000 adults aged 50 to 74 found those with the highest consumption of those meats were 50 percent more likely to develop cancer in the lower colon than those with the lowest consumption. The report appears in the Jan. 12 issue of the Journal of the American Medical Association.
This is not a groundbreaking finding, said Dr. Michael J. Thun, head of epidemiological research at the American Cancer Society.
"There have been 20 such studies looking at the relationship between consumption of red or processed meat and colorectal cancer, and most have shown a greater risk in people with higher consumption," he said. "But this is the largest study that I'm aware of so far, and it adds substantially to the available evidence about the relationship."
The study defined high consumption of red meat as eating at least three ounces a day for men, or two ounces a day for women. High consumption of processed meat was defined as eating it five or six days a week for men, two or three days a week for women.
The risk for those people was 50 percent higher than for those who ate red or processed meat no more than three times a week. Long-term consumption of poultry and fish was associated with a lower risk of colon cancer.
Those are numbers that could be important to the followers of the Atkins diet, which encourages consumption of meats, Thun said.
"The Atkins diet became popular just recently, so no one knows the health effects long-term," he said. "But the accumulating evidence that a diet high in red meat or processed meat increases the risk of colon cancer indicates that it would certainly be undesirable to remain on the Atkins diet long-term."
But meat consumption is "not in the same scale" with other risk factors for cancer, Thun added. Smoking is the most obvious example, but he cited two other factors most people do not always associate with cancer -- obesity and physical inactivity.
"High meat consumption is associated with at most a 50 percent increased risk for cancer of the lower colon," Thun said. "Obesity doubles the risk for all colorectal cancer, as does lack of physical activity."
The society's recommendations for risk reduction include maintaining a healthy body weight and regular physical activity. Screening by such methods as an annual fecal occult blood test, colonoscopy every 10 years and flexible sigmoidoscopy every five years is recommended for those over 50.
While Thun said he does not regard himself as a model, when questioned about diet he said, "I haven't eaten red meat for quite a while."
A more cautious approach is taken by Dr. Steven H. Zeisel, who is the American Institute of Cancer Research professor of nutrition at the University of North Carolina, Chapel Hill.
The study findings point to the need for a controlled trial that would assign people to different diets and follow them for years, he said. Since such a trial is not in prospect, he recommends moderation.
"Moderating red meat intake makes sense in terms of reducing the risk of colon cancer," Zeisel said. "But I don't think that anybody says that eating red meat now and then would increase the risk of cancer. There's no need to become a vegan or make drastic changes in diet. I would be moderating my intake a little more than I would have moderated before."
More information
A guide to colorectal cancer and its prevention is offered by the Memorial Sloan-Kettering Cancer Center.
