Bad news for beef eaters: Red meat (search) really does increase your risk of colon cancer (search).

It's not exactly news. Many studies suggest that people who eat the most meat get the most cancer. Now a huge, 20-year study from the American Cancer Society (search) confirms these findings.

The bottom line: Those who eat the most red meat — beef and/or pork and/or processed meat products — get colon cancer 30 to 40 percent more often than those who eat these foods only once in a while.

The news is particularly bad for those who favor lots of lunchmeats, hot dogs and sausages. Eating lots of these processed foods raises colon cancer risk by 50 percent, reports Marjorie L. McCullough, ScD, senior epidemiologist at the American Cancer Society in Atlanta. McCullough and colleagues report the findings in the Jan. 12 issue of The Journal of the American Medical Association.

"The bottom line is that the people who were eating the most red meat had higher colon cancer risk than those eating the least," McCullough tells WebMD. "Very few of these lower-risk people ate no red meat. It is not that we are saying people can never have red meat. But this shows it is important to limit the amount of red meat you eat."

The researchers collected detailed information on the diets of nearly 150,000 men and women aged 50 to 74 living in 21 U.S. states. They collected data in 1982 and 1992-1993, and followed them through the end of August 2001. In that time, 1,667 of the study participants developed colon cancer.

The study took into account known colon cancer risks such as smoking, being overweight, daily aspirin use, little physical activity, alcohol use, age, and low fiber intake.

How Much Red Meat Is Safe to Eat?

The findings are sobering, given the amount of red meat Americans love to eat.

"For Americans, estimates of per capita red-meat consumption come out to a little more than five ounces per day," McCullough says. "That is a little higher than the highest level of red-meat consumption in this study."

People who ate more fish, chicken, and turkey than red meat had a lower colon cancer risk than those who preferred beef and pork.

"Those consuming higher amounts of poultry and fish, especially for the long term, had about a 30 percent lower risk of developing colon cancer compared to those who did not eat much poultry and fish," McCullough says. "People who had red meat two to three times as often as white meat had about a 50 percent higher risk of developing colon cancer."

So how much red meat is too much? Burger lovers, fasten your seat belts. In the study, high red meat consumption was three ounces a day for men and two ounces for women. That's right. Barely enough daily hamburger to cover your palm raises cancer risk.

How much red meat is safe? McCullough says the study wasn't designed to pinpoint a healthy amount of red meat. But the study found the lowest colon cancer risk in men who ate less than 1.5 ounces of red meat per day and in women who ate less than 1 ounce of red meat per day.

That's going to mean a change in diet for most Americans. McCullough suggests starting slowly.

"A good way to think of this is to plan your meals to have more poultry and fish than red meat," she says. "If in a typical week you have 21 meals, try having a small portion of red meat at just one meal a day and work from there. If you're having red meat once a day, think of cutting back to once a week. It is best to think of red meat as a special treat."

Of course, red meat isn't the only colon cancer risk factor, notes Walter C. Willett, MD, DrPH, chairman of the nutrition department at the Harvard School of Public Health in Boston. Willett's editorial accompanies the American Cancer Society study.

"To keep cancer risk low we now know that staying lean and active is one of the most important things we can do, along with not smoking cigarettes," Willett says in a recorded statement.

"Overall the evidence is that replacing red meat with some combination of fish and poultry, and maybe some nuts and beans as protein sources, will have a moderately beneficial effect for reducing risk of colon cancer," the statement says. "It will certainly have some beneficial effects for reducing heart disease as well."

By Daniel J. DeNoon, reviewed by Michael W. Smith, MD

SOURCES: Chao, A. The Journal of the American Medical Association, Jan. 12, 2005; vol 293: pp 172-182. Willett, W.C. The Journal of the American Medical Association, Jan. 12, 2005; vol 293: pp 233-234. Marjorie L. McCullough, ScD, senior epidemiologist, American Cancer Society, Atlanta. Walter C. Willett, MD, DrPH, chairman, department of nutrition; professor of epidemiology and nutrition, Harvard School of Public Health, Boston.