For example, a diet rich in fiber was long considered a surefire way to help protect against the disease. But, a recent review of 13 studies in the Journal of the American Medical Association found fiber offered no overall protective effect when all risk factors were taken into account.
So, what should you do? Three words -- get a colonoscopy.
Colorectal cancer is the third most common cancer found in men and women in the United States, according to the American Cancer Society. An estimated 104,950 new cases of colon cancer and 40,340 new cases of rectal cancer were diagnosed in 2005 in the United States. Combined, they will cause about 56,290 deaths.
Colon and rectal cancer death rates are now nearly 50 percent higher in blacks than in whites, according to American Cancer Society research. As a result, the racial gap in colon cancer death rates are widening and experts partly blame blacks' low screening rates and less access to appropriate care. African-Americans need to be screened at the age at of 45.
For Dr. Blair Lewis, a professor of medicine at Mount Sinai School of Medicine in New York City, there's a way to avoid colon cancer that's already proven itself the gold standard -- regular colonoscopy screenings after age 50.
"Sometimes we can miss the forest for the trees," said Lewis, who's also a spokesman for the American Society for Gastrointestinal Endoscopy. "We talk about fiber, when we really should be talking about everyone being checked for colon polyps. There's no other malignancy that has a benign, removable precursor. It's that simple."
A colonoscopy utilizes a tiny camera inside a slender tube that's inserted through the rectum. The procedure lets doctors look for early signs of cancer inside the entire large intestine, from the rectum all the way through the colon to the lower end of the small intestine.
Even better, if a polyp is found, doctors can insert instruments through the same tube that will allow them to cut the lesion away, eliminating the cancer threat on the spot.
It's not the world's most pleasant procedure, however. Preparing for a colonoscopy requires powerful laxatives and sometimes several days of liquid diet. The patient also must be sedated for the procedure, so he or she can lose a day or more between the preparation and the colonoscopy itself.
Doctors estimate that about 64 percent of Americans who should be getting screened with colonoscopy are not.
"The numbers really are quite shocking," Lewis said. "The big reason that comes back is embarrassment. It's a horrible thing to die of embarrassment. It's just not appropriate. People should get checked."
Some people who want to avoid colon cancer but don't want to endure a colonoscopy often pursue a number of lifestyle strategies, said Dr. David Lieberman, chief of gastroenterology at the Oregon Health & Science University Hospital in Portland.
While these changes in diet and exercise are all good and will benefit the body overall, there's not a lot of evidence directly linking them to colon cancer prevention, he said.
Fiber seemed a winner early on. First reviews of data found a 16 percent lower incidence of colon cancer in the 20 percent of people with the highest fiber intake, according to the JAMA review.
But then researchers began compensating for other risk factors -- such as multivitamin use, red meat consumption, milk and alcohol intake -- and the perceived benefits of fiber disappeared.
"I think it shows how complicated it is to quantify fiber as a risk factor for colon cancer," Lieberman said. "Fiber comes in very different forms, and it often comes in forms that include other factors that could impact your risk.
"If taken with fruit, for example, also included in the fiber would be micronutrients and vitamins that could have an effect. It's very, very difficult therefore to study fiber in isolation," he added.
That's not to say Lieberman recommends against lifestyle changes to fight colon cancer.
He urges all his patients to reduce their alcohol intake if they are heavy drinkers, exercise at least several times a week, lower the amount of animal fat in their diet, and take a multivitamin to make sure they're getting the right amounts of calcium and vitamin D, folic acid and other important vitamins and micronutrients.
Lieberman also recommends a high-fiber diet, despite the recent study results.
"There's some compelling evidence that it probably plays some role in combination with other factors in fighting colorectal cancer," he said. "There are other benefits of fiber rather than just the colon. There's evidence it may be beneficial in managing cardiovascular disease, hypertension and constipation."
"I recommend pretty much what the Food and Drug Administration's guidelines recommend -- seven servings a day of fruits and vegetables, and whole grains. Can I prove that's necessarily going to reduce their risk of colon cancer? No. But I think it may reduce the risk overall," Lieberman said.