The cells in your large intestine are exposed to many types of substances that result from digestion and the activity of micro-organisms. What's more, the cells have a high turnover rate – your intestinal lining completely replaces its cells every week or so. All this metabolic activity makes the cells particularly vulnerable to damage. In some cases, that damage can result in cancer of the colon or rectum. Not counting skin cancer, colon and rectal cancers are the fourth most common form of cancer. Approximately fifty-six thousand people in the United States will die this year because of the disease, accounting for about 3 percent of all deaths.

While scientists do not know the exact cause of colorectal cancer, we do know that it is among the most preventable forms of cancer, even with people with a positive family history of this disease. Clearly diet plays a huge role. The typical American diet – high in fat, low in fiber from fruits and vegetables – is largely to blame. Fat takes longer to digest than other nutrients. Breaking down fat can cause a kind of residue to form in the intestine. This residue irritates cells and can cause them to become abnormal. What's more, as I have explained, fat triggers production of bile, and bile acids may further irritate and damage cells. Lack of fiber means all this bad stuff is not able to pass out of the intestine as fast as it should.

Colorectal cancer often begins when a polyp grows on the intestinal lining. A polyp is a mushroom-shaped clump of tissue. Most polyps are harmless, but a small percentage of them can become cancerous. Colorectal cancer may or may not cause symptoms. Your doctor can detect polyps through a procedure called a sigmoidoscopy, which uses a viewing scope to examine the lower part of the intestine, or a colonoscopy, which explores the whole organ. Often the polyp can be removed by snipping if off at the base. However, if many polyps are present, or if some of them appear to be progressing into cancer, it may be necessary to remove a section of the intestine through surgery.

Obviously, preventing colorectal cancer is the best way to go. The best strategy is to eat a healthy diet. Cut down on meat, protein, and animal fat. Avoid meat that has been fried, charcoal-grilled, or cooked at high temperatures; these forms of preparation produce high levels of cancer-causing compounds. Increase fiber intake by eating fruits, vegetables, and whole grains. Foods rich in calcium, vitamin C, and folate appear to offer protection. Calcium is of special interest, because it readily binds with irritants in colon and blocks their ability to stimulate cell proliferation. A recent study found that when people who had had polyps removed supplemented their diet with 1,200 mg of calcium a day, cell growth in the colon returned to normal.

A healthy lifestyle helps too. Drinking more than one or two alcoholic beverages especially beer a day appears to increase the risk, perhaps by encouraging cells to reproduce more rapidly and by damaging the new cells. Cigarette smoking may cause a high risk of polyps; in smokers, polyps are more likely to regrow after they have been removed. People who exercise throughout their lives and who maintain a healthy weight have a lower rate of colorectal cancer. Some evidence suggests that taking aspirin and other NSAIDs or, better yet, natural inhibitors of prostaglandin may help.