Medical Health Encyclopedia

The risks for colon cancer are far higher in industrialized nations than less developed countries. A Western lifestyle, being sedentary, smoking, and excess weight have all been associated with increased risk for colorectal cancer. (It should be noted, however, that about 75% of cases occur without a known predisposing factor.)

Dietary Factors. Studies indicate that diets low in fruits and vegetables and high in meats pose a risk for colon cancer. Research also indicates that diets rich in fruits and vegetables are protective against many cancers.

Alcohol and Smoking. Smoking may increase the risk for colon cancer, and drinking alcohol regularly appears to compound this risk. Nonsmokers who drink alcohol and have diets rich in vegetables and fruits do not seem to have an increased risk.

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Obesity. There is a demonstrated link between body mass and colon cancer risk for both men and women. The Centers for Disease Control and Prevention has reported that the risk of colon cancer rises as body mass index (BMI) increases. Obesity has been associated biologically with higher circulating levels of insulin and a hormone called insulin-like growth factor (IGF). Chronically high levels of these substances may increase colorectal cancer risk.

Physical Inactivity. More than 50 studies from around the world suggest that physical activity helps prevent colon cancer. In contrast, exercise does not protect against rectal cancer.

Risk Factors for People with Inflammatory Bowel Disease

Crohn's disease and ulcerative colitis are chronic afflictions of the large intestine known as inflammatory bowel diseases (IBDs). Both have been linked to increased risk for colorectal cancer. Family histories are helpful in determining risk associated with inflammatory bowel disease. Some studies suggest the following:

• Patients with IBD who have a family history of colorectal cancer face up to a five-fold risk of colon cancer themselves.
• Individuals without IBD who have relatives who suffered from both IBD and colorectal cancer may face a higher risk for developing colorectal cancer themselves.
• Individuals without IBD but with a family history of IBD and no colon cancer most likely face no higher risk for cancer themselves.

Crohn's disease, also called regional enteritis, is a chronic inflammation of the intestines which is usually confined to the terminal portion of the small intestine, the ileum. Ulcerative colitis is a similar inflammation of the colon, or large intestine. These and other IBDs (inflammatory bowel disease) have been linked with an increased risk of colorectal cancer.

Other Risk Factors