Causes and risk factors
Like most types of cancer, colon cancer is most common in older people. Over 80% of colon cancers are diagnosed in people over 60.
The exact cause of colon cancer is unknown, though there are risk factors that can increase the likelihood of developing this type of cancer. Just because someone has a risk factor does not mean they will have cancer, and not having a risk factor does not mean they will not develop cancer.
Diets that are high in red and processed means increase the risk of colon cancer. Eating fried foods or grilled meats can increase the risk.
Not eating enough fresh fruits and vegetables can also increase the risk.
Lack of physical activity
People who are not physically active are more likely to develop colon cancer.
Excess weight may increase the risk of developing cancer of the colon, especially in men.
Smoking increases the risk of colon cancer. The longer you smoke and the more cigarettes you consume, the greater the risk.
Inflammatory bowel conditions
Having an inflammatory bowel condition, such as ulcerative colitis or Crohn's disease, can increase the risk of developing colon cancer. People who have these conditions can participate in regular screening programs with colonoscopies.
Irritable bowel syndrome is not an inflammatory condition of the intestines and does not increase risk of developing cancer of the colon.
Most people who have colon cancer have no family history of the disease. Having a family member who developed colon cancer at an older age does not increase your risk significantly. However, if several members of your close family have had colon cancer or if a member of your close family developed the disease before age 50 may indicate a higher risk. Your close family members include your parents and siblings.
Around 5% of cancers of the intestines are caused by an inherited genetic defect.
Two conditions may be associated with hereditary predisposition: familial adenomatous polyposis (FAP) and Lynch syndrome.
People who have either of these two conditions have a very high risk of developing colon cancer.
Familial adenomatous polyposis (FAP)
People with FAP have many benign tumors (polyps) in the lining of their colon and rectum.
It is usually recommended that people with FAP have surgery to remove the colon and, in some cases, the rectum.
Unless the colon is removed, almost everyone with FAP will develop colon cancer.
FAP causes about 1% of all colon cancers.
People who have Lynch syndrome are at greater risk of developing cancer of the colon at a young age. If you have Lynch syndrome, you will probably have regular tests performed using colonoscopy.
Lynch syndrome causes about 3% of all colon cancers.