Colorectal Cancer: Risk Factors and Prevention

Approved by the Cancer.Net Editorial Board, 06/2016

ON THIS PAGE: You will find out more about the factors that increase the chance of developing this type of cancer. To see other pages, use the menu.

A risk factor is anything that increases a person’s chance of developing cancer. Although risk factors often influence the development of cancer, most do not directly cause cancer. Some people with several risk factors never develop cancer, while others with no known risk factors do. However, knowing your risk factors and talking about them with your doctor may help you make more informed lifestyle and health care choices.

A person with an average risk of colorectal cancer has about a 5% chance of developing colorectal cancer overall. Generally, most colorectal cancers (about 95%) are considered sporadic, meaning the genetic changes develop by chance after a person is born, so there is no risk of passing these genetic changes on to one’s children. Inherited colorectal cancers are less common (about 5%) and occur when gene mutations, or changes, are passed within a family from 1 generation to the next (see below). Often, the cause of colorectal cancer is not known. However, the following factors may raise a person’s risk of developing colorectal cancer:

  • Age. The risk of colorectal cancer increases as people get older. Colorectal cancer can occur in young adults and teenagers, but more than 90% of colorectal cancers occur in people older than 50. The average age of people diagnosed with colorectal cancer in the United States is 72.

  • Gender. Men have a slightly higher risk of developing colorectal cancer than women.

  • Family history of colorectal cancer. Colorectal cancer may run in the family if first-degree relatives (parents, brothers, sisters, children) or many other family members (grandparents, aunts, uncles, nieces, nephews, grandchildren, cousins) have had colorectal cancer. This is especially true when family members are diagnosed with colorectal cancer before age 60. If a person has a family history of colorectal cancer, his or her risk of developing the disease is nearly double the average risk of colorectal cancer. The risk further increases if other close relatives have also developed colorectal cancer or if a first-degree relative was diagnosed at a younger age.

It is important to talk to your family members about your family’s history of colorectal cancer. If you think you may have a family history of colorectal cancer, talk with a genetic counselor first before you have any genetic testing. Only genetic testing can determine if you have a genetic mutation, and genetic counselors are trained to explain the risks and benefits of genetic testing.

  • Inflammatory bowel disease (IBD). People with IBD, such as ulcerative colitis or Crohn’s disease, may develop chronic inflammation of the large intestine. This increases the risk of colorectal cancer. IBD is not the same as irritable bowel syndrome (IBS). IBS does not increase your risk of colorectal cancer.

  • Adenomatous polyps (adenomas). Polyps are not cancer, but some types of polyps called adenomas can develop into colorectal cancer over time. Polyps can often be completely removed using a tool during a colonoscopy, a test in which a doctor looks into the colon using a lighted tube after the patient has been sedated. Polyp removal can prevent colorectal cancer. People who have had adenomas have a greater risk of additional polyps and of colorectal cancer, and they should have follow-up screening tests regularly (see below.)

  • Personal history of certain types of cancer. People with a personal history of colorectal cancer and women who have had ovarian cancer or uterine cancer are more likely to develop colorectal cancer themselves.

  • Race. Black people have the highest rates of sporadic, or non-hereditary, colorectal cancer in the United States. Colorectal cancer is also a leading cause of cancer-related deaths among black people. Black women are more likely to die from colorectal cancer than women from any other racial group, and black men are even more likely to die from colorectal cancer than black women. The reasons for these differences are unclear. Because black people are more likely to be diagnosed with colorectal cancer at a younger age, the American College of Gastroenterology suggests that black people begin screening with colonoscopies at age 45 (see Screening). Earlier screening may find changes in the colon at a point when they are more easily treated.

  • Physical inactivity and obesity. People who lead an inactive lifestyle, meaning no regular exercise and a lot of sitting, and people who are overweight and obese may have an increased risk of colorectal cancer.

  • Nutrition. Current research consistently links eating more red meat and processed meat to a higher risk of the disease. Other dietary factors have also been looked at to see if they affect the risk of developing colorectal cancer.

  • Smoking. Recent studies have shown that smokers are more likely to die from colorectal cancer than nonsmokers.


Different factors cause different types of cancer. Researchers continue to look into what factors cause this type of cancer. Although there is no proven way to completely prevent this disease, you may be able to lower your risk. Talk with your doctor for more information about your personal risk of colorectal cancer.

The following may lower a person’s risk of colorectal cancer:

  • Aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs). Some studies suggest that aspirin and other NSAIDs may reduce the development of polyps in people with a history of colorectal cancer or polyps. However, regular use of NSAIDs may cause major side effects, including bleeding of the stomach lining and blood clots leading to stroke or heart attack. Taking aspirin or other NSAIDs are not a substitute for having regular colorectal cancer screenings. People should talk with their doctor about the risks and benefits of taking aspirin on a regular basis.

  • Diet and supplements. A diet rich in fruits and vegetables and low in red meat may help reduce the risk of colorectal cancer. Some studies have also found that people who take calcium and vitamin D supplements have a lower risk of colorectal cancer.

The next section in this guide is Screening. It explains how tests may find cancer before signs or symptoms appear. Or, use the menu to choose another section to continue reading this guide.