Colorectal Cancer: Risk Factors and Prevention

Approved by the Cancer.Net Editorial Board, 09/2023

ON THIS PAGE: You will find out more about the factors that increase the chance of developing colorectal cancer. Use the menu to see other pages.

What are the risk factors for colorectal cancer?

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. 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% to 10%) and occur when gene mutations, or changes, are passed within a family from 1 generation to the next (see below). Up to 30% of colorectal cancers are diagnosed in people with a family history of colon or rectal cancer but without a known inherited condition (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 the majority of colorectal cancers occur in people older than 50. For colon cancer, the average age at the time of diagnosis for men is 66 and for women is 69. For rectal cancer, it is age 62 for men and 63 for women. Adults 65 and older who are diagnosed with colorectal cancer face unique challenges, specifically with regard to cancer treatment. Learn more about aging and cancer.

    It is important to note that while colorectal cancer is still diagnosed most commonly in older adults, the incidence rate for colorectal cancer declined by about 3.6% per year in adults 55 and older, based on the latest statistics. Meanwhile, the incidence rate increased by 2% per year in adults younger than 55. The increase is due in large part to rising numbers of rectal cancer. About 20% of all colorectal diagnoses are in people under age 55. The reason for this rise in younger adults is not well known and is an active area of research.

  • 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 death 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.

  • Sex. 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, their risk of developing the disease is nearly double. 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.

    About 5% to 10% of cases of colorectal cancer are associated with inherited genetic mutations that increase the risk of cancer and affect the way that the cancer is treated. This is why your doctor may recommend evaluation for inherited mutations if you have been diagnosed with colorectal cancer. Evaluation may include review of personal and family histories of cancer and molecular testing of tumor tissue.

    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 before you have any genetic testing. Only genetic testing can find out if you have a genetic mutation, and genetic counselors are trained to explain the risks and benefits of genetic testing.

  • Rare inherited conditions.Members of families with certain uncommon inherited conditions have a higher risk of colorectal cancer, as well as other types of cancer. These include:

  • 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 Screening).

  • Personal history of certain types of cancer. People with a personal history of colorectal cancer previously or a diagnosis of ovarian cancer or uterine cancer are more likely to develop colorectal cancer.

  • Physical inactivity and obesity. An inactive lifestyle, meaning no regular exercise and a lot of sitting, and being overweight or obese may increase a person's risk of colorectal cancer.

  • Food/diet. Current research consistently links eating more red meat and processed meat to a higher risk of the disease. Other dietary factors have also been studied to see if they affect the risk of developing colorectal cancer, but the data are less consistent on which diets or foods change a person's risk of colorectal cancer.

  • Smoking. Recent studies have shown that people who smoke are more likely to die from colorectal cancer than those who do not smoke. Learn more about quitting tobacco use.

  • Diabetes. Studies have shown that people with type 2 diabetes have an increased risk for colorectal cancer.

Are there ways to prevent colorectal cancer?

Different factors cause different types of cancer. Researchers continue to look into what factors cause colorectal cancer, including ways to prevent it. Although there is no proven way to completely prevent colorectal cancer, you may be able to lower your risk. Talk with your health care team for more information about your personal risk of colorectal cancer.

As explained above, polyp removal during a colonoscopy (see Screening) can help prevent colorectal cancer. This procedure allows the doctor to look inside the large intestine to look for and remove polyps that could turn into cancer.

The following may also 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 aspirin or 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 is 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.

  • Managing your body weight. There is evidence that links higher body weight with a higher risk of developing colorectal cancer. Eating well is one of the best ways to improve your health and lower your cancer risk. This can help you maintain your body weight or lose weight if necessary.

  • Being physically active. Being physically active can lower your risk of colorectal cancer. The American Cancer Society recommends that adults should get 150 to 300 minutes of moderate-intensity physical activity per week or 75 to 150 minutes of vigorous-intensity physical activity, or a combination of these. Getting to 300 minutes or more is best. Children and teens should get at least 1 hour of moderate- or vigorous-intensity activity every day. Try to reduce the amount of sedentary behavior in your daily life, such as sitting, lying down, and watching television and other screen-based entertainment.

  • Managing your food choices. Eating patterns that are 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.

Learn more about cancer prevention and healthy living.

The next section in this guide is Screening. It explains how tests may find colorectal cancer before signs or symptoms appear. Use the menu to choose a different section to read in this guide.