Colorectal Cancer Risk Factors

What is a risk factor?  

A colorectal cancer (bowel cancer) risk factor is something that increases the chance of developing colon cancer and rectal cancer. Having a risk factor, or even several risk factors, does not mean a person will certainly get the disease. And people can still develop colorectal cancer (CRC) without having any known risk factors.

Some risk factors are things you can change, such as lifestyle factors like diet, physical activity, or smoking. Other risk factors are non-modifiable, like age, race and ethnicity, or family history of colorectal cancer.  

What are the risk factors for colorectal cancer?

• age - the risk of cancer increases with age, 90% of CRC occurs in people over age 50 though recent trends reflect an increase in the incidence of early-onset CRC, before age 50
• race or ethnicity - African Americans and Ashkenazi Jews are at higher risk for colorectal cancer
• diet - eating a diet that is low in fruits, vegetables, and fiber or a diet that is high in fat and processed meats is associated with a higher risk of colon cancer
• tobacco use - smoking is associated with an increased risk
• drinking alcohol (alcohol consumption)
• physical inactivity (lack of regular exercise)
• overweight and obesity
• previous colon polyps or rectal polyps (adenomas)
• inflammatory bowel disease (ulcerative colitis, Crohn's disease, IBD)
• personal history of previous colorectal cancer, endometrial (uterine) cancer, breast cancer, or ovarian cancer  
• genetic syndromes of increased risk of colorectal cancer - this includes Lynch syndrome, also known as hereditary non-polyposis colorectal cancer (HNPCC), which is associated with several other types of cancer, and familial adenomatous polyposis (FAP), a genetic syndrome characterized by high risk of colorectal polyps occurring at a younger age (starting in the teenage years)  
• family members with a history of colorectal cancer
• family members with a genetic cancer syndrome like Lynch syndrome or familial adenomatous polyposis

People with an average risk of colorectal cancer, about 5% lifetime risk, do not have a personal or family history of colorectal polyps or colorectal cancer, do not have inflammatory bowel disease, and have no history that suggests a possible hereditary cancer syndrome like a past history of endometrial, breast, or ovarian cancer.

How can I lower my risk of colorectal cancer?

While taking steps to prevent colorectal cancer through lifestyle and dietary changes can make a difference, the most effective method of prevention for both men and women is to receive regular colorectal cancer screening.  

Almost all colorectal cancers begin as precancerous polyps (abnormal growths) in the colon or rectum. Precancerous colorectal polyps are also called colorectal adenomas, and they can be removed by colonoscopy. These polyps can be present in the colon for years before they become cancerous tumors. They may not cause any symptoms. Colorectal cancer screening tests can help find precancerous polyps so they can be removed before they turn into cancer, dramatically reducing your risk of developing or dying from colorectal cancer.  

Medical experts don't agree on the role of diet in colorectal cancer prevention, but often recommend a diet high in fruits, vegetables, and whole grains and low in animal fats to reduce the risk of other illnesses, such as heart disease and type 2 diabetes. This diet may also reduce the risk of colorectal cancer. Also, researchers are studying the role of certain medicines and dietary supplements in preventing colorectal cancer.

Dietary and lifestyle choices that may help prevent CRC include:  

• Exercising regularly
• Maintaining a healthy weight
• Reducing alcohol consumption
• Increasing dietary fiber
• Quitting smoking
• Reducing red meat and processed meat consumption
• Increasing calcium and vitamin D intake
• Eating more foods with polyphenols (compounds often found in fruits, vegetables, and nuts)