What you need to know about colorectal cancer screenings, prevention and risk

Close-up of a middle-aged woman smiling and wearing a yellow shirt.


Colonoscopy screenings can prevent cancer, and healthy lifestyle choices can lower colorectal cancer risk.


By Dr. Steven Gorelick, System Chair of the Digestive Health Institute, Nuvance Health


If you are like most people, you might feel uncomfortable talking about colorectal health — even with your doctor. The truth is your colon, or the large intestine, is a critical part of your digestive system, important to your overall health and well-being, and worth talking about — especially now when colorectal cancer is increasing in younger people.


Here are answers to common questions about colorectal cancer, colonoscopy screenings, prevention and reducing risk.



What is colorectal cancer?


Colorectal cancer starts in the colon (colon cancer) or rectum (rectal cancer). Cancer develops when cells in your colon or rectum grow out of control. It begins as a growth in the lining of the colon or rectum called a polyp. If left untreated, some polyps can turn into cancer.


How common is colorectal cancer?


Besides some types of skin cancer, colorectal cancer is the third most common cancer in the United States. It is also one of the most preventable cancers because of colonoscopy screenings.


Adults at average risk of colorectal cancer should start screening colonoscopies at age 45, according to the United States Preventive Services Task Force. These guidelines are working! Colorectal cancer rates in people aged 50 and older have decreased since the mid-1980s.


However, colorectal cancer is the No. 1 cause of cancer deaths in men and No. 2 in women under age 50, according to an American Cancer Society 2024 report. Keep reading to find out how to lower your risk of colorectal cancer at any age, especially for people under the screening colonoscopy age.



What is a colorectal cancer screening test?


A colonoscopy screening is a procedure to see inside the colon. Screening is for people who do not have symptoms but is a proactive way to detect possible health concerns and address them early.


Doctors who specialize in gastroenterology perform colonoscopies using a thin, flexible tube with a tiny light and video camera at the end of it, called a colonoscope. This same-day, or outpatient, procedure usually takes about 15 to 30 minutes on average.


You must complete a bowel prep before having a colonoscopy. Different kinds of prep may include eating a special diet and drinking a liquid laxative a day or more before the procedure. Prep is important because it cleans out the colon so your doctor can clearly see the inside during the procedure.



During the procedure, the doctor inserts the colonoscope into the anus and then guides it through the rectum and colon to look for changes or irregularities, such as precancerous polyps. This occurs while you are comfortable and sedated throughout the procedure.


At what age should you get a screening colonoscopy?


People at average risk for colorectal cancer should start having colonoscopy screenings at age 45.


People who have a family history of colorectal cancer or other risk factors may need to start screenings earlier. If a first-degree relative had a polyp removed or colorectal cancer, you should start screenings when you are 10 years younger than they were at that time. For example, if your mom, dad or sibling was 42 when they had a polyp removed or colorectal cancer diagnosed, speak with your doctor about starting screenings when you are 32.



Read on to understand other risk factors that may prompt your doctor to recommend starting screenings sooner.



What causes colorectal cancer?


Colorectal cancer can occur to anyone at any age, although risk increases with age. Risk factors are conditions or habits that may increase the chances of getting a disease like cancer. 


If you have no known hereditary or family risk factors and follow a healthy lifestyle, you most likely have an average risk of developing colorectal cancer. If you have a genetic predisposition or certain lifestyle habits, such as smoking, you might have an elevated risk of developing colorectal cancer. Speak with your primary care provider to determine your risk of developing colorectal cancer. Some risk factors you cannot control, like your age, while others you can change to reduce risk, such as diet.



Who is most at risk for colorectal cancer?


Here are factors associated with an increased risk of colorectal cancer you cannot change:


  • Family health history: First-degree relative (parent, sibling or child) who had colorectal cancer or precancerous polyps.

  • Personal history: Inflammatory bowel disease, personal history of colorectal cancer or polyps, or genetic predisposition to colorectal cancer such as Lynch syndrome.

  • Ethnicity and race: People from Ashkenazi Jewish or African-American descent are at increased risk for colorectal cancer.


Even though you cannot change these factors, you can take other steps to reduce your risk of developing colorectal cancer, such as screenings and lifestyle modifications.



Here are lifestyle factors associated with an increased risk of colorectal cancer you can change:


  • Diet: Eating an unhealthy diet high in fats, salt, sugar and processed foods.

  • Exercise: Being sedentary or inactive.

  • Moderate to heavy alcohol use: According to the Dietary Guidelines for Americans, moderate alcohol consumption is defined as having up to one drink per day for women and up to two drinks per day for men; heavy alcohol use is defined as consuming eight drinks or more per week for women, and 15 drinks or more per week for men.

  • Smoking tobacco

  • Unhealthy weight: Being overweight or obese


Can you prevent colorectal cancer?


A colonoscopy is a preventive screening because the doctor can remove precancerous polyps during the exam before they have a chance to turn into cancer. Your doctor can also detect cancer early before it causes symptoms and is more treatable.


Start routine colonoscopy screenings at age 45 if you do not have a personal or family history that increases your risk for colorectal cancer.


Share your personal and family health history with your doctor to determine your potential hereditary risk for colorectal cancer. Your doctor may recommend you start colonoscopy screenings before age 45 depending on this information.


Consider the lifestyle factors you can change to reduce your risk of developing colorectal cancer. Speak with your doctor if you need support or resources to follow a healthy diet, get regular exercise or quit smoking. The good news: These lifestyle modifications can also reduce your risk of developing other types of cancer, diabetes, heart disease and obesity.



Is there an alternative to a colonoscopy screening?


We recommend colonoscopy screenings for most people because we can remove precancerous polyps and prevent colorectal cancer. However, we understand some people may not want to have a colonoscopy because they cannot tolerate the prep or for other reasons.


The most important thing is to find a screening test that works well for you rather than not have them at all. There are at-home stool sample tests available by prescription. These tests may be able to detect colorectal cancer early, but they cannot prevent it from developing. If a stool sample test has an abnormal result, you most likely will need a colonoscopy anyway to investigate further.



Why is colorectal cancer increasing in young adults?


Colorectal cancer screenings are not recommended for people at an average risk younger than 45. However, younger adults can also get it, and colorectal cancer in younger adults is on the rise in the United States.



Follow a healthy lifestyle, pay attention to unusual symptoms and see your doctor if you have:

  • A change in bowel habits, such as constipation or diarrhea that lasts for more than a few days

  • A feeling you need to have a bowel movement that is not relieved by having one

  • Rectal bleeding with bright red blood

  • Blood in the stool, which might make the stool look dark brown or black

  • Cramping or abdominal (belly) pain

  • Weakness and fatigue

  • Unintended weight loss



The bottom line: Colonoscopy screenings can prevent colon or rectal cancer from developing or detect it early when it is more treatable. Take control of your health by following a healthy lifestyle to reduce your chances of getting colorectal cancer. Talk with your doctor about your risk factors to determine when you should start colonoscopy screenings.