Age, family history, and more play a role in the development of the disease.

By Karen Pallarito
March 19, 2019

Don’t assume you couldn’t possibly develop colorectal cancer because you’re not old enough or you’re otherwise healthy unless you know your colorectal cancer risk factors.

“Basically everyone has some risk,” Jennifer Christie, MD, clinical director of gastroenterology at Emory Clinic in Atlanta, tells Health.

Colorectal cancer (or colon cancer, for short) starts in the lining of the colon (aka the large intestine) or the rectum. In women, the lifetime risk of developing this cancer is just over 4%; in men, it’s 4.5%, according to the American Cancer Society (ACS).

While it’s not always clear what causes colon cancer, there are certain risk factors that can boost your odds of developing this disease.

Risk factors help determine when someone should start screening and how often, so talk to your doctor about your particular colorectal cancer risks.

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Your age

Colorectal cancer is most frequently diagnosed in people 50 and older. But youth does not give you a pass.

“We’ve seen patients here as young as 17 with colon cancer, so it’s not always the cancer of older people,” observes Benjamin Weinberg, MD, assistant professor of medicine in the Division of Hematology and Oncology at Georgetown University’s Lombardi Comprehensive Cancer Center in Washington, D.C.

Most young adult colon cancers occur in people in their 40s, according to the Colorectal Cancer Alliance. Nobody really knows why younger folks are developing colon and rectal cancer, adds Dr. Weinberg, who is conducting research to explore whether a person’s gut microbiome might play a role.

In 2018, the ACS called for screening to begin at age 45, instead of 50, in people of average risk, based in part on rising rates of colon cancer in young adults.

Your race or ethnicity

African Americans are not only at higher risk of developing colon cancer; they’re more likely to die from it.

“We don’t know why that may be, but we do believe that there may be genetic factors,” notes Dr. Christie. “And there also may be some dietary factors that may be playing a role,” she says.

The American College of Gastroenterology recommends screening African American men and women beginning at age 45.

People of Ashkenazi Jewish descent have one of the highest risks of colon cancer of any ethnic group in the world.

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Family history

Anyone with an immediate family member (a parent, sibling, or child) or several second-degree relatives (grandparents, aunts, and uncles) with colon cancer is at higher risk of developing the disease.

If colorectal cancer runs in your family, your doctor will likely recommend that you begin screening at an earlier age than someone at average risk.

It’s not clear whether an inherited risk, such as family history, makes someone more susceptible than a lifestyle risk, like your diet, but each poses an independent risk, Dr. Weinberg explains.

Personal history

If you’ve had pre-cancerous growths (called polyps) removed from your colon or rectum, you’re more likely to develop colorectal cancer.

Certain non-colon cancers, such as uterine or ovarian cancer, may also raise your risk for colorectal cancer.

“You should make sure you get appropriate follow-up [care],” says Dr. Christie, a member of the governing board of the American Society for Gastrointestinal Endoscopy.

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A diagnosis of inflammatory bowel disease

People with the inflammatory bowel diseases Crohn’s disease or ulcerative colitis are at greater risk of developing colorectal cancer.

“Any time you have chronic inflammation, you have increased cell turnover. And every time a cell turns over, there’s a theoretical risk that it can develop a mutation,” explains Dr. Weinberg, a gastrointestinal oncology specialist.

Over time, he adds, some of these cellular defects can cause cancer.

An inherited syndrome

A number of different gene-based syndromes can boost your risk of developing colon cancer. Lynch syndrome is the most common hereditary cause of colon cancer. Another is familial adenomatous polyposis or FAP.

Of course, you might not know the genetics of your family’s colon cancer. “But if you have a cluster of colon cancers in your first-degree relatives or even a grandparent and then a cousin or aunt, then that sort of tells you something,” Dr. Christie says. “And that’s probably going to put you in the higher-risk category.”

RELATED: What Is Lynch Syndrome—and How Does It Increase Colon Cancer Risk?

A sedentary lifestyle

While there’s no proof that exercise actually lowers a person’s risk of colon cancer, studies show that folks who are inactive are much more likely to develop the disease than regular exercisers.

In fact, people who’ve previously had colon cancer removed are encouraged to exercise to reduce their risk of recurrence, Dr. Weinberg notes. “It doesn’t need to be running marathons,” he says. “It can even be just getting your heart rate up a few times a week.”

Certain dietary factors

What you eat can make a difference when it comes to your risk of colorectal cancer. A diet high in red meat and processed meat has been linked to higher rates of the disease.

Patients always ask Dr. Christie, “Doc, how can I reduce my risk? What should I eat?” In general, she says she recommends a high-fiber, low-fat diet, including plenty of green, leafy veggies.

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Being overweight or obese

Does a person’s weight affect colon cancer risk? “We think obesity may play a role, but we don’t change our screening recommendations based on somebody’s body mass,” Dr. Weinberg says.

It’s not just a high BMI that makes a difference. Carrying around excess belly fat is also linked to a higher risk of several different cancers, including colorectal cancer.

Drinking too much

Excess alcohol consumption is consistently linked to a higher risk of multiple cancers, including colorectal cancer, according to the American Society of Clinical Oncology.

To reduce this risk, women should limit their drinking to no more than one alcoholic beverage a day and men should stick to one to two drinks daily.

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Smoking

Tobacco use isn’t just toxic to the lungs. If you’re a longtime smoker, you’re more likely to die from colon cancer than a non-smoker, according to the ACS.

A large Norwegian study found women and men who had ever smoked had a 20% increased risk of death from colorectal cancer compared with people who had never smoked.

Having type 2 diabetes

Even after accounting for being overweight and sedentary, people with type 2 diabetes have a higher risk of developing colon cancer, according to the ACS.

Oftentimes, people who have diabetes have higher levels of insulin circulating in their blood, which may stimulate cancer growth, Dr. Christie notes.

Get more on colorectal cancer here.