It was a success story. Colorectal cancers dropped by 46 percent from 1985 to 2019. But rates are now rising in people under 55. And colorectal cancer will still kill 53,000 Americans in 2024—more than any cancer other than lung. Here’s the latest on how to lower your risk.

1. Eat a healthy diet with less red and processed meat.

“People who eat healthier diets have a lower risk of colorectal cancer,” says Heather Eliassen, professor of nutrition and epidemiology at the Harvard T.H. Chan School of Public Health.

The DASH (Dietary Approaches to Stop Hypertension) diet is one of those healthy ones. “It captures a higher intake of fruits and vegetables, whole grains, nuts, legumes, and low-fat dairy, and a lower intake of red and processed meat,” explains Eliassen.

“And in a study of women under 50, those who ate a DASH diet had a lower risk of colorectal polyps—precancerous growths—with a high malignant potential.”

Processed meats (like bacon, cold cuts, ham, hot dogs, and sausages) have the clearest link to cancer.

They’re “carcinogenic to humans,” says the International Agency for Research on Cancer. Unprocessed red meats (beef, pork, lamb, and veal) are “probably carcinogenic,” says IARC.

A daily 2 oz. serving of processed meat boosts colorectal cancer risk by 18 percent, estimates the agency.

To clarify how those meats boost risk, researchers gave people about 10 oz. a day of either processed red meat (ham and sausages) or unprocessed white meat (chicken or turkey) for two weeks each.

“We saw an increase in the excretion of potentially carcinogenic N-nitroso compounds after the consumption of the red meats,” explains Simone van Breda, assistant professor of toxicogenomics at Maastricht University in The Netherlands.

That confirms earlier studies, which reported that the heme in unprocessed red meat also spurs the carcinogens to form.

“We also saw an increase in DNA strand breaks and DNA adducts in colon cells after red meat consumption,” says van Breda. (An adduct forms when a chemical binds to DNA.)

“That’s damage on the DNA level. So these meats can cause mutations in DNA that can eventually lead to cancer.”

Van Breda’s study also tested processed red meats that contained extracts from plants like green tea, oregano, and sage. The extracts led to fewer N-nitroso compounds—but not fewer DNA breaks or adducts—than ordinary processed red meats.

Until more studies are done, “lower your intake of red meat and particularly processed red meat,” advises van Breda. “And if you eat meat, try to also eat more fruits and vegetables.”

2. Try eating more beans.

“The National Cancer Institute believes a high fiber, low fat diet may reduce your risk of some kinds of cancer,” declared a Kellogg’s All-Bran ad campaign in 1984.

But by 2000, four  trials had come up empty. A higher-fiber diet had no impact on polyps in people with earlier polyps. (One of the trials, partly funded by Kellogg, tested bran cereal.)

The largest study, the Polyp Prevention Trial, found no fewer polyps in roughly 1,000 people who were randomly assigned to eat 36 grams of fiber per day (from vegetables, fruit, beans, grains, etc.) than in nearly 1,000 others who ate their usual diet.

“But among those in either group who increased the legume content of their diet, there was a 65 percent lower risk of new advanced polyps,” says Terry Hartman, professor of epidemiology at Emory University.

That finding, which could have been due to chance, is far from proof that legumes—like lentils, garbanzos, and pinto beans—prevent cancer.

But it led Hartman and her colleagues to launch a new trial that will randomly assign 60 people with a previous polyp and excess weight to receive either two daily bean-rich or non-bean entrées (like chicken) for 3 months and then one entrée a day for 3 more months.

“The bean group will get about 1½ cups of legumes per day,” she notes. “That will put them over fiber levels recommended by the FDA.” Most Americans are well below those levels.

“We’re looking at changes in biomarkers of colorectal cancer risk measured in tissue biopsies,” explains Hartman. The biopsies will look at cell proliferation, inflammation, and apoptosis—the body’s process for getting rid of abnormal cells.

“We’ll also look at short-chain fatty acids like butyrate, which has anti-carcinogenic and anti-inflammatory properties,” adds Hartman.

And the study will track secondary bile acids, which may raise the risk of polyps.

It’s too early to know if beans can cut cancer risk. But when it comes to fiber-rich, unprocessed, inexpensive plant-based protein, you can’t beat beans. Bonus: Their soluble fiber lowers LDL (“bad”) cholesterol.

3. Beware of suspect additives in ultra-processed foods.

“Ultraprocessed foods linked to cancer and early death, studies find,” reported CNN.com in 2022, citing a new study on colorectal cancer.

The study reported a 29 percent higher risk of colorectal cancer in men who ate the most ultra-processed foods, especially “ready-to-eat” meats like hot dogs and sausages and sugary drinks. (The researchers saw no higher risk in women who ate ultra-processed foods.)

“Consuming ultra-processed food may change the bacteria in our gut, and that could cause inflammation or other factors that contribute to cancer risk,” says Fang Fang Zhang, associate professor of epidemiology at Tufts University, who led the study.

But something other than ultra-processed foods might also play a role. For example, in a recent study, people who eat more ultra-processed foods were also more likely to die of accidental causes like car crashes, suggesting that food may not entirely explain their higher risk of the disease.

“People who consume the most ultra-processed foods may also have an overall unhealthy lifestyle, and those behaviors, not ultra-processed foods, may increase the risk of cancer,” notes Zhang.

A few additives that are found in many ultra-processed foods have raised concerns:

Emulsifiers

Two emulsifiers—carboxymethylcellulose and polysorbate 80—cause low-grade gut inflammation in mice given high doses.

And in two out of 7 people given a high dose of carboxymethylcellulose for 11 days, gut bacteria encroached on the layers of mucus that ordinarily protect the intestinal lining from bacteria.

“We’re trying to understand why some people respond and others do not,” says Andrew Gewirtz, professor at the Institute for Biomedical Sciences at Georgia State University.

Titanium dioxide  

In May 2021, the European Food Safety Authority (the European Union’s FDA) decided that titanium dioxide was no longer safe to add to foods, in part because it might damage DNA. But the FDA still allows the additive, which brightens and whitens foods.

“In our mouse studies, titanium dioxide did not induce tumors by itself,” says Maastricht University’s Simone van Breda. “But in an inflamed colon, or in an animal that is vulnerable to developing tumors, titanium dioxide promoted the process of carcinogenesis.” That didn’t happen in all studies, though.

“We are now measuring inflammation, oxidative stress, and DNA damage in a human study,” says van Breda.

4.  Pick a good screening test.

“A blood test shows promise for early colon cancer detection,” reported the New York Times in March.

“Promise” is right. It’s too early to say how good the new Shield test (made by Guardant Health) is.

“The test is not yet FDA-approved,” says Timothy Wilt, director of the VA-Evidence Synthesis Program at the Minneapolis VA. “And it has some potential and some limits.”

On the upside, more symptom-free people are likely to get a blood test than a colonoscopy or a stool test.

“As the old adage says, the best screening test is the one that gets done,” says Jennifer Lin, director of the Kaiser Permanente Evidence-based Practice Center.

Other pluses: In the new (Guardant-funded) study, the blood test detected 83 percent of cancers seen in colonoscopies. And only 10 percent of the blood tests were false positives—that is, the test said the person had cancer but no cancers or precancerous lesions were seen in colonoscopies.

A key downside: The blood test detected only 13 percent of precancerous polyps seen in colonoscopies.

That said, “stool tests also have a low sensitivity to detect advanced polyps,” notes Lin, who reviewed screening tests for the U.S. Preventive Services Task Force (USPSTF).

The widely used fecal immunochemical tests (FIT) pick up 23 percent of polyps. (The tests use antibodies to detect blood in stool.)

In contrast, colonoscopies detect 89 percent of large—and 75 percent of small—polyps. But many symptom-free people don’t get them.

Guardant’s new study looks promising, says Lin, “but it’s just one study, whereas we have many large cohort studies demonstrating that the FIT test and colonoscopy actually decrease colorectal cancer or deaths from the cancer.”

However, “if the evidence continues to accrue for the new blood test, it would be a game changer,” adds Lin.

Until then, here’s what to consider.

Colonoscopy or FIT stool test

They’re backed by the best evidence, say the U.S. Multi-Society Task Force on Colorectal Cancer (gastroenterologists) and the American College of Physicians (internists).

“For folks who have a higher-than-average risk, a colonoscopy is the best option,” says Lin. It’s clearly the best way to detect precancerous polyps.

“Average” risk means you have no symptoms, no previous diagnosis of colorectal cancer, polyps, or inflammatory bowel disease, and no diagnosis or family history of a genetic disorder that raises the risk of colorectal cancer, says the USPSTF.

If your risk is average, take your pick.

“I have patients who say, ‘I never want to get a colonoscopy if at all possible, so give me the least invasive thing, and I’m happy to do it yearly,’” says Lin. “Other patients say, ‘I don’t want to mess with my poop or do a test yearly. Just let me do a colonoscopy every 10 years.’”

The USPSTF also endorses two other tests:

Stool DNA-FIT test

“We’re the only noninvasive screening test that looks for both abnormal DNA and blood in your stool,” says Cologuard’s website. The test finds more cancers (93 percent) than a FIT test alone (74 percent) and more advanced polyps (43 percent). But it also finds more false positives for cancers (15 percent) than a FIT test alone (6 percent).

“And the cost of a stool DNA test every three years is about $1,500, versus about $100 for a FIT test,” notes Wilt. (Medicare and most insurance plans cover the higher cost.)

Colonography

With a computed tomography colonography (CTC), you have to do the same bowel-cleansing prep needed for a colonoscopy. But instead of using a scope to examine your colon, a CTC takes low-dose x-rays of your abdomen.

“And if the scan finds something, you still have to get a colonoscopy,” says Wilt. “So it adds a costly step and exposure to radiation. And if the scan finds something outside the colon, that can lead you down a rabbit hole.”

Colorectal cancer symptoms

5. Know when to get screened...and don't ignore symptoms.

“45 is the new 50!” says the American College of Gastroenterology.

People at average risk should start screening for colorectal cancer at age 45, not 50, said the USPSTF in 2021. The American Cancer Society and U.S. Multi-Society Task Force on Colorectal Cancer agree.

“Cancers diagnosed before age 50 have increased over time,” notes Lin.

Why? “Lifestyle factors like diabetes, obesity, and unhealthy diets have been heading in the wrong direction for some time, so that can certainly account for some of the increase.”

A sedentary lifestyle and alcohol (two or more drinks a day) may also play a role. Alcohol is “carcinogenic to humans,” says the International Agency for Research on Cancer. The body converts it to acetaldehyde, which can damage DNA. Alcohol may also allow microbes to penetrate the gut lining, causing inflammation.

However, “I don’t think the scientific community has a good understanding of why we’re seeing more cancer in younger age groups,” notes Lin.

And their cancers are more likely to have spread to lymph nodes or to organs like the liver or lungs.

Unlike the USPSTF, the American College of Physicians recommends that “clinicians should consider not screening” people aged 45 to 49.

Why? “Their risk of having colon cancer before the age of 50 is less than one in 1,000,” says Wilt, who chaired the group’s clinical guidelines committee, which issued the advice. “Age is by far the biggest risk factor.”

Plus, “there are already extensive waiting lists for colonoscopies.” And anyone who tests positive on a stool or blood test or CTC would need one.

“More routine testing will increase costs,” adds Wilt. “We should focus our resources on people who are at higher risk and not yet getting screened. That’s adults 55 to 75, and we’re only screening about 65 to 70 percent of them now.”

He tells patients aged 45 to 49 about their low risk and suggests they consider not screening. “If they say, ‘Doc, I’d still like to be screened,’ I do it,” says Wilt.

He’s talking about people without symptoms. Younger patients are more likely to report abdominal pain and rectal bleeding than older people, possibly because cancers in younger adults occur more often in the rectum than in older people.

Don’t ignore—or let your doctor brush off—those or other symptoms, whatever your age.

When should average-risk people stop screening? After age 85, says the USPSTF. If you’re 76 to 85, the decision depends on your health, past screening, and preferences.

“If somebody who has been regularly screened turns 75, there is almost zero benefit in extending screening,” says Wilt.

“And if you find a polyp and remove it, people over 75 have an increased risk of perforation or bleeding.”

“If my patients did a FIT test every year, or had a colonoscopy that found no polyps at 65, I’ll say, ‘This is the last one we’re gonna need. Let’s focus on other things.’ But if a patient says, ‘Doc, I’d still like to get screened,’ I’ll screen them.”