Does long-distance running cause colorectal cancer?

Apr 16, 2026

Key takeaways

A study published by the American Society of Clinical Oncology revealed a link between long-distance running and an increased risk of colorectal cancer.
About half of the participants had polyps and 15% had advanced adenomas, nearly tripling the rate of advanced adenomas among the general population (4.5%-6%).
There is no evidence that definitively shows running causes polyps, and physical activity is proven to lower your cancer risk.

An exercise designed to test your endurance, agility and discipline, marathons are one of the most celebrated physical activities. But a study published by the American Society of Clinical Oncology is sparking conversation by suggesting ultra-runners may have a higher chance of developing colorectal cancer.

Does this mean marathons and other long distance runs cause cancer? Not necessarily—but the data raise important questions.

First, what’s the deal with colorectal cancer?

Colorectal cancer has historically been typical for people aged 50 or older. However, young-onset colorectal cancer has been on the rise overall in the past several years.

In 2021, the U.S. Preventive Services Task Force lowered the recommended screening age from 50 to 45. Earlier this year, colorectal cancer was named the leading cause of cancer-related deaths in U.S. adults under 50.

What did the study find?

Dr. Timothy Cannon and his colleagues at Inova Schar Cancer in Fairfax, Va., presented their findings at the 2025 American Society of Clinical Oncology (ASCO) annual meeting.

Dr. Cannon, an oncologist, recruited 100 runners to undergo colonoscopies. The study looked at runners ages 35 to 50, who had either completed at least five marathons or two ultramarathons (any runs of 50 kilometers or more).

About half of the participants in the study had polyps, which can become cancerous, and 15% had advanced adenomas, which are likely to become cancerous.

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The rate of advanced adenomas among the general population of people of screening age is anywhere from 4.5%-6%, according to recent studies. The study done on marathon runners and ultrarunners nearly had a rate nearly triple those numbers.

What do these results mean?

Although these numbers seem extreme, the study shows a correlation, which is a trending relationship between long-distance running and advanced adenomas, not causation, meaning running directly causes the adenomas. There is no evidence presented that definitively shows running causes polyps.

It’s also important to note that adenomas are not cancer. According to Yale Medicine, only an estimated 5% to 10% of adenomas may eventually progress to become cancer. During a colonoscopy, your doctor can identify and remove adenomas and other polyps before they have the chance to become cancerous, making the screening an important preventive tool.

Why might extreme running influence colon health?

Runners put their bodies through a lot—and endurance runners frequently push themselves for long periods of time. One side effect of this could be chronic inflammation, which can lead to repeated cycles of cell damage and repair, providing an opportunity for mutations to happen and cancerous cells to grow.

Dietary habits of endurance runners can also affect their risk for colon cancer. According to Healthline, running one mile will burn an estimated 100 calories. To replenish nutrients, runners often opt for high caloric foods for immediate energy, which can slow down your digestion and impact your overall colon health.

Another possible link between running and colorectal cancer diagnoses could be runners missing common warning signs and symptoms—or rather, mistaking them for normal wear and tear on their bodies. If you experience any abnormal bowel or stomach issues, such as bleeding, diarrhea, constipation, or a change in your bowels that lasts more than a few days, talk to your health care provider.

How can I reduce my risk of colon cancer?

این screening age for colorectal cancer starts at 45 for people at average risk and should be done every 10 years (if previous results are typical). You may be considered at increased risk if you have:

A personal history of inflammatory bowel disease (such as ulcerative colitis or Crohn’s disease)

A personal or family history of colorectal cancer or certain kinds of polyps (adenomatous or “flat” polyps)

Hereditary colorectal cancer syndrome (such as familial adenomatous polyposis [FAP] or Lynch syndrome)

You may also be at an increased risk if you smoke, drink alcohol in excess, eat a lot of red or processed meats, or are overweight. If you’re at increased risk for colorectal cancer, you may need to start routine screening at an earlier age and/or be screened more often.

To prevent colorectal or detect it early, you can get a colonoscopy, during which your doctor can screen for cancer و can remove pre-cancerous polyps, making it preventive against cancer, too.

There are also other methods to screen for colorectal cancer, some of which are at-home tests. Abnormal results on one of those tests would require a follow-up colonoscopy.

Making healthy lifestyle choices can also reduce your risk of developing colorectal cancer. Eat lots of fruits and veggies, limit your alcohol and red meat intake, avoid using tobacco products entirely and eating processed meats, and get your daily exercise in.

Exercise—and running—is still good for you!

Although any extreme activity can have impacts on your body, it’s important to remember the overall benefits of exercise and movements. Exercise is proven to lower your cancer risk and improve health outcomes. Getting at least 30 minutes of exercise 5 days a week can drastically improve your health.

Physical activity is linked to a lower risk of not only colorectal cancer, but also breast and endometrial cancers, and there is some evidence that also links it to reducing the risk of other cancers. Including exercise as part of your routine can reduce stress, increase energy, boost your immune system, control your weight and reduce your risk of cancer.

For more information on how to reduce your risk of cancer, head to preventancer.org/ways-to-prevent.