Marathons may worsen health: scientists have discovered a worrying link to bowel cancer

Three young, slim, and very active people should not have any serious health problems, in theory. Two regularly ran 160 km ultramarathons, and the third completed 13 half-marathons in just one year.

But when they consulted oncologist Tim Cannon at the clinic... Inova Schar Cancer Center In Virginia, all three were diagnosed with advanced colon cancer. The oldest patient was only 40 years old. They had no known risk factors. The doctor began to suspect that extreme running could have been the trigger, according to the publication The New York Times.

What did the study show?

Dr. Cannon invited 100 marathon and ultramarathon runners aged 35 to 50 to undergo a colonoscopy.

The results were stunning:

• almost half of the participants were found to have polyps;
• In 15% of cases, there are high-grade adenomas that can develop into cancer.

For comparison: among people around 50 years old in the general population, such formations occur in only 4.5–6% of cases. Even among native Alaskans, who are genetically more prone to colon cancer, this figure is around 12%.

The research was presented at the American Society of Clinical Oncology conference, but has not yet been published in a peer-reviewed journal.

The runners' reaction

"I was shocked—running is supposed to be very good for your health," admits 47-year-old Laura Linville of Alexandria, Virginia, who participated in the study. She was found to have seven polyps, some of which had to be removed separately.

Despite this, the woman does not plan to give up marathons, but will now be regularly screened for colon cancer.

A worrying trend.

This study fits into a broader context: in recent years, there has been an increase in cases of colorectal cancer among people under 50, although this age was previously considered a low-risk age.

It is because of this trend that the recommended age for the first colonoscopy in the United States was lowered from 50 to 45 years in 2021.

The reasons for the rising incidence of the disease in young people remain a mystery. Doctors usually blame sedentary lifestyles and obesity. That's why the cases in highly trained, thin runners caught Cannon's attention.

"I don't want to give people a reason not to exercise, because the much bigger problem is a lack of physical activity," says the oncologist. "But, given what I've seen, I believe that extreme physical exertion may increase the risk of developing this type of cancer."