A recent study from the Inova Schar Cancer Institute in Fairfax, Virginia suggests a possible connection between intense endurance exercise and a higher risk of advanced colon cancer in younger adults.
Dr. Tim Cannon, a medical oncologist, shared insights with WTOP after studying several young endurance runners—specifically those under 40 who were diagnosed with advanced colon cancer. He speculated that the prolonged strain on the digestive system during long-distance running might lead to mutations that could cause cancer.
The research involved 100 adults aged 35 to 50 who had participated in five or more marathons or two or more ultramarathons. It showed that about 15% had advanced adenomas, precancerous lesions, which is notably higher than the usual 1% to 2% found in non-runners of that age. Additionally, 41% of the group had at least one adenoma.
Cannon pointed out, “The normal risk in the 35 to 50 population would be one-fifth of those numbers.” The average age of participants was about 42.5, which is significantly earlier than the recommended age of 45 for the first screening colonoscopy.
“The reason we all get colonoscopies, or we should all get colonoscopies, when we turn 45, is because if we remove a polyp or adenoma before it becomes cancerous, then we’re likely going to be safe from cancer,” he explained.
An often-ignored warning sign for endurance athletes
Cannon noted that many long-distance runners, as well as their doctors, tend to downplay the issue of bleeding after a run.
“It’s very common among long-distance runners, and it’s often been referred to as ‘runner’s colitis,’” he said, adding that the colloquial term is “runner’s trots.” He further mentioned that this condition has often been dismissed as harmless, leading some runners to believe that bleeding is a normal occurrence.
“People have assumed that ‘runner’s colitis’ is a benign entity, so they’ve been saying, ‘It’s normal for runners to bleed.’ And the reason I know this is because that’s what these runners who have cancer are telling me,” he stated.
Cannon urged that any presence of blood in stool, whether in runners or others, warrants medical attention.
“The most common presenting symptom for someone with colon cancer is blood in their stool. That’s how we often discover polyps or cancer,” he added.
While further research is being conducted to explore this potential link, Cannon acknowledged that other factors might also contribute to the increased colon cancer risk among extreme endurance athletes. “It could be the runners’ diets. There might be lifestyle habits they share or even exposure to certain carcinogens,” he mused.
Ultimately, Cannon hopes this initial study encourages runners to consider undergoing screening colonoscopies before hitting 45. “I do believe it should raise awareness that any bleeding for a runner is a reason to get a colonoscopy, and not something to be ignored,” he remarked. “Exercise is beneficial overall—don’t let this serve as an excuse to avoid it.”
