Study Finds 15% of 94 Extreme Runners Had Advanced Colon Polyps
Updated
Updated · The Washington Post · May 21
Study Finds 15% of 94 Extreme Runners Had Advanced Colon Polyps
2 articles · Updated · The Washington Post · May 21
Nearly half of 94 runners aged 35 to 50 who had completed at least five marathons or two ultramarathons were found to have colon polyps, and 15% had advanced adenomas during colonoscopy screening.
Timothy Cannon launched the study after treating three prolific runners under 40 with advanced colon cancer; he says repeated gut blood-flow loss, inflammation and tissue repair during extreme endurance exercise could help explain the findings.
The advanced-polyp rate was far above the roughly 1.2% to 6% historically seen in screening colonoscopies for adults in their late 40s, but the study found no colon cancer and had no non-runner control group.
Gastroenterologists called the results preliminary and hypothesis-generating, stressing that moderate exercise is still broadly protective against colorectal cancer and that runners should not stop running.
Researchers are planning a larger study of about 300 extreme runners plus a similar-sized control group; for now, they urge endurance athletes with persistent bloating, cramping or rectal bleeding to seek medical evaluation.
Is it the mileage or the high-sugar fuel that's raising colon cancer risk for endurance athletes?
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High Rates of Colon Polyps and Advanced Adenomas Found in Extreme Endurance Runners: New Study Raises Questions About Colon Health Risks
Overview
A recent study led by Dr. Timothy Cannon at the Inova Schar Cancer Institute, presented at the 2025 ASCO conference, investigated colon health in 100 marathon and ultramarathon runners aged 35 to 50. The research found that nearly half of these extreme endurance athletes had colon polyps, and 15% had advanced adenomas—rates much higher than typically seen in the general population. These surprising findings highlight a potential link between intense endurance exercise and colon abnormalities, prompting further research to understand the risks while emphasizing that exercise remains broadly beneficial for health.