Possible colon cancer risk linked to marathon runners

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A new study published in the Journal of Clinical Oncology suggests that marathon runners may face an unexpected increase in colon cancer risk, highlighting that extreme endurance exercise is not universally protective. Researchers suggest that prolonged physiological stress, repeated dehydration, and reduced blood flow to the gut during intense long-distance running could contribute to cellular changes in the colon over time. While the overall health benefits of regular exercise remain strong, the findings suggest that high-endurance athletes may benefit from closer attention to gastrointestinal symptoms and routine screening.

Source

Cannon TL, Bonomelli S, Swain WR, et al. Risk of pre-cancerous advanced adenomas of the colon in long distance runners. J Clin Oncol. 2025;43(16 suppl). doi:10.1200/JCO.2025.43.16_suppl.3619

Additional Reading

https://www.health.com/is-marathon-running-linked-to-colon-cancer-11798631

https://www.sciencefocus.com/news/ultra-running-colon-cancer

https://www.nytimes.com/2025/08/19/health/running-colon-cancer.html