Marathon running and precancerous colon growths

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A small preliminary study published in the Journal of Clinical Oncology found that marathon and extreme runners showed higher rates of precancerous colon growth than non-runners, though the reasons are unclear. Possible factors include gastrointestinal stress from long-distance training, inflammation, or simply chance due to the study’s limited size. Physical activity still offers well-established health benefits, but endurance athletes should keep up with routine colon cancer screening and pay attention to ongoing digestive symptoms.

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

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

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