Exercise is a cornerstone of good health and evidence shows it can even help prevent cancers returning following treatment. But new findings are raising an unexpected question: could very high-volume endurance training carry its own risks?
At the 2025 American Society of Clinical Oncology meeting, researchers from Inova Schar Cancer Institute reported that a surprising number of dedicated marathon and ultramarathon runners had precancerous growths in their colons. Among 100 athletes aged 35 to 50, 15% had advanced adenomas – lesions that can develop into bowel cancer – while 41% had at least one adenoma.
