Recent studies suggest that some of the most physically fit individuals may face an unexpected health risk: a possible connection between marathon running and colorectal cancer. Oncologists at the Inova Schar Cancer Institute in Virginia have conducted groundbreaking research, focusing on the colons of relatively young athletes who have participated in multiple long-distance races. Their findings reveal that these runners exhibit a significantly higher rate of potentially dangerous adenomas—polyps that can lead to cancer—compared to what is typically expected for their age group.
Though the results are preliminary and require further validation, they hint at a concerning association between colorectal cancer and extreme physical activity. "It tells us there’s a signal here," stated David Lieberman, a gastroenterologist and professor emeritus at Oregon Health and Science University, who was not involved in the study. "We wouldn’t have expected these rates of high-risk adenomas, which are cancer precursor lesions, in an age group like this." This statement underscores the need for further exploration into this unexpected trend.
Lead researcher Timothy Cannon was motivated to conduct this study after treating three young patients diagnosed with colorectal cancer, all of whom were ultramarathon runners. These patients were not only exceptionally fit but also significantly younger than the average colorectal cancer patient, with the oldest being just 40 years old. In 2022, Cannon and his team began recruiting endurance athletes for their prospective study, specifically targeting individuals who had completed at least two ultramarathons or five regular marathons without any family history of colorectal cancer or other risk factors.
A total of 100 athletes aged between 35 and 50 participated in the study, undergoing colonoscopies to investigate the presence of advanced adenomas—larger or unusual polyps that carry a higher risk of becoming cancerous. According to the researchers, about 1.2% of individuals in their 40s at average risk for colorectal cancer would typically be expected to have advanced adenomas. In stark contrast, 15% of the runners studied had these polyps, and nearly half had polyps in general. "Consideration of refined screening strategies for this population is warranted," the researchers wrote in their findings.
The research team presented their findings at the annual conference of the American Society of Clinical Oncology earlier this year, but it is important to note that this study has not yet undergone the formal peer-review process. The authors acknowledge that their work does not definitively prove that endurance running leads to colorectal cancer. However, if this potential link is confirmed, it raises crucial questions regarding the mechanisms involved.
One hypothesis suggests that the physical strain of long-distance running may cause temporary blood flow restrictions to the intestines, potentially leading to chronic inflammation and increasing the risk of cancer. As many runners can attest, gastrointestinal distress, often referred to as runner’s diarrhea, can occur during races. This distress may be an indication of underlying physiological responses that need to be further investigated. The researchers emphasize the importance of conducting future studies to confirm their findings and to explore the various causes and risk factors that could contribute to this alarming trend.
In summary, while the link between marathon running and colorectal cancer remains to be fully understood, this innovative research opens the door for more in-depth studies and refined screening protocols for athletes engaged in extreme physical activity.
