A symbol of endurance and vitality, the marathon could however have a little-known downside. Researchers at the Inova Schar Cancer Institute, located in Virginia (United States), observed in a study that long-distance runners have precancerous polyps more often than the general population of the same age. Long considered a protection against chronic diseases, intensive endurance running raises questions when it exceeds the body’s physiological limits.
According to the online media Gizmodo, the group of scientists relied on the analysis of the colons of 100 athletes aged 35 to 50 years old. All of them are used to running marathons or ultramarathons and none of them have a family history of colorectal cancer. The results are striking: while only 1.2% of middle-risk forty-year-olds normally have advanced tumors, this figure rises to 15% among these endurance athletes.
Half of the participants had benign polyps, but still likely to evolve. This proportion, which is well above historical trends, has sparked strong reactions from scientists. “We did not expect such tumor rates at high risk, which are precancerous lesions, in an age group like this”recognized David Lieberman, gastroenterologist at Oregon Health and Science University, interviewed by the daily The New York Times.
No certainties yet
Timothy Cannon, a researcher at the Inova Schar Cancer Institute, was himself alerted after following three ultramarathon patients with colorectal cancer, the oldest of whom was only 40 years old. Figures which raise questions, especially since systematic screening is generally only recommended from the age of 50.
Scientists suggest that the extreme demands of endurance – particularly reduced blood flow to the intestines – could promote chronic inflammation, creating a breeding ground for cancer. But they remain cautious, their work, presented in June in Chicago at the annual conference of the American Society of Clinical Oncology, having not yet been validated by the scientific review of their peers.
Pending confirmation, specialists recommend increased medical monitoring for intensive runners, without calling into question the proven benefits of regular physical activity, associated with a reduction in the risk of at least eight different cancers. This study, however, invites us to question the border between beneficial sport and excess endurance. In health, researchers remind us, performance should never take precedence over balance.
