Research Study Uncovers Unusual Connection Between Marathon Running and Cancer
Some of the fittest people in the world may be at risk. A new research study reveals a possible link between running marathons and colorectal cancer.
The study was conducted by oncologists at the Inova Schar Cancer Institute in Virginia, examining the colon of relatively young individuals who had run several long-distance races. They found that these runners had a much higher rate of potentially dangerous adenomas (a type of polyp) than expected for someone their age. Although these are preliminary findings and confirmation is required, they could point to a real connection between colorectal cancer and extreme physical activity.
A mysterious trend
Timothy Cannon, the lead researcher, was inspired for this study after treating three young patients with colorectal cancer. The three had run ultra-marathons (races longer than 26.2 miles). Not only were they physically fit, but they were much younger than typical patients, with the oldest being 40 years old.
In 2022, Cannon and his colleagues began recruiting endurance athletes for their future study. The volunteers had run at least two ultra-marathons or five traditional marathons, had no family history of colorectal cancer or other apparent risk factors. One hundred athletes between 35 and 50 years old took part in the study and underwent colonoscopies.
The researchers then looked for advanced adenomas in the colon of each volunteer. These are relatively large and unusual-looking polyps, and although they are benign polyps, they have a higher risk of becoming cancerous compared to other polyps. They then compared the rate of finding these polyps in athletes with historical trends.
It is expected that around 1.2% of people around 40 years old with an average risk of colorectal cancer have advanced adenomas, according to the researchers. The large contrast in this study was that 15% of the evaluated runners had them, while almost half had polyps in general.
“Refined assessment strategies should be considered for this population,” the researchers wrote in their work.
Much remains to be understood
The team presented their results this year at the annual conference of the American Society of Clinical Oncology. This means that the study has not yet undergone the formal peer review process. The authors also point out that their work does not constitute definitive proof that endurance races can cause colorectal cancer.
But assuming there is a causal link, the question of why remains unanswered. Every weekend, 5,000 people run, and most of them know that occasionally after a run, one may experience gastrointestinal discomfort. These injuries sometimes stem from temporarily restricted blood flow to the intestines, damaging nearby cells. It is possible, speculate the researchers, that extreme runners who regularly undergo this restricted blood flow process may develop the type of chronic inflammation that increases the likelihood of cancer.
However, at this time, this is just a hypothesis of what might be happening. The researchers say that in future studies, efforts should be made to confirm these findings and discern the causes and risk factors that could explain the potential elevated risk.
The study should not discourage those who run or exercise. The many benefits of regular physical activity for health include a lower risk of at least eight different types of cancer, outweighing the risks for the average person.
