Long distance running like marathons and ultra marathons aren’t necessarily the health badge we thought of. In fact, it could increase you Cancer riskaccording to a new study from Virginia.
Dr. Timothy Cannon of the INOVA Schar Cancer Institute has launched a study presented at the 2025 American Society of Clinical Oncology (ASCO) Annual Meeting in Chicago after realising that Ultramarathoners under the age of 40 had appeared in advanced colon cancer.
To dig deeper, he began studying runners who completed at least five marathons or two ultra marathons, except for family history and other known risk factors.
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“This study supports the hypothesis that extreme endurance runners increase the risk of precancerous polyps,” Cannon told Fox News Digital.
The researchers looked at 100 participants between the ages of 35 and 50 who had never had colonoscopy but completed at least five marathons or two ultra marathons. Those with hereditary cancer syndrome or inflammatory bowel disease were excluded to focus on the potential effects of endurance exercise alone.
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Each participant underwent colonoscopy during the study. They also completed research on dietary habits, intestinal history and long distances Execution pattern.
He found that 15% suffer from advanced adenomas or pre-cancer colon growth, compared to the usual 1-2% of the age group. Furthermore, a staggering 41% had at least one adenoma.
Growth discovered during the procedure was reviewed by a panel of gastroenterologists, pathologists and oncologists to determine whether they met the criteria. Advanced adenoma.
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“I was surprised how many of the runners had polyps,” Cannon said.
“I thought they might have more adenomas and advanced adenomas than would be expected for that age group…but I never imagined 15% had advanced adenomas.”
The average age of participants was 42.5 years, with a typical screening age of 45 years.
Cannon and other experts theorize that intense endurance training can cause repeated “gut stress.” During long running, blood detours away from the intestines, possibly causing damage and inflammation. Over time, it can lead to mutations and polyps.
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Experts warn that the results are inconclusive, and note that the study lacks a control group and has not yet undergone peer review. Still, numbers may make you sit and pay attention.
“We didn’t have a control group, so this raises questions about whether there were some biases,” he added that the runners are primarily from the Washington, DC area and may have other common risk factors other than running.
He also acknowledged that the study did not explain detailed family history, which may have influenced the outcome.
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Despite the outcome, it is not a sign of a completely running groove.
“Let’s first say people should. Continue exercising, The cannon emphasized. “There are far more issues with not exercising too much than exercising too much.”
He added that exercise reduces the risk of cancer, despite the study supporting the idea that extreme doses such as ultramarathons can increase the risk of cancer.
For people who run extreme distances, it is important to monitor symptoms such as bleeding, persistent diarrhea and abdominal pain.
Bleeding after a run should not be considered normal or benign, and anyone experiencing it should seek medical attention.
“As far as I know, the gastroenterologist experts said rectal bleeding and blood in the stool were not the cause of concern,” Cannon said.
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“But my patients actually say that many gastroenterologists dismiss the bleeding after running as a regular event.”
