I started running about a year ago. By running, I mean joining the cult known as parkrun on a Saturday morning. I am yet to run anything over 5k, and somewhere around the third kilometre, when I feel like I might die, I ask myself why I'm doing this. The answer is straightforward, as well as improving my endurance, running just 10 minutes a day is associated with a reduced risk of cardiovascular disease, dementia, and all cause mortality.
With all of these benefits in mind, I was surprised to discover that ultramarathon runners may in fact be at an increased risk of bowel cancer.
A recent observational study looked at advanced adenomas, which are precancerous polyps, in long distance runners aged 35 to 50. Colonoscopies were done for 100 participants who had completed at least two ultramarathons or five registered marathons. Of these, 15% were found to have advanced adenomas, compared to just 1.2% of the general population in the same age group. The proposed mechanism is reduced blood flow to the bowel during prolonged running.
Despite this, running still has a multitude of health benefits, but it may suggest that these long distance runners should undergo earlier bowel cancer screening and be aware of the potential symptoms of bowel cancer. More research needs to be done in this area.
In other news, I had my first ever colonoscopy this week. Exciting times. There was lots of pooping.
👋 For the new joiners: I’m Suraj, also known as Dr Sooj - a primary care doctor & health content creator. I love navigating the complex world of health and wellness and breaking down complicated concepts.
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Suraj (Doctor Sooj)
References:
Cannon TL, Bonomelli S, Swain WR, Kaltman RD, Mani H, Xia M, Randall J, Al-Kawas FH, et al. Risk of pre-cancerous advanced adenomas of the colon in long distance runners. J Clin Oncol. https://ascopubs.org/doi/10.1200/JCO.2025.43.16_suppl.3619