[proee]

Wow, I had no idea there is a 15X increase for endurance athletes. Make me want to dial down the running a bit, which make you wonder where the sweet spot is for distance training.

[ZeeSee]

It's rare but can happen where long distance running causes ischemic colitis which is where on a long run enough blood is diverted from the large intestine that it damages the intestine long term. It isn't surprising to me that there's higher likelihood of colon cancer given this. It seems like repeated bouts of lower blood for the intestine on long runs has a cumulative impact and damages the colon even if it doesn't cause ischemic colitis.

[sigmoid10]

This theory has been put forward, but it's important to point out that there is no real evidence yet. An alternative theory is diet, which is also the leading theory for increasing incidences in non-athletes. Highly processed, calorie dense foods have been on the watchlist for a while, and ultra endurance athletes have a special need for these to satisfy their caloric requirements. It could also be a combination of these factors or something else that was missed entirely so far.

[AstroBen]

I wonder if it's due to diet. Endurance athletes love their simple carbs, highly processed gels. I've seen plenty of cyclists taking gummy bears on rides for fuel, or a concoction that is effectively sugar water to drink

The study referenced is really light on details and they don't say if they controlled for that

[xaldir]

I was thinking the same thing.

Simple sugars and highly processed foods tends to affect the gut microbiome.

I guess "more ressearch is needed".

[PenguinCoder]

Interesting, I wasn't aware of that connection either. I was diagnosed with stage IV colon cancer, but was identified as 'genetic' and not caused by diet or lifestyle. I used to be a heavy runner too, done a few marathons, and plenty more 10k, 8ks etc. Wonder if that could be a correlation... Treatments have it contained/in maintenance so at least I have that going for me.

[greedo]

I too was diagnosed with stage 2 rectal cancer, but it was back in 2005. How did they determine your cause was genetic?

[javiramos]

Best of luck with your treatment.

[francisofascii]

I have an ultra-runner friend who just got diagnosed with stage 4 colon cancer. Absolutely devastating. He had a colonoscopy just a few years ago. His only symptom was not feeling well after a long race.

[parl_match]

It may be the damage of repetitive motion, it may be chemicals released into the bloodstream from endurance athletics. It may be something else. Without knowing the root cause, it's impossible to figure out the "sweet spot"

[elric]

Could be a lot of things. Lots of long distance runners consume a lot of sugary gels to keep going. Not sure what the typical composition is, but likely lots of glucose and no fibre.

The marathon runners I know also seem to eat tons of junk food, they can get away with it from a weight perspective because a long run will burn it off, but it could have other consequences.

Point being: there's a lot about long distance runners that's quite different from other people.

[tekno45]

i saw something recently that pointed to the fact that ultra runners end up with less blood in their guts while running for SO long its leading to cancers and such.

[reducesuffering]

It's not simply endurance athletes though. It was 2x ultra-marathons >26 miles, or at least 5 marathons completed.

[owenversteeg]

>2x ultra-marathons >26 miles, or at least 5 marathons completed

Yes, and it seems like it's really a 7.5x risk increase. Still pretty spectacular, though!

I really wonder what could cause that. Randomly throwing out possible causes: 1) blood redirected away from gut, 2) overuse of NSAIDS, 3) ultraprocessed foods (gels etc), 4) strange microbiome issues (gels + stress in gut from extreme exertion = altered gut flora?)

The study that found the result is DOI: 10.1200/JCO.2025.43.16_suppl.3619

[inglor_cz]

Which is way more than what original hunters and gatherers ever clock. They do move a lot, but not so much, and they alternate their activities a lot too (running, walking, resting, taking entire days off and just guarding their village).

We're not really optimized for this sort of extreme endurance and long-term development of serious pathologies is unsuprising.