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.

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ZeeSee 3 hours ago | parent | next [-]

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 an hour ago \| parent [-]
		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.

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PenguinCoder an hour ago | parent | prev | next [-]

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 13 minutes ago \| parent [-]
		I too was diagnosed with stage 2 rectal cancer, but it was back in 2005. How did they determine your cause was genetic?

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parl_match 3 hours ago | parent | prev | next [-]

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 3 hours ago \| parent \| next [-]
		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.
	▲	3 hours ago \| parent \| prev \| next [-]
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	▲	tekno45 3 hours ago \| parent \| prev [-]
		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.

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reducesuffering 3 hours ago | parent | prev [-]

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

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owenversteeg an hour ago | parent | next [-]

>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

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inglor_cz 2 hours ago | parent | prev [-]

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.

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greygoo222 2 hours ago | parent [-]

You shouldn't so offhandedly assume a hunter-gatherer lifestyle couldn't lead to issues like increased risk of CRC, or that activities which lead to increased risk of CRC couldn't be what hunter-gatherers did. Evolution is neither fast nor perfectly precise. Plenty of animal populations have common health problems that simply weren't harmful enough to reproduction to be selected out, much less something rare and late-onset like CRC.

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inglor_cz 2 hours ago | parent [-]

I don't assume anything. From what we know about health of the last surviving hunter-gatherers, they suffer significantly less from "diseases of civilization" when taken in proportion to their settled neighbours. Some of those diseases (such as high blood pressure or diabetes 2nd type) seem to be totally absent in them. Cancers do happen, but not as often.

This pattern is quite old. Already ancient Egyptians suffered from civilizational diseases much more than hunter-gatherers, especially the richer ones (heart attacks, gout, cancer).

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greygoo222 an hour ago | parent [-]

I won't bother checking or disputing the accuracy of your factual claims, because it does not matter.

Colorectal cancer is not the same thing as high blood pressure, or type 2 diabetes, or any other cancer that isn't colorectal cancer. Diseases are not a monolith and you cannot assume low risk of some diseases means low risk of others. That is wild guesswork passed off as logic, like measuring the shadow your testicles cast on the wall and announcing it is 24.1 degrees Celsius. Ultra-marathon runners also have low risk of type 2 diabetes!

Do you have specific evidence that modern hunter-gatherers have low rates of colorectal cancer that cannot be explained by survivorship bias, screening, genetic differences, and all other confounders, and that they are representative of historical hunter-gatherers? No? Then you cannot confidently conclude that hunter-gatherers didn't experience elevated rates of CRC.

	▲	pfannkuchen an hour ago \| parent \| next [-]
		Absolutely, we may have a depressed rate of CRC where ultramarathoners just get back up to the historical baseline. Who knows, but we don’t know it isn’t that.
	▲	inglor_cz an hour ago \| parent \| prev [-]
		"Diseases are not a monolith and you cannot assume low risk of some diseases means low risk of others. That is wild guesswork passed off as logic..." Diseases are not a monolith, but they do tend to arise and fall in some specific clusters, and that is not "logic", good or bad (too many computer-minded people drag logic into the chaos that is biology), but rather a long-time empirical observation, albeit with some exceptions.