We’re used to thinking of long-distance runners as the embodiment of health: lean warriors soaking head to toe in endorphins as they run 100-mile trails for fun, their heart rates so low they could be mistaken for corpses. A recent study, however, is flipping that narrative: the most intense runners among us might be more prone to colon cancer.
It all started when Dr. Timothy Cannon, an oncologist at Inova Schar Cancer Institute, noticed something off. Three of his patients, all under 40, were super-fit endurance athletes. They didn’t drink. They didn’t smoke. One was vegan. Yet all had advanced colon cancer, and none of the usual risk factors. So, he turned this mystery into a research study.
In the study, highlighted by The New York Times, Cannon recruited 100 distance runners aged 35 to 50 for colonoscopies, expecting to find very little. Instead, nearly half had polyps, and 15 percent had advanced adenomas, the kind that like to turn cancerous eventually.
Fifteen percent may not sound high, but it’s astronomical. It far exceeds the percentages of the general population — 4.5 to 6 percent — as well as Alaska natives, which sounds like a weird thing to toss in there, but it’s a group of people with one of the highest colon cancer rates in the United States, sitting at 12 percent.
Most of these runners were completely unaware, oblivious to the fact that cancer was building up inside of them. Many chalked up symptoms like bloody stools or cramps to “runner’s trots” or other benign side effects of extreme exercise.
One man, Josh Wadlington, ran multiple ultramarathons a month and ignored his symptoms for years. He died at 41. Two others who inspired the study are also gone.
Doctors are still sorting out whether endurance running causes the problem or just hides it. One theory suggests that intense exercise reroutes blood away from the gut, starving colon cells of oxygen and triggering a cycle of inflammation and repair that the body can only do so many times before it falls apart. How many times can you patch the same flat tire before the tire is no longer functional?
Still, experts say more research is needed, since the study lacked a control group. Muddying the waters even more is the fact that early-onset colon cancer is on the rise, with nearly 10 percent of new colorectal cancers around the world being diagnosed in people under the age of 50. This, again, raises the question of whether this is exclusive to extreme runners or is, unfortunately, par for the course now.
There isn’t enough information to determine whether you should throw out your running shoes and take up cycling instead. There is, however, enough to suggest that if you’re a dedicated marathon runner and something in your body feels off, don’t just chalk it up to normal runner’s wear and tear. It might be something a lot more serious.
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