Can running be bad for you?

I remember seeing the articles start to circulate last year. It was in the middle of race season, and I was following some of my favorite road runners’ transitions to the trails and ultra distances. The correlation was between extreme distances and the incidence of colorectal cancer. Without reading closely, it had a logic: distance running is hard on your gut, creating an inflamed environment that gives rise to pre-cancerous lesions.

Today, I read those same articles with a more nuanced view. We know why distance running is hard on your gut, so what can we learn from that environment to help reduce the risk of developing colorectal cancer? I’m not suggesting running lower volume, because if endurance is your drug, the risk likely seems worth it. But I do suggest we might gain insight by following marathoners and ultramarathoners to learn about diet, training load, microbiome, and gut stress. Can we learn how the environment and diet impact both runners and the general population?

Then I got my own colorectal cancer diagnosis. The intellectual question I’d been turning over for a stranger’s body suddenly belonged to me. And now it had a different shape. Not “is there a link?” but “given what I know about my gut, my surgery, and my surveillance ahead, how much do I want to lean on running the way I used to?” What I’d been reading as a curious observer, I now read as a participant. And the answer, it turns out, isn’t about whether running caused this. It’s about whether the version of running I was building toward — longer, harder, more — still fits the body I’m now in, the recurrence risk I’m managing, and what I actually want from my running.

Basebuilding 2.0

My bruises from surgery are starting to fade, my incisions are less sensitive with each passing day, and my experiments with diet are showing early signs that my gut adaptation is on track, if not ahead of schedule. All of this has me thinking about what a return to running will look like once my surgeon gives me the green light.

But where in 2024, my sights were definitely set on at least a half, if not a full, as a measure of success, now I’m reconsidering what volume and distance I want to establish as my base for the future.

Some of that is pragmatic. With a shortened colon that handles digestion differently, I’ll likely face practical constraints — how long I can run, what hydration looks like, and what fueling strategies make sense if I do stretch beyond a 10k — and, underneath all that, how much GI stress I want to invite back into a system I’d rather not give a reason to misbehave.

The why of my running

As I get older, and my increasingly complex health reshapes what I value, some of it is more philosophical. I will always be a runner, but if you look at the front of my fridge (yes, that’s where I hang my bibs), you’ll see everything from a 2k (thanks, stress fracture in my foot) to full marathons, with a few ultras sprinkled in. The 10k and half have always been my sweet spot. But increasingly, 5-10k is feeling more like my comfort zone.

And that’s an interesting shift. If you asked me why I run, my most common answer would be to push my body, and then, to get out of my head and feel connected to my surroundings. What’s creeping into my consciousness is that over the last two years, those priorities have flipped. Lacing up my shoes is about meeting my body where it’s at, exploring what it can do on any given day, and, always, about a reset from my otherwise busy days that often find me living in my head. I like the physical nature of movement, but I get the most from the mental reset.

Shifting towards joy

So that’s where I’m landing. Not retiring from distance — I’ll never close that door — but giving myself permission to let 5-10k be the goal rather than the warm-up. To run because my body wants to move, not because a training plan says I owe it 14 miles on Sunday. The marathoners and ultrarunners can keep teaching us about the gut. I’ll be over here, running my 5k, learning from a gut that’s already taught me more than I wanted to know.

There’s a version of this story where a cancer diagnosis takes something away from me, and I’m not interested in writing it.

The bibs on the fridge aren’t going anywhere. But the next ones might be earned by showing up for the run I actually want to do that morning, on a gut that’s still figuring out its new normal, in a body I’m learning to listen to differently.

Joy, it turns out, is a pretty good training metric.