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You Drank Some Coffee and Now You Have to Poop. But Why?

The latest episode of Reactions, a series from the American Chemical Society, addresses the age-old question: Why does coffee make you poop?


We’ve tackled this question here on io9 before. As we noted then, the short answer is that coffee stimulates muscle contractions along the terminal portion of your large intestine, a stretch of guts called the rectosigmoid colon. What’s less clear is how coffee stimulates these contractions. In this video, the ACS gets into some of the chemistry that is hypothesized to trigger these effects, specifically coffee’s ability to promote the release of Gastrin and Cholecystokinin, both of which have been shown to increase activity in the colon. For more details on these and other coffee ingredients that may regulate pooping, check out our explainer on the topic, which also covers one of the earliest studies to investigate the link between coffee and colon contractions (it even involves anal probes!).


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I don’t drink coffee all that often, but last week in a conference meeting someone brought in Starbucks. I had slept like hell the night before so I got a fairly large cup and some donuts.

Twenty minutes into the meeting I heard a sound that could be best described as a slow trombone slide note. It felt as if my stomach had completely turned upside down. Then it relaxed.

Ten minutes later I found the sharp pain that had me clenching as if I was trying to hold a grain of sand between my buttcheeks. As oon as I felt like I could, I made a total bee line toward the bathroom like Conan up there.

I made it. All was safe, though the hallway was eerily empty for another 30 minutes.

Seriously though. Fuck coffee.