Good coffee—even decaf, according to one baffling study—can really send you racing to the bathroom. Listeners to Marc Maron’s WTF podcast were long forced to think about this bowel-shaking phenomenon over years of the comedian’s scatological ad reads, but modern medical science has yet to really land on a settled explanation for why coffee makes so many people need to drop a deuce. One 2025 medical paper described it, I think hyperbolically, as “the subject of ongoing debate worldwide.”
Microbiologists and nutrition researchers at the University of Copenhagen have now taken this question directly to the source, asking 50 Danish adults to swallow a wireless research capsule, called the “SmartPill,” to investigate what coffee is doing inside their bowels. The team’s tiny gastrointestinal explorers found that regular coffee drinkers typically experienced “increased contractions in the colon,” as the new study, published in Gut Microbiology, put it. This added agitation, they theorize, might just be what makes coffee drinkers so ready to poop.
Something else also happened to the more serious coffee achievers: They displayed higher acidity in their small intestine and pH levels lower than more infrequent coffee drinkers.
“But perhaps more importantly, frequent coffee consumption appears to affect the physiology of the gut itself, in other words how the gut functions,”
