Study links coffee consumption to increased colon activity and gut bacterial diversity
Researchers using ingestible sensors found that frequent coffee drinkers show stronger colon contractions, lower small-intestine pH and greater bacterial richness, offering a possible explanation for the common urge to defecate after coffee.
Scientists at the University of Copenhagen have investigated why coffee often triggers a bowel movement. In a 2025 study published in Gut Microbiology, 50 Danish adults swallowed a wireless capsule that recorded temperature, pH, pressure and transit time throughout the gastrointestinal tract. The data showed that participants who drank coffee regularly (one to five cups on at least three of eight study days) experienced more frequent colon contractions and lower pH levels in the small intestine compared with less frequent drinkers.
The researchers also analyzed stool samples and observed higher bacterial biodiversity among the frequent coffee consumers, although the overall bacterial load was similar between groups. The study’s first author, Francesca Bucci, a PhD student in nutrition, said the findings suggest that coffee may alter gut physiology, increasing the mixing of food and microbes in the colon.
Coauthor Henrik Munch Roager, head of nutrition, microbiome and metabolomics research at the university, noted that many people suffer from constipation and irregular bowel movements, and that understanding coffee’s impact on intestinal motility could eventually inform natural treatments for such conditions. The team emphasized that further research is needed to determine how colon contractions, pH changes and bacterial diversity each contribute to the “coffee-poop effect.”