New research from the University of Copenhagen suggests that habitual coffee consumption may influence the digestive system in ways that go beyond a morning jolt. The study, published in the journal Gut Microbiology, found that regular coffee drinkers show differences in gut motility, acidity, and microbial diversity compared with those who drink coffee less often.
Tracking digestion from the inside
To observe what happens inside the digestive tract, the Danish team used a small electronic capsule that participants swallowed. The device measured transit time, temperature, pH levels, and intestinal contractions as it moved through the gastrointestinal system.
The study involved 61 healthy adults in Denmark, divided into two groups based on their coffee habits. One group drank between one and five cups daily on more than three of the eight study days; the other group consumed coffee less frequently.
Results showed that regular coffee drinkers had a greater diversity of gut microorganisms compared with infrequent consumers. This aligns with earlier research suggesting coffee can shape the composition of the microbiome, the community of bacteria and other microbes living in the intestines.
Lead researcher Francesca Bucci, a PhD student in the Department of Nutrition, Exercise and Sports at the University of Copenhagen, said that regular coffee consumption appears to affect intestinal physiology. One notable finding was that regular drinkers had significantly lower acidity levels in the small intestine.
The team also observed a link between higher coffee intake and more frequent contractions in the colon, the muscular movements that help push waste through the digestive system. These contractions support digestion and regular bowel movements, potentially reducing constipation and maintaining muscle tone.
Bucci noted that intestinal contractions can aid proper digestion and help keep the intestinal muscles in good shape. However, the researchers are not yet sure whether the lower acidity in the small intestine is beneficial or potentially harmful.
Correlation, not causation
The authors stress that the study cannot prove coffee directly causes these changes. But Henrik Munch Roager, associate professor and head of the research group, said there are reasons to believe coffee plays a role. Previous studies have shown that coffee affects several digestive processes, including stomach acid secretion.
“That evidence makes it likely that the differences we observed are linked to coffee rather than coincidence,” Roager said. He added that many people notice from their own experience that coffee affects their digestion.
The next step, the team says, is a controlled trial in which participants’ coffee intake is regulated, rather than simply observing their habits. Such a design would help clarify whether coffee is indeed the driving factor.
This research adds to a growing body of work on how diet shapes the gut microbiome, a topic with implications for metabolic health and beyond. While the findings are preliminary, they offer a plausible mechanism for why many Europeans report that coffee helps keep them regular.
