Study links regular coffee drinking to changes in gut motility and microbiome

Researchers at the University of Copenhagen in Denmark have found that drinking coffee regularly may be linked to changes in how the digestive system works, including bowel movement and colon contractions, as well as to greater diversity of gut bacteria. The study appeared in the journal "Gut Microbiology", which specialises in research on gut microorganisms. It set out to examine how habitual coffee consumption relates to physiological conditions inside the digestive tract.

How the study worked

Participants swallowed a small electronic capsule that recorded several measures as it travelled through the digestive tract: the time contents took to pass through, temperature, acidity and intestinal contractions. The study involved 61 healthy adults in Denmark, split into two groups. The first group drank between one and five cups of coffee a day on more than three of the eight days covered by the study; the second drank coffee less often.

Main findings

People who drank coffee regularly had a more diverse community of microorganisms in their intestines than those who drank less. They also had much lower acidity in the small intestine. The team also noted a link between higher coffee intake and more frequent contractions in the colon, which are muscle movements that help push intestinal contents onward.

Francesca Bucci, the study's lead researcher and a PhD student in the university's Department of Nutrition, Exercise and Sports, said such contractions can support proper digestion, help reduce constipation and help maintain the functional state of the intestinal muscles. The researchers cannot yet say whether lower acidity in the small intestine is beneficial or harmful.

Is coffee responsible?

The authors emphasise that the study cannot prove coffee directly causes the observed changes. Henrik Munch Roager, associate professor and head of the research group in the same department, nevertheless sees reasons to think coffee plays a role. Earlier studies have shown that coffee affects several digestive processes, including the secretion of acid in the stomach, which in his view makes it likely the differences are linked to coffee rather than coincidence.

The next step, the team says, would be a study that controls how much coffee participants drink instead of only observing their habits. That would help establish whether coffee actually causes these changes and clarify the mechanisms behind its effects on bowel movements and contractions.