If your morning coffee sometimes sends you straight to the bathroom, you're not alone. Coffee's reputation for getting things moving is well known, but scientists are still figuring out exactly how it affects digestion.
A new study from the University of Copenhagen suggests that regular coffee drinking is linked to differences in both gut bacteria and intestinal activity. Published in Gut Microbiology, the findings offer new clues about coffee's effects on digestion, although they don't establish that it improves gut health or relieves constipation.
Researchers followed 61 healthy adults in Denmark over nine days, recording what they ate and drank. Fifty participants also swallowed a small electronic capsule that tracked conditions inside their digestive systems, including how quickly things moved through the gut and how actively their intestines were working.
People who drank coffee regularly had a greater variety of gut bacteria on one measure than those who rarely drank it. While previous research has also linked coffee to changes in gut bacteria, greater variety doesn't necessarily mean better gut health.
The researchers also found differences in intestinal activity. People with higher levels of certain substances produced as the body breaks down caffeine tended to have more contractions in their colons. These contractions help move waste through the digestive system.
But there's a catch: More contractions didn't necessarily mean things moved faster. The researchers found no significant difference in how long it took material to pass through the colon between frequent and infrequent coffee drinkers.
Frequent coffee drinkers also had slightly more acidic conditions in their small intestines. That may influence how food is digested, but researchers don't yet know whether the difference has any meaningful effect on health.
The findings don't establish that coffee causes these changes. Participants weren't assigned specific amounts of coffee, and researchers didn't control how it was prepared. The study also involved a relatively small group of healthy adults, so the results may not apply to everyone.
Still, the research adds to our understanding of coffee's relationship with digestion. Scientists hope that future studies comparing periods of regular coffee drinking with periods without coffee will help determine whether the differences they observed could eventually lead to better ways of managing constipation and other digestive concerns.
This research was supported by the Novo Nordisk Foundation and the European Union's Marie Skłodowska-Curie Actions program.