Regular Coffee Drinking Appears to Change How the Gut Works

Drinking coffee regularly may affect more than the bacteria in your digestive system. A University of Copenhagen study suggests it may also change how the gut itself functions, a finding that could eventually inform better treatments for constipation.

The research team had a group of Danish participants swallow a small electronic capsule. While moving through the digestive tract, the capsule recorded transit time, temperature, pH levels, and intestinal contractions, among other measures. Participants were sorted into two groups: frequent coffee drinkers, who had one to five cups a day on more than three of the eight study days, and people who drank coffee less often.

As earlier studies had suggested, the results confirmed that coffee influences the makeup of gut bacteria. Frequent drinkers had a more diverse set of microorganisms than those who drank less.

“But perhaps more importantly, frequent coffee consumption appears to affect the physiology of the gut itself, in other words how the gut functions,” said Francesca Bucci, first author of the study published in ScienceDirect.

Moderate coffee intake is already linked to a lower risk of cardiovascular disease, diabetes, depression, and several types of cancer. Far less is known, however, about how habitual coffee drinking relates to conditions inside the gut.

The team found that frequent drinkers had a significantly lower pH in the small intestine, and that higher coffee intake went along with more contractions in the colon. “Contractions in the gut can support healthy digestion, help prevent constipation and keep the intestinal muscles in good condition,” added Bucci.

Whether the lower pH is good or bad for health is not yet clear. Still, pH in the small intestine plays an important role in how active digestive enzymes are and how food is broken down.

The authors also point out that the study cannot show that coffee alone produced these differences. Senior author Henrik Munch Roager nonetheless sees good reason to think coffee is a key factor.

“For example, we already know from other studies that coffee can influence a range of processes in the digestive system, including acid secretion in the stomach. So, there are good reasons to believe that what we are seeing is not merely coincidence. Anecdotally, many people also report that coffee affects their digestion,” Munch added.

Roager says the logical next step is an intervention study. In it, investigators would control how much coffee participants drink and compare gut physiology during periods of high coffee intake with periods of none.

The team hopes this and later work can help with a common problem.

“A great many people struggle with constipation and irregular bowel movements. If we can understand how coffee affects digestion and intestinal contractions, it may be possible to use that knowledge to stimulate gut motility in a natural way. That would be extremely valuable,” Roager said.