© Christopher Welsch
November 13, 2026
Marianne Waldenfels
Can coffee really help relieve constipation? Researchers in Copenhagen used a swallowable capsule to investigate what happens in the digestive tract of regular coffee drinkers. Their findings reveal a link between coffee and bowel activity – and suggest that caffeine is only part of the story.
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Coffee doesn't just wake you up. In some people, it gets digestion moving within just a few minutes. The fact that coffee affects gut activity has been known for decades. Researchers at the University of Copenhagen have now taken a closer look at exactly what happens in the digestive tract, using a swallowable measuring capsule. Their findings reveal how closely coffee consumption and gut motility are linked — and offer new clues as to whether coffee might also help with constipation.
For their study in the journal Gut Microbiology researchers at the University of Copenhagen studied 61 healthy adults who kept records of their diet and coffee consumption over eight days. Fifty of them swallowed an electronic capsule that measured acidity levels, transit time, and muscle activity in the gut as it passed through the digestive tract.
The most striking finding: the more coffee the participants drank, the more frequently the capsule detected muscle contractions in the large intestine. These contractions help mix and propel the intestinal contents along. Whether stool actually passes through more quickly as a result, however, remains unclear.
The scientists also found a more acidic environment in the small intestine and greater diversity of gut bacteria in regular coffee drinkers. The health implications of the altered acidity level are not yet clear.
For lead author Francesca Bucci, the increase in gut contractions is of particular interest: they could help prevent constipation. Whether coffee actually has this effect, however, still needs to be investigated in clinical studies.
As far back as 1990, British researchers led by S. R. Brown surveyed nearly a hundred healthy individuals about their experiences. Twenty-nine percent reported feeling the urge to use the toilet after drinking coffee, with women reporting this more often than men.
In the same study in the journal Gut the researchers used a pressure probe to measure muscle activity in the final section of the large intestine. In participants who were already familiar with this effect from personal experience, activity increased as early as four minutes after drinking coffee and remained elevated for at least half an hour. No such response was observed in the other participants, and hot water had no comparable effect.
Four minutes is far too short a time for the coffee to have already reached the large intestine. The researchers therefore suspected that a reflex is at work: signals from the stomach and upper digestive tract trigger the intestinal muscles to contract further down. The digestive hormone gastrin may also play a role.
The fact that this effect often occurs in the morning fits with the natural rhythms of digestion. Activity in the large intestine increases anyway after waking and after a meal — coffee appears to amplify this process further.
Not entirely. The 1990 study already showed that decaffeinated coffee can also stimulate the gut. A further study from 1998 confirmed this in twelve healthy adults. Regular coffee produced stronger gut contractions than decaffeinated coffee, but the decaffeinated version still had an effect.
Caffeine appears to amplify the response but is not solely responsible for it. Which other components of coffee are involved has not yet been fully established. People who do not tolerate caffeine well can therefore try whether decaffeinated coffee also stimulates their digestion.
No precise amount can be derived from existing research. That said, larger population studies suggest that moderate coffee consumption may be associated with a lower risk of constipation.
An analysis of 7,844 adults from 2024 found that people who drank one to two cups of caffeinated coffee per day experienced constipation less frequently. No corresponding association was found for decaffeinated coffee.
A further analysis of nearly 13,000 adults from 2025 reached a similar conclusion: moderate caffeine intake was associated with less chronic constipation, though at very high intake levels this association reversed.
Why this is the case remains unclear. The commonly cited explanation that coffee draws water from the body and thereby hardens the stool is not convincing. With regular, moderate consumption, coffee does not typically lead to any meaningful fluid loss.
Both studies also show only statistical associations. They cannot establish whether coffee itself reduces the risk of constipation.
The new Copenhagen study does not yet provide proof of this either. It examined only 61 healthy adults, not people with chronic constipation. Furthermore, participants drank coffee according to their own usual habits. Whether the observed differences are actually attributable to coffee would need to be confirmed by a controlled study.
Coffee can stimulate gut motility within just a few minutes. Whether it also helps with chronic constipation, however, has not been proven. People who regularly suffer from symptoms should therefore not rely on extra cups of coffee. More important are a fiber-rich diet, adequate fluid intake, and regular exercise. If symptoms persist or bowel habits change suddenly, the underlying causes should be investigated by a doctor.
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