A simple cup of coffee a day can do more than just wake you up in the morning. A new study suggests that regular coffee consumption may be linked to differences in the functioning of the digestive system.
Researchers from the University of Copenhagen examined 61 healthy adults to study the impact of coffee consumption on the gut. In addition to confirming that people who frequently drank coffee had a greater diversity of microorganisms in their gut than occasional drinkers, the results also revealed that regular coffee consumption appeared to affect the physiology of the gut itself.
The research team followed the participants for nine consecutive days. The volunteers recorded everything they ate and drank for eight days, while the researchers assessed their coffee intake using dietary data and caffeine-related substances found in urine.
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Fifty participants also swallowed a wireless capsule known as the SmartPill, which, as it moved through the digestive system, recorded information about transit time, temperature, acidity (pH), pressure and intestinal contractions.
This allowed scientists to examine how the digestive tract works.
Participants were divided according to their coffee habits. Frequent drinkers were defined as those consuming between one and five cups per day on more than three of the eight recorded days. The remaining participants were classified as less frequent coffee drinkers.
The results, published in Intestinal microbiologyfound that frequent coffee drinkers had significantly lower pH levels in their small intestines. They also showed an association between greater coffee consumption and more frequent colon contractions.
These contractions, according to first author Francesca Bucci, a doctoral student at the Department of Nutrition, Exercise and Sport at the University of Copenhagen, can promote healthy digestion, help prevent constipation and keep intestinal muscles in good condition.
“Frequent coffee consumption appears to affect the physiology of the gut itself, in other words how it functions,” she said.
The significance of the lower pH of the small intestine remains unclear. Researchers have not established whether it is beneficial or harmful, although acidity is known to influence digestive enzymes and the breakdown of food.
Despite the differences observed, the researchers caution that their results cannot prove that coffee directly caused the changes. However, lead author Henrik Munch Roager, associate professor and head of the research group in the Department of Nutrition, Exercise and Sport, believes there is good reason to believe that coffee plays a key role.
“We already know from other studies that coffee can influence a range of processes in the digestive system, including the secretion of acid in the stomach. So there is good reason to believe that what we are seeing is not just a coincidence. Anecdotally, many people also report that coffee affects their digestion,” he said.
What exactly is behind the increased colon contractions is also not resolved. “This could be due to either signaling from the stomach to the colon via the nervous system, or coffee molecules interacting locally with cells in the colon, thereby stimulating contractions. Caffeine could be involved, but coffee contains hundreds of bioactive molecules, which could also be involved – this remains unresolved,” Roager said. News week.
Dr. Dan Carter, Director of Neurogastroenterology at Sheba Medical Center, said: News week that the effects of coffee on the gut go beyond caffeine.
“Coffee is much more than caffeine. It contains hundreds of biologically active compounds, including polyphenols, which can influence the bacteria in our guts, collectively known as the gut microbiome.
“Studies show that coffee can stimulate colon contractions, sometimes within just a few minutes. Interestingly, decaffeinated coffee can produce a similar effect, although regular coffee may be slightly stronger,” Carter said.
Although the exact mechanism is not fully understood, one potential explanation is the gastrocolic reflex, the natural increase in intestinal activity that can occur after eating or drinking.
“Coffee appears to stimulate communication between the stomach, nervous system and colon, possibly through digestive hormones and what we call the gastrocolic reflex, the natural increase in intestinal activity after eating or drinking.”
But according to Carter, it’s not yet clear whether these physiological and microbial changes ultimately mean better digestive health.
Roager said further research should involve controlled experiments comparing gut activity during periods when participants consume coffee and periods when they do not.
Researchers hope that a better understanding of coffee’s effects on bowel movements could eventually contribute to new approaches to digestive problems.
“Many people suffer from constipation and irregular bowel movements. If we can understand how coffee affects digestion and intestinal contractions, it may be possible to use this knowledge to stimulate intestinal motility naturally. This would be extremely valuable,” Roager said.
According to Carter, while there is reasonably strong evidence that coffee can stimulate bowel contractions, the evidence that it effectively treats chronic constipation is much less convincing.
He said that although trials involving patients recovering from abdominal surgery have shown that coffee can help a faster return of bowel function, this does not prove that daily coffee consumption treats chronic constipation.
“We still lack large-scale, well-designed clinical trials demonstrating consistent, long-term benefit for patients with constipation.”
He also emphasized that while he does not discourage coffee consumption in patients who benefit from it, he would not recommend it as a substitute for established treatments, particularly for patients with persistent or severe constipation.
“My general advice is simple,” he said, “if you enjoy coffee, tolerate it well, and it helps you maintain regular bowel movements, there’s usually no need to stop. But if it causes urgency, discomfort, or diarrhea, reducing your intake or switching to decaf may be worth it. As with many aspects of digestive health, individual answers matter more than any universal rule.”
Roager said the findings could help focus research on the specific components of coffee that could be responsible.
“I hope our results will stimulate more interest and research into determining which bioactive molecules in coffee might interact with intestinal motility, as this knowledge could inform new solutions targeting constipation.”
Reference:
Bucci et al. Habitual coffee consumption is linked to differences in gut microbiota and physiology. Intestinal microbiology. DOI: 10.1016/j.gutmic.2026.100018
Contact Newsweek editors about this story: Kara Dolman And Paul Donnelley.
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