Study Links Regular Coffee Intake to Changes in Gut Microbiome and Intestinal Activity
Researchers at the University of Copenhagen found that frequent coffee drinkers have a more diverse gut microbiota, lower small-intestine pH and increased colon contractions, though the health implications remain uncertain.
A study of 61 healthy adults conducted by the University of Copenhagen examined how habitual coffee consumption influences the gut. Participants recorded their diet for eight days while researchers measured coffee intake through dietary logs and urinary caffeine metabolites. Fifty volunteers also swallowed a wireless SmartPill capsule that tracked transit time, temperature, acidity, pressure and intestinal contractions.
Frequent coffee drinkers—defined as those consuming one to five cups per day on most recorded days—showed a higher diversity of gut microorganisms compared with less frequent drinkers. The study, published in Gut Microbiology, also reported that frequent drinkers had significantly lower pH levels in the small intestine and more frequent colon contractions.
"Frequent coffee consumption appears to affect the physiology of the gut itself, in other words how the gut functions," said Francesca Bucci, a PhD student and first author of the paper.
"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," said senior author Henrik Munch Roager, associate professor and research group leader.
The researchers noted that the lower small-intestine pH could affect digestive enzymes, but its health impact is unclear. Roager suggested that coffee’s effect on colon contractions might involve neural signaling or direct interaction of coffee compounds with colonic cells, and that caffeine could be one of many bioactive molecules involved.
Dr. Dan Carter, director of neurogastroenterology at Sheba Medical Center, emphasized that coffee contains numerous biologically active compounds beyond caffeine, which may influence the gut microbiome and stimulate colon activity. He added that while coffee can prompt bowel movements, evidence that it treats chronic constipation is limited.
Both researchers called for controlled experiments comparing gut activity during periods of coffee consumption and abstinence, and suggested that identifying specific coffee components responsible for the observed effects could inform new approaches to managing constipation and irregular bowel movements.