Study:  Regular coffee drinkers had more colon contractions and more varied gut bacteria, a small Danish study finds

People who drink coffee regularly had more varied gut bacteria and more muscle contractions in the colon, which can help prevent constipation, than people who drank it less often, according to a University of Copenhagen study announced Nov. 10.  The researchers say the finding could someday help doctors treat constipation.

Frequent coffee drinkers also had a more acidic small intestine.  The researchers say they cannot yet tell whether that is good or bad, though acidity there affects how digestive enzymes break down food, the university says.

“Contractions in the gut can support healthy digestion, help prevent constipation and keep the intestinal muscles in good condition,” said first author Francesca Bucci, a Ph.D. student at the university.

What it means

The study offers one explanation for why many people say a cup of coffee “gets things moving,” the university says.  If future trials confirm the link, the knowledge might be used “to stimulate gut motility in a natural way,” meaning to help the gut move food along, which “would be extremely valuable” for the many people who struggle with constipation, said senior author Henrik Munch Roager.  Earlier research has tied moderate coffee drinking to a lower risk of heart disease, diabetes, depression and several types of cancer, the university notes, but much less is known about what coffee does inside the gut.

What you can do

• Don’t start drinking coffee as a treatment yet:  The researchers say this study cannot prove coffee caused the differences, and the next step is a trial that controls how much coffee people drink.
• If you drink coffee, keep it moderate:  For most adults, the U.S. Food and Drug Administration cites 400 milligrams of caffeine a day, about two to three 12-ounce cups of coffee, as an amount not generally linked to harmful effects.  People who are pregnant, trying to become pregnant or breastfeeding, or who take certain medicines, should ask a health care provider, the FDA says.
• For constipation, start with fiber and fluids:  Adults should get 22 to 34 grams of fiber a day from foods such as whole grains, beans, fruits, vegetables and nuts, adding it a little at a time and drinking plenty of water and other liquids, according to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), the federal agency that studies digestive health.
• Cut back slowly if you want less caffeine:  The FDA says cutting back gradually is best, because caffeine withdrawal is not dangerous but can be unpleasant.

What the study did

Sixty-one healthy Danish adults recorded everything they ate and drank for eight days.  Fifty of them swallowed a pill-sized wireless capsule that measured acidity, temperature, pressure, contractions and how long food took to pass through the gut.  Researchers checked urine for caffeine byproducts and tested stool for bacteria.  “Frequent” drinkers had one to five cups a day on more than three of the eight days.  The study appears in the journal Gut Microbiology.

What it did not show

The study is small and observational, so it cannot prove coffee caused the differences, the researchers say.  Senior author Henrik Munch Roager, an associate professor, says the next step is a trial that controls how much coffee people drink.  The university’s announcement does not say who paid for the study.

If you have ongoing constipation or other digestive trouble, talk with a doctor before changing what you drink.

Source:  University of Copenhagen news release, Nov. 10, 2026 on Bucci et al., Gut Microbiology; FDA:  How much caffeine is too much? and NIDDK:  eating, diet and nutrition for constipation, checked Nov. 12, 2026.