University of Copenhagen study: coffee alters gut physiology and microbiome

Regular coffee consumption is capable of altering not only the microflora but also the physiology of the gastrointestinal tract itself. This conclusion was drawn by researchers at the University of Copenhagen, whose work was published in the journal Gut Microbiology. These findings could be a step towards developing more effective methods for combating constipation.

How the measurements were conducted

The team of scientists recruited 61 healthy adult participants from Denmark. Each of them had to swallow a small electronic capsule. As it passed through the digestive tract, the device recorded transit time, temperature, pH levels, and the nature of intestinal contractions.

Participants were divided into two groups. The first group consisted of frequent coffee consumers — those who drank between one and five cups daily for more than three out of the eight days of the study. The second group comprised people who drank coffee less frequently.

Impact on the microbiome and organ function

First and foremost, the results confirmed previous hypotheses regarding coffee's impact on bacterial composition. Frequent consumers exhibited greater diversity of microorganisms compared to infrequent consumers.

However, as noted by the study's first author, PhD student at the Department of Nutrition, Exercise and Sports at the University of Copenhagen, Francesca Bucci, the key aspect is different:

"But perhaps more importantly, frequent coffee consumption appears to affect the physiology of the gut itself, meaning how it functions," says Francesca Bucci.

It has long been known that moderate coffee consumption is associated with a reduced risk of cardiovascular diseases, diabetes, depression, and certain types of cancer. However, the mechanism by which habitual coffee consumption affects the physiological state of the gut has been insufficiently studied.

Contractions and pH levels

Researchers found that frequent coffee consumers had significantly lower pH levels in the small intestine than those who drank coffee less frequently. It was also recorded that the more coffee consumed, the more intense the contractions in the large intestine.

Are these changes beneficial? Francesca Bucci explains:

"Intestinal contractions can support healthy digestion, help prevent constipation, and keep the gut muscles in good tone," says Bucci.

Regarding the lowered pH level, researchers cannot yet definitively say whether it brings benefit or harm. At the same time, it is known that this indicator plays an important role in the activity of digestive enzymes and the breakdown of food.

Causes and consequences

Scientists emphasise that this study cannot prove that all observed differences are caused exclusively by coffee. However, the study's senior author, associate professor and head of the research group at the Department of Nutrition, Exercise and Sports, Henrik Munk Roager, believes there are grounds to consider coffee a key factor.

"For example, other studies have already shown that coffee can affect a number of processes in the gastrointestinal system, including acid secretion in the stomach. Therefore, there are all the grounds to believe that what we are observing is not just a coincidence. According to anecdotal observations, many people also report that coffee affects their digestion," says Roager.

Further research needed

In Roager's opinion, the next logical step should be an interventional study. In it, scientists will control the amount of coffee participants drink and investigate how gut physiology changes during periods of intensive coffee consumption compared to periods without it.

Researchers hope that these and future findings will help solve a common problem.

"Many people suffer from constipation and irregular bowel movements. If we understand how coffee affects digestion and intestinal contractions, we may be able to use this knowledge to naturally stimulate gut motility. That would be extremely valuable," says Roager.