A new study from a team at University College Cork, part of the National University of Ireland, found that both caffeinated and decaffeinated coffee positively change the gut microbiome — and that those changes reduce stress and improve psychological well-being.
contains a wide range of biologically active compounds. These include alkaloids such as caffeine, polyphenols such as phenolic acids, and organic compounds like diterpenes and melanoidins that form during roasting.
Moderate coffee consumption has been linked to a lower risk of developing chronic conditions such as:
- liver disease
- cardiovascular disease
- some types of .
Drinking coffee has been consistently linked to a lower risk of developing Parkinson’s disease. Regular coffee consumption reduces the incidence of Alzheimer’s disease by 27 percent. People who enjoy this beverage report lower rates of depression.
What the study found about coffee, the gut, and mood
In the new study, Professor John Cryan’s team examined how drinking coffee, stopping coffee, and then resuming coffee affected cognitive function, , and behavior in the context of the gut–brain connection.
Researchers analyzed data from 62 people. Half the participants drank coffee; the other half did not (control group). Volunteers regularly completed psychological tests, kept food and caffeine diaries, and provided biological samples for analysis. The scientists’ goal was to detect changes in the microbiome and in stress levels.
Participants in the coffee group were people who regularly drank 3–5 a day. The European Food Safety Authority (EFSA) considers this amount safe and moderate for most people.
First, participants abstained from coffee for two weeks. The coffee withdrawal period in regular coffee drinkers coincided with significant changes in the gut microbiota metabolite profiles compared with the non–coffee drinkers.
Then the coffee drinkers were allowed to resume their usual beverage. Half of them drank decaf, and the other half drank caffeinated coffee. In the end, both groups reported lower levels of , depression, and impulsivity. That points to a clear improvement in participants’ moods from drinking coffee — regardless of caffeine content — and to an overall strengthening of mental health.
The team published their findings in the journal Nature Communications. People who drank coffee showed a notable increase in the bacteria Eggerthella sp. and Cryptobacterium curtum, which positively influence the gut–brain axis. These bacteria also play an important role in eliminating harmful gut bacteria and stomach infections. The coffee drinkers’ microbiomes also showed an increase in Firmicutes bacteria, which are associated with positive emotions in women.
Interestingly, the researchers found noticeable improvements in learning and memory among the participants who drank decaf. Meanwhile, drinking caffeinated coffee was linked with:
- improved alertness and attention
- reduced feelings of anxiety
- a lower risk of inflammation.
The team says people are increasingly thinking about changing their diets to support proper digestion. Coffee could be an additional component of a balanced diet.
“Our results show how the microbiome and the nervous system respond to coffee, and the potential long-term benefit of coffee for improving microbiome health,” said Professor John Cryan.
As the lead author emphasized, coffee is a complex dietary factor that interacts with “the flora of our gut, metabolism, and even emotional state.”
Photo: Unsplash
