Coffee does more than keep us awake. A new study led by Professor John Cryan, from University College Cork, suggests that regular coffee consumption may influence the gut microbiota in ways that affect immune function, stress responses and gut-brain communication. By following habitual coffee drinkers through a period of coffee withdrawal and reintroduction, the researchers showed that removing coffee temporarily altered the gut microbiome, while reintroducing either regular or decaffeinated coffee helped restore many of these changes.
During his visit to Barcelona to speak at the Biomedical Research Symposium organized by the Department of Medicine and Life Sciences at Pompeu Fabra University (UPF), held at the PRBB Auditorium, the Gut Microbiota for Health team enjoyed a cup of coffee with Cryan while discussing his latest study and what it reveals about the role of coffee, caffeine and polyphenols in shaping the gut microbiota-brain axis.
Your latest study explores how coffee influences the gut microbiota-brain axis. What prompted you to investigate this relationship?
We became interested in coffee because it is rich in polyphenols, plant compounds that give many foods their colour. They’ve been shown to affect the composition of the microbiome and to be broken down by the microbiome. And we were interested to see how coffee through the polyphenols affect the microbiome in ways that affect communication between the gut and the brain.
You followed 30 habitual coffee drinkers as they stopped drinking coffee and then started again. What happened to their gut microbiota during that process?
We wanted to capture the entire journey: coffee consumption, withdrawal and reintroduction. That allowed us to observe what was happening to the gut microbiome throughout those different stages. One of the things we were able to show was that during coffee withdrawal there were changes not only in the microbiome but also in immune function, anxiety levels and some aspects of cognition. These changes appeared to occur together. When participants started drinking coffee again, many of those measures began to return towards normal. One of the biggest surprises was that reintroducing decaffeinated coffee produced similarly positive effects.
So caffeine wasn’t the main driver?
That’s one of our hypotheses. We think the effect may be driven by microbial signalling. Under normal circumstances, coffee polyphenols help nourish certain gut microbes and contribute to maintaining a stable dialogue between the gut and the brain. When that source of nutrition disappears during withdrawal, the microbial community changes and we begin to see more inflammatory responses. Of course, this was a relatively small study, so these findings now need to be confirmed.
Could other polyphenol-rich foods, such as dark chocolate, produce similar effects?
It would certainly be interesting to test that. My gut feeling is that they probably wouldn’t produce exactly the same effects because coffee contains a unique combination of polyphenols. These differ from those found in foods such as grapes, onions or green tea, and they may influence the microbiome in different ways.
Were there particular bacteria or microbial metabolites that stood out?
Yes. We identified several bacterial groups whose abundance consistently changed with coffee consumption, particularly Eggerthella and Cryptobacteria. We also observed changes in metabolites that are known to influence the enteric nervous system, including GABA and metabolites derived from tryptophan. As coffee was reintroduced, some tryptophan metabolites reappeared, together with short-chain fatty acids.
What do these findings tell us about coffee’s potential impact on health?
Our results fit with a growing body of research. Large population studies from Nicola Segata and other labs have also linked coffee consumption with changes in the gut microbiome that may benefit overall health. There is also emerging epidemiological evidence suggesting that people living with dementia tend to consume less coffee than those without dementia, raising the possibility that coffee could have a protective role in maintaining cognitive function as we age.
Based on your findings, would you recommend coffee as a dietary psychobiotic to benefit our daily mood and cognition?
If you’re already a moderate coffee drinker, I think our findings suggest that coffee could be beneficial for your microbiome and may have positive effects on gut-brain communication. What’s particularly interesting is that decaffeinated coffee appeared to produce similar effects. So people who want to reduce their caffeine intake may still be able to retain many of coffee’s potential benefits by combining regular and decaffeinated coffee throughout your day.
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