Researchers at University College Cork published a study in Nature Communications in April revealing that both caffeinated and decaffeinated coffee alter gut microbes and improve specific cognitive and mood measures. In a small experiment with 31 habitual coffee drinkers, only participants who drank decaffeinated coffee showed significant improvements on two memory tests after a two-week withdrawal period and a three-week reintroduction.
APC Microbiome Ireland Experiment Details
The study tracked 31 regular coffee drinkers who typically consumed three to five cups daily, alongside 31 non-consumers. Researchers used diaries of consumption, urine tests, psychological tests, and stool samples to monitor the groups. Participants stopped drinking coffee for two weeks, which triggered substantial shifts in their stool sample gut microbe profiles. The research was sponsored by the Scientific Information Institute on Coffee and conducted through APC Microbiome Ireland. After the withdrawal phase, participants received coffee for three weeks without knowing whether they were assigned the caffeinated or decaffeinated version.
Observed Changes in Mood and Stress
Reintroducing coffee brought noticeable psychological shifts across both groups. Participants reported lower perceived stress, depression, and impulsivity after resuming coffee drinking. Caffeinated coffee improved anxiety and some aspects of cognitive performance, while decaffeinated coffee reduced emotional reactivity and was linked to better sleep quality and increased physical activity. However, only the decaf group achieved measurable gains on word-learning and location-memory tests. The decaf group made fewer errors on the location test and improved on several parts of the word test, while the caffeinated group showed no significant improvements on these specific memory tasks.
Gut bacteria process coffee compounds along gut brain axis
John Cryan, a stress neurobiologist at University College Cork who co-coined the term psychobiotics in 2013, explained that coffee acts as a complex dietary factor interacting with the gut-brain axis. Signals between these systems can move via nerves, hormones, the immune system, and chemicals created when gut microbes process drinks and food. Bacteria associated with gastric acid secretion, bile acid synthesis, and Firmicutes increased in coffee consumers compared to non-consumers. In women, the increase in Firmicutes was associated with positive emotions.
Non caffeine compounds influence brain function and mood
The study found that caffeine-related chemicals were present in the caffeinated group, but phenolic compounds related to coffee changed for participants regardless of whether they drank decaf or caffeinated versions. These non-caffeine compounds are processed by gut bacteria into metabolites that may influence brain function, mood, and inflammation.
Small study links decaf coffee to better memory
Did the study prove that decaf coffee improves memory?
In this specific experiment of 31 participants, only those who drank decaffeinated coffee showed significant improvements on word and location memory tests. Scientists note the study is small and preliminary, meaning the findings require further research to confirm.
What limits apply to these findings?
The study involved a small sample of healthy adults, and improvements could potentially link to better sleep, increased physical activity, or familiarity with the tests. Researchers emphasized the data shows statistical links rather than direct cause-and-effect proof.
Can coffee replace professional mental health care?
The findings do not suggest that coffee can prevent depression, treat anxiety, or replace professional care, nor do they imply that everyone should start drinking several cups a day. As John Cryan stated, coffee also has the potential to be leveraged as an additional intervention within a healthy and balanced diet
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