Pioneering investigations spearheaded by researchers at University College Cork indicate that both regular and decaffeinated coffee varieties can modulate the gut microbiome in ways associated with diminished stress levels and enhanced psychological welfare, thereby illuminating the beverage’s long-hypothesized health advantages.
Boscaini et al. have elucidated previously undocumented impacts of coffee on the intricate microbiota-gut-brain communication network. Their work suggests that an individual’s microbiome composition might serve as an indicator of their coffee consumption habits and underscores a profound connection between coffee ingestion and the constitution of gut microbial communities. Image courtesy of Sci.News.
Coffee, a beverage derived from processed coffee beans, possesses a flavor and chemical makeup influenced by a multitude of variables, encompassing the specific varietal of the bean, its stage of ripeness, the methods employed for processing and roasting, and the techniques used for its preparation.
This popular drink is replete with a diverse array of biologically active constituents, including alkaloids like caffeine, polyphenols such as phenolic acids, diterpenes, and melanoidins, which are synthesized during the roasting process.
Consuming coffee in moderate quantities has been correlated with a reduced incidence of various chronic ailments, such as type 2 diabetes, hepatic conditions, cardiovascular disturbances, and certain oncological diagnoses.
Furthermore, a higher consumption rate has been consistently associated with a diminished risk of Parkinson’s disease, a correlation observed to be dose-dependent.
Individuals who regularly drink coffee exhibit a lower propensity to develop depression, and one analytical study posited that consistent intake was linked to a 27% reduction in the occurrence of Alzheimer’s disease.
In a recent investigation, Professor John Cryan of University College Cork, along with his research associates, scrutinized the ramifications of coffee consumption, cessation, and subsequent reintroduction on cognitive functions, emotional states, and behavioral patterns within the framework of the microbiota-gut-brain axis — the reciprocal signaling pathway between the intestinal microbiome and the brain.
The research team enlisted 31 habitual coffee consumers and 31 individuals who abstained from coffee. Participants underwent a series of psychological evaluations, maintained detailed records of their caffeine and food intake, and provided stool and urine samples to facilitate an understanding of their microbiome transformations and subjective experiences of mood and stress.
Habitual coffee drinkers were characterized as individuals who typically ingest 3-5 cups of coffee daily, a quantity deemed safe and moderate for the majority of the populace by the European Food Safety Authority (EFSA).
Initially, all participants were instructed to abstain from coffee for a fortnight, during which regular psychological assessments were conducted, alongside the collection of stool and urine specimens.
This period of coffee abstinence for the regular consumers was accompanied by discernible alterations in the metabolite profiles of their gut microbiomes, particularly when contrasted with the non-coffee drinking cohort.
Subsequently, coffee was reintroduced to the regular consumers under blinded conditions, with half receiving decaffeinated coffee and the other half consuming caffeinated coffee.
Both participant groups reported a reduction in their perceived stress, depression, and impulsivity scores, suggesting that the act of drinking coffee significantly contributed to an improved mood, independent of its caffeine content.
Specific bacterial species, such as Eggertella sp. and Cryptobacterium curtum, showed a notable proliferation in coffee drinkers compared to their non-drinking counterparts.
The former is believed to play a role in stimulating gastric and intestinal acid secretion, while the latter is thought to be implicated in the synthesis of bile acids; both processes may contribute to the eradication of detrimental gut bacteria and the prevention of stomach infections.
An increase in Firmicutes bacteria was also observed, a type of bacteria that has been associated with the manifestation of positive emotions in female subjects.
A significant enhancement in learning and memory capabilities was exclusively identified in individuals who consumed decaffeinated coffee, pointing towards the involvement of non-caffeine constituents, such as polyphenols, in mediating these cognitive advantages.
Conversely, the research scientists ascertained that only caffeinated coffee was linked to decreased sensations of anxiety, alongside augmented vigilance and attentional capacity. Caffeine was also correlated with a reduced susceptibility to inflammatory processes.
“There has been a substantial surge in public interest concerning gut health,” remarked Professor Cryan.
“While the interconnectedness of digestive and mental well-being is becoming increasingly recognized, the precise mechanisms underlying coffee’s influence on this gut-brain axis have remained elusive.”
“Our findings shed light on the microbiome and neurological responses elicited by coffee, as well as their potential long-term contributions to a healthier gut environment.”
“Coffee may exert influence over the collective activities of microorganisms and the metabolites they process.”
“As the public continues to contemplate dietary adjustments for optimal digestive equilibrium, coffee holds the potential to be integrated as an additional intervention within the scope of a healthy, balanced diet.”
“Coffee is more than merely a source of caffeine; it represents a complex dietary factor that interfaces with our gut microbiota, our metabolic processes, and even our emotional state.”
“Our discoveries indicate that coffee, regardless of whether it contains caffeine, can impact health through distinct yet complementary pathways.”
The research team’s conclusions are published today in the esteemed journal Nature Communications.
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S. Boscaini et al. 2026. Habitual coffee intake shapes the gut microbiome and modifies host physiology and cognition. Nat Commun 17, 3439; doi: 10.1038/s41467-026-71264-8
