Coffee may influence mood and brain function by altering the activity of microbes in the gut, according to a new study that examined both caffeinated and decaffeinated varieties. The research links coffee consumption to lower levels of stress, depression, and impulsivity, while also documenting measurable changes in gut bacteria and the metabolites they produce.
The findings suggest that the beverage's effects on the brain may not be driven by caffeine alone. Both regular and decaf coffee were associated with the same broad pattern of reduced stress, depression, and impulsivity, pointing to compounds in coffee or the gut microbiome itself as possible mediators of the effect.
According to the study, the two types of coffee diverged in their associations with specific cognitive outcomes. Decaffeinated coffee was linked to better learning and memory, while caffeinated coffee appeared to reduce anxiety and improve attention. The results indicate that caffeine and decaf may shape brain function through different pathways, even as both influence the gut environment.
The research adds to a growing body of work on the gut-brain axis, the bidirectional communication system that connects the digestive tract and its resident microbes with the central nervous system. Changes in gut bacteria and their metabolites have been increasingly studied for their potential role in mood regulation, cognitive performance, and mental health.
In this study, the measurable shifts in gut bacteria and metabolites accompanied the reported differences in stress, depression, impulsivity, learning, memory, anxiety, and attention. The authors suggest that coffee may exert its effects on mood and brain function at least in part by changing the activity of gut microbes, rather than through a direct action on the brain alone.
The findings could help explain why coffee has been associated with a range of psychological and cognitive outcomes in previous research, and why decaf sometimes produces effects similar to those of the caffeinated version. If gut microbes are involved, the beverage's impact on mental health and cognition may depend on how it reshapes the microbial community and the chemical signals that community produces.
The study does not establish that coffee causes these changes, only that the consumption of both caffeinated and decaffeinated coffee was linked to them. Further research would be needed to determine whether the microbial shifts are responsible for the observed differences in mood and cognition, and whether specific compounds in coffee drive the effect.
For now, the results point to the gut as a potentially important intermediary between coffee and the brain. They also suggest that decaffeinated coffee is not merely a substitute for the caffeinated version but may have its own distinct relationship with learning and memory, while caffeinated coffee may be more closely tied to reduced anxiety and improved attention.
The study's authors report that both types of coffee were associated with lower stress, depression, and impulsivity, alongside the changes in gut bacteria and metabolites. The cognitive associations differed by beverage type, with decaf linked to better learning and memory and caffeinated coffee linked to less anxiety and better attention.