Psychobiotics: Mechanisms of Action, Evaluation Methods and Effectiveness in Applications with Food Products

The gut-brain-microbiota axis consists of a bilateral communication system that enables gut microbes to interact with the brain, and the latter with the gut. Gut bacteria influence behavior, and both depression and anxiety symptoms are directly associated with alterations in the microbiota. Psychobiotics are defined as probiotics that confer mental health benefits to the host when ingested in a particular quantity through interaction with commensal gut bacteria. The action mechanisms by which bacteria exert their psychobiotic potential has not been completely elucidated. However, it has been found that these bacteria provide their benefits mostly through the hypothalamic-pituitary-adrenal (HPA) axis, the immune response and inflammation, and through the production of neurohormones and neurotransmitters. This review aims to explore the different approaches to evaluate the psychobiotic potential of several bacterial strains and fermented products. The reviewed literature suggests that the consumption of psychobiotics could be considered as a viable option to both look after and restore mental health, without undesired secondary effects, and presenting a lower risk of allergies and less dependence compared to psychotropic drugs.