Psychobiotics and Trace Elements in Neurodegenerative Diseases: From Independent Modulators to Potential Interactions Within the Microbiota–Gut–Brain Axis—Narrative Review

The microbiota–gut–brain axis represents an important bidirectional communication network linking the gastrointestinal tract and the central nervous system and may contribute to processes involved in neurodegeneration. Increasing attention has been directed toward psychobiotics as potential modulators of the microbiota–gut–brain axis, while accumulating evidence also indicates that disturbed trace-element homeostasis may contribute to the pathogenesis of neurodegenerative diseases. This review summarizes current evidence on the roles of psychobiotics and trace elements and examines their potential interplay within the microbiota–gut–brain axis. The review discusses bidirectional interactions between the gut microbiota and trace elements, the potential effects of psychobiotic interventions on trace-element homeostasis, and the possible implications of these interactions for neurodegenerative processes. Taken together, current findings indicate that the gut microbiota, psychobiotics, and trace elements may constitute an interconnected system influencing intestinal and systemic homeostasis as well as biological processes relevant to nervous system function. However, direct evidence demonstrating the clinical relevance of interactions between these components remains limited. Moreover, available evidence is largely based on experimental studies, while clinical findings remain scarce and heterogeneous. Further characterization of this interplay may improve our understanding of mechanisms underlying neurodegeneration and provide a basis for the development of more targeted and personalized approaches to supporting neurological health.