The Immune Mind: Linking Dietary Patterns, Microbiota, and Psychological Health
Abstract
Background/Objectives: Nutritional patterns influence the gut-brain axis and immune signaling with potential consequences for depression and anxiety. We conducted a review focused on clinically meaningful psychiatric outcomes (symptom severity/diagnosis) to synthesize recent evidence (2020-2025) on Mediterranean-style dietary interventions; ultra-processed food (UPF) exposure; and psychobiotic/prebiotic strategies, integrating mechanistic insights relevant to practice. Methods: Searches in PubMed/MEDLINE, Scopus, and Web of Science (January 2020-October 2025) combined terms for diet, Mediterranean diet (MD), UPF, microbiota, probiotics, psychobiotics, depression, and anxiety. Eligible designs were randomized/controlled trials (RCTs), prospective cohorts, and systematic reviews/meta-analyses reporting clinical psychiatric outcomes in adults. We prioritized high-quality quantitative syntheses and recent RCTs; data were extracted into a prespecified matrix and synthesized narratively. Results: Recent systematic reviews/meta-analyses support that MD interventions reduce depressive symptoms in adults with major or subthreshold depression, although large, long-term, multicenter RCTs remain a gap. Exposure to UPF is consistently associated with higher risk of common mental disorders and depressive outcomes in large prospective cohorts. Psychobiotics (specific probiotic strains and prebiotics) show small-to-moderate benefits on depressive symptoms across clinical and nonclinical…
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