Effects and Mechanisms of Probiotics, Prebiotics, Synbiotics, and Postbiotics for the Prevention and Management of Alzheimer’s Disease: A Narrative Review

Alzheimer's disease (AD) is a rapidly escalating global health crisis with limited effective treatments. Emerging research underscores the pivotal role of the microbiota-gut-brain axis in AD pathogenesis, prompting the exploration into gut microbiota-targeted interventions. This narrative review aimed to comprehensively synthesize the latest epidemiological, experimental, and clinical evidence regarding the effects and mechanisms of probiotics, prebiotics, synbiotics, and postbiotics (PPSPs) in AD prevention and management. We conducted a narrative review of relevant literature from the Web of Science and PubMed databases. The search focused on articles published within the last 5 years using keywords such as "Alzheimer's disease", "AD", "gut-brain axis", "gut microbiota", "probiotics", "prebiotics", "synbiotics", and "postbiotics". The findings suggest that PPSPs mitigate AD pathology and improve cognitive performance by modulating gut microbiota, strengthening intestinal barrier integrity, decreasing amyloid-beta (Aβ) deposition and tau hyperphosphorylation, reducing neuroinflammation and oxidative stress, regulating neurotransmitter metabolism, and promoting synaptic plasticity. Some studies also report varied outcomes, attributable to factors like strain specificity, dosage, intervention duration, patient heterogeneity, and methodological differences. In conclusion, targeting the microbiota-gut-brain axis with PPSPs offers a promising, mechanism-based strategy for AD, though further research is essential to optimize specific interventions for clinical application.