Impact of Gut–Brain Axis and Probiotics on Alzheimer’s Disease

This review explores links between the gut–brain axis, probiotics, and Alzheimer’s disease (AD). Using PRISMA-aligned methods, we examined literature from PubMed, ClinicalTrials.gov, and Google Scholar. Studies show that probiotics may reduce AD symptoms by modulating neuroinflammation, microbial composition, and neurotransmitter signaling. Probiotic strains such as B. breve and L. plantarum were found to be beneficial in early AD or mild cognitive impairment. Limitations include short intervention periods and strain variability. Clinical guidelines and research recommendations are discussed. Mechanisms involve immune signaling, neurotransmitter synthesis (GABA and serotonin), and modulation of systemic inflammation.