Non-Gastrointestinal Effect of Probiotics in Patients with Parkinson's Disease: A Systematic Review of Randomized Controlled Trials
Andrea Guadalupe Tec-Ojeda, Sergio Guillermo Cuevas-Carbonell, Javier Humberto Perera-Rios, María Luisa Ávila-Escalante, Liliana Mendieta, José L. Góngora-Alfaro, Irma Isela Aranda GonzálezIntroduction:
Parkinson’s Disease (PD) is a prevalent neurodegenerative disorder characterized by motor and non-motor manifestations that significantly impact quality of life. Increasing evidence suggests that alterations in the gut microbiota and the gut–brain axis may contribute to its pathophysiology. Although probiotics have been widely studied for gastrointestinal symptoms, their potential effects on non-gastrointestinal outcomes remain unclear. Therefore, this study aimed to systematically review the evidence from RCTs assessing the non-gastrointestinal effects of probiotic supplementation in patients with PD.
Methods:
A systematic search was conducted in PubMed, ScienceDirect, and ClinicalTrials databases. Seven RCTs involving a total of 475 participants with PD met the inclusion criteria.
Results:
Despite variability in probiotic strains and dosages, supplementation with ≥ 1 × 109 CFU of Lactobacillus spp. and Bifidobacterium spp. for 12 weeks was associated with improvements in depression and anxiety symptoms, as well as reductions in inflammatory markers and insulin resistance in some studies. However, findings were inconsistent across studies, and no significant effects were observed on motor symptoms.
Discussion:
These findings suggest that probiotics may exert beneficial effects beyond gastrointestinal outcomes, potentially through modulation of the gut–brain axis, systemic inflammation, and metabolic pathways. However, heterogeneity in study designs and strains limits generalizability. Further high-quality, long-term RCTs are needed to confirm efficacy, clarify mechanisms, and establish clinical recommendations.
Conclusion:
Probiotic supplementation appears to offer promising non-gastrointestinal benefits for individuals with PD, but evidence remains preliminary.