PD, a neurodegenerative disorder with motor and non-motor symptoms, is linked to the gut microbiome. FMT can modify gut bacteria, but its effectiveness in PD remains uncertain.

PubMed, Embase, and Cochrane Library were searched up to September 2024. Risk Ratios (RR) and Mean difference (MD) were pooled for dichotomous and continuous outcomes using Review Manager version 5.4.1. Primary outcomes were changes in the Movement Disorder Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS) Parts I and II. Secondary outcomes included MDS-UPDRS Parts III (on and off medication) and IV, Irritable Bowel Severity Scoring System (IBS-SSS), Parkinson's disease Questionnaire-39 Summary Index (PDQ-39 SI), Montreal Cognitive Assessment (MoCA) scores, and gastrointestinal (GI) adverse events.

Three randomized trials pooling 145 PD patients were included in the analysis. FMT and placebo are comparable regarding MDS-UPDRS Part I (MD= -0.36; 95% CI:[-2.18,1.45];  p=0.70; I²=33%), Part II (MD=-0.46; 95% CI:[-1.91,0.99]; p=0.53; I²=0%), Part III (MD=1.41; 95% CI:[-2.14,4.42]; p=0.50; I²=17%), Part III off medication (MD=1.26; 95% CI:[-2.27,4.79]; p=0.48; I²=0%), and Part IV (MD= -0.39; 95% CI:[-1.63,0.85]; p=0.54; I²=24%). No significant changes were observed in IBS-SSS (MD=-15.91; 95% CI:[-63.17,31.89]; p=0.51; I²=76%), PDQ-39 SI (MD=-2.13, 95% CI:[-5.62,1.36]; p=0.23; I²=0%), and MoCA scores (MD=0.11; 95% CI:[-1.34,1.57]; p=0.88; I²=68%). However, gastrointestinal adverse events were more frequent in the FMT group (RR=3.32; 95% CI: [1.01,10.87]; p=0.05; I²=39%).

FMT showed no significant therapeutic effect on motor and non-motor symptoms of Parkinson’s disease compared to placebo, including no notable improvement in cognitive or gastrointestinal outcomes. However, it was associated with a higher frequency of gastrointestinal adverse events. Further research is needed to explore its potential therapeutic role in Parkinson's disease.