Effects of Two Compound Probiotic Formulations on Gastrointestinal Symptoms and Gut Microbiota: A 4-Week Randomized, Double-Blind Intervention Trial

Background/Objectives: Probiotic interventions can alleviate gastrointestinal (GI) discomfort, but evidence comparing multi-strain combinations at different doses remains limited. We evaluated whether formulation potency influences clinical and microbiome outcomes. Methods: In a 4-week, randomized, double-blind trial, 100 eligible adults received one of two higher-dose multi-strain probiotic formulations at different dosages (Wec120B vs Wec300B). Weekly Gastrointestinal Symptom Rating Scale (GSRS) scores tracked symptom trajectories. Gut microbiota composition and diversity were profiled by 16S rRNA gene sequencing. Biomarkers included lipopolysaccharide (LPS), fecal calprotectin (FC), and immunoglobulin A (IgA). Results: Results indicated that the Wec120B group showed more significant improvement in abdominal pain during the early phase of intervention, while the Wec300B group was more effective in relieving reflux symptoms. In terms of biomarkers, Wec120B was more effective in reducing lipopolysaccharide (LPS) levels, whereas Wec300B showed a greater increase in immunoglobulin A (IgA) and a more pronounced reduction in fecal calprotectin (FC) levels. Both formulations significantly increased the abundance of beneficial genera such as Bifidobacterium, Blautia, Eubacteriumₕalliigroup, and Anaerostipes, while suppressing the growth of potential pathogens including Prevotella and Escherichia-Shigella. Conclusions: These findings suggest that both compound probiotic products can significantly improve GI symptoms and modulate gut microbiota structure, with Wec300B showing a superior performance in microbial regulation, likely due to its higher dosage of probiotics. This study provides reference evidence for the rational application of probiotic products in gut health management.