Probiotic Bifidobacterium bifidum BGN4 supplementation modulates gut microbiome composition and reduces circulating zonulin, TNFα, and insulin in adults with excess adiposity: a randomized, double-blind, placebo-controlled trial

BACKGROUND: Obesity, characterized by excess body fat accumulation, is closely linked to the alteration of gut microbiota, which contribute to systemic inflammation. Probiotics intervention has emerged as a promising strategy favorably modulating gut microbiota composition in obese individuals accompanied by improvements in metabolic parameters. The objective of this study was to evaluate whether supplementation with Bifidobacterium bifidum BGN4 alters gut microbiota composition and to assess its associated effects on circulating zonulin, a marker of intestinal permeability, as well as metabolic parameters in individuals with excess adiposity. METHODS: colony forming unit) or matched placebo for 8 weeks. Blood samples were analyzed for zonulin, TNFα, hs-CRP, glucose, insulin, lipid profiles, and total antioxidant capacity. Fecal samples were analyzed to determine alterations in gut microbiota composition. RESULTS: A total of 58 participants, with 29 individuals in each group, successfully completed the 8-week intervention. Supplementation with B. bifidum BGN4 did not result in significant changes in BMI, body fat percentage, or the primary outcome, hs-CRP. In contrast, significant improvements were observed in serum zonulin (between-group differences: -1.61 ± 2.69 ng/mL), TNFα (between-group differences: -0.17 ± 0.26 pg/mL), and fasting insulin (between-group differences: -3.52 ± 10.25 μIU/mL). The probiotic intervention modulated the enrichment of several taxa, including Bacteroides coprocola, Bifidobacterium catenulatum group, Lactiplantibacillus plantarum group, and Prevotella stercorea. In addition, several microbial taxa demonstrated correlations with metabolic and inflammatory parameters. No adverse effects were observed, as indicated by stable liver enzyme concentrations, blood pressure, and gastrointestinal symptoms. CONCLUSION: The results indicate that B. bifidum BGN4 may serve as a preventive strategy for metabolic disorders in individuals with excess adiposity through the maintenance of gut microbial balance and intestinal barrier integrity thereby potentially mitigating inflammation and metabolic stress. TRIAL REGISTRATION: Clinical trial registration number: KCT0010817. Date of registration: July 28, 2025.