Lactiplantibacillus plantarum Probio87 improves functional constipation through the gut microbiota–bile acid axis: a randomized controlled trial

Background: Functional constipation (FC) is a common gastrointestinal disorder that significantly impairs patients’ quality of life and psychological well-being. Gut microbiota dysbiosis and altered bile acid (BA) metabolism have been implicated in its pathogenesis, suggesting the therapeutic potential of probiotics. This randomized, double-blind, placebo-controlled trial evaluated whether Lactiplantibacillus plantarum Probio87 could alleviate FC symptoms by modulating the gut microbiota–bile acid axis, in combination with a comprehensive healthy lifestyle intervention. Results: A total of 101 adults with FC were randomly assigned to receive L. plantarum Probio87 (n = 51) or placebo (n = 50) for eight weeks. Compared with the placebo group, the intervention group showed a 1.89-fold increase in weekly complete spontaneous bowel movements (CSBM) at week 8 (p < 0.001), with improvements sustained at a four-week follow-up. L. plantarum supplementation also improved quality of life and psychological well-being scores. Metagenomic and metabolomic analyses revealed enhanced microbial diversity, enrichment of beneficial taxa such as Anaerostipes caccae and Fusicatenibacter saccharivorans, and significant upregulation of primary bile acid biosynthesis, particularly glycochenodeoxycholic acid (GCDCA) and glycocholic acid (GCA). Mediation analysis indicated that BA-related metabolites partially mediated the link between gut microbiota remodeling and symptom relief. Conclusions: The findings demonstrate that L. plantarum Probio87, in conjunction with a healthy lifestyle, effectively alleviates functional constipation by modulating the microbiota–bile acid–gut axis. The study provides mechanistic insight into the probiotic’s sustained clinical benefits and highlights the therapeutic relevance of targeting bile acid metabolism in managing FC.