Probiotics in Alleviating Constipation: Mechanisms, Strain Screening, and Applications.

Constipation is a prevalent gastrointestinal disorder with limited effective therapeutic options. Probiotics have emerged as promising microecological interventions, yet marked strain-specific efficacy and incomplete mechanistic understanding hinder clinical translation. This review systematically synthesizes evidence from human randomized controlled trials, animal studies, and mechanistic investigations on probiotic interventions for constipation. We catalog major anti-constipation strains across Bifidobacterium, Lactobacillus, Bacillus, and other genera, and summarize key findings from published meta-analyses indicating that B. coagulans improves stool consistency by 52.8%, L. paracasei demonstrates 86.3% effectiveness for incomplete defecation severity and 87.6% for PAC-SYM, while L. reuteri achieves 99.9% effectiveness on PAC-QoL. Mechanistically, probiotics act through four synergistic pathways: gut microbiota modulation, metabolite-mediated actions centered on SCFAs and 5-HT-with strains harboring the abfA gene cluster exhibiting enhanced arabinan utilization for sustained metabolite production-gut-brain axis neuro regulation, and dynamic mucosal barrier restoration. Finally, we propose a systematic four-stage screening pipeline integrating genomic pre-screening, probiotic property evaluation, in vitro functional prediction, and in vivo multi-tiered validation. This review provides a comprehensive framework for evidence-based strain selection and personalized probiotic therapy in constipation management.