<![CDATA[Probiotic supplementation has gained increasing attention as a strategy to improve gut health by modulating the intestinal microbiota, strengthening the gut barrier, and regulating immune responses. However, probiotic efficacy is strain-specific, and evidence comparing the benefits of different probiotic species remains limited. This comprehensive review aimed to evaluate the effectiveness of specific probiotic strains in improving gut health and managing gastrointestinal disorders. A comprehensive literature search was conducted in PubMed, Scopus, and Web of Science using the keywords probiotics, gut health, microbiome, intestinal barrier, and gastrointestinal disorders. Following predefined eligibility criteria, clinical and experimental studies investigating strain-specific probiotic effects were screened. After full-text review, we included 12 relevant articles for qualitative synthesis. Data were evaluated according to probiotic strain, intervention characteristics, gut health outcomes, and proposed mechanisms. The findings indicate that probiotic efficacy depends on the strain. Lactobacillus species consistently improved intestinal barrier function and reduced diarrhea, whereas Bifidobacterium species enhanced microbial diversity and immune regulation. Saccharomyces boulardii demonstrated the strongest evidence for preventing antibiotic-associated diarrhea and recurrent gastrointestinal infections. Multi-strain formulations generally produced broader benefits than single-strain probiotics through complementary mechanisms. Both dairy- and plant-based probiotic formulations were effective delivery systems, although plant-based products are better suited to lactose-intolerant and vegan populations. In conclusion, probiotics provide measurable benefits for gastrointestinal health, but clinical outcomes depend largely on selecting appropriate strains. Current evidence supports Lactobacillus, Bifidobacterium, and Saccharomyces boulardii as the probiotic strains with the most consistent benefits for gut health. Further well-designed randomized controlled trials are needed to establish strain-specific clinical recommendations.]]>
