Background/Objectives: Probiotic preparations have attracted increasing attention because of their potential to modulate the gut microbiota and improve health outcomes in a wide range of gastrointestinal and extraintestinal diseases. However, their efficacy and safety are strain-specific and remain inconsistent across many clinical indications. The aim of this review was to evaluate current evidence regarding the efficacy, safety, mechanisms of action, and clinical applications of probiotic preparations. Methods: A narrative literature review was conducted using the PubMed, Scopus, and Web of Science databases to identify publications addressing the efficacy, safety, and clinical applications of probiotic preparations. The literature search was last updated in July 2026. No publication-year restrictions were applied; the studies included in this review were published between 2000 and 2026. Priority was given to systematic reviews, meta-analyses, randomized controlled trials, international clinical practice guidelines, and mechanistic studies. Results: The reviewed evidence indicates that probiotics may contribute to intestinal homeostasis through modulation of the gut microbiota, enhancement of intestinal barrier function, and regulation of immune responses. The strongest evidence supports the use of selected probiotic strains for the prevention of antibiotic-associated diarrhea, whereas evidence for the prevention of necrotizing enterocolitis is generally favorable but depends on the specific probiotic preparation, product quality, and clinical setting. Evidence for most other gastrointestinal and extraintestinal disorders remains heterogeneous and strain-specific. Although probiotics generally exhibit a favorable safety profile, rare infectious complications have been reported in high-risk patients. Conclusions: Current evidence indicates that the efficacy and safety of probiotics depend on the specific strain, clinical indication, and patient characteristics. Further high-quality, strain-specific clinical studies are needed to optimize their use in medical practice.

Background/Objectives: Intestinal diseases constitute a significant global public health issue and encompass a broad spectrum of inflammatory, functional, and infectious disorders, including inflammatory bowel disease (Crohn’s disease and ulcerative colitis) and irritable bowel syndrome. In recent years, increasing attention has been paid to sex-related differences in epidemiology, clinical course, diagnosis, and treatment outcomes. Methods: A structured narrative review was conducted using the PubMed, Scopus, and Web of Science databases to identify publications addressing sex-related differences in the epidemiology, pathophysiology, diagnosis, and treatment of intestinal diseases. The aim of the study was to examine sex-based differences in the etiology, diagnosis, and treatment of intestinal diseases. Results: The development of intestinal diseases is determined by the interaction of genetic, immunological, hormonal, microbial, and environmental factors. Sex-related differences were identified in disease prevalence, clinical course, and progression and are associated with hormonal regulation, immune response characteristics, and gut microbiota composition. Diagnosis of intestinal diseases is based on a combination of laboratory biomarkers, endoscopic, and imaging techniques, and diagnostic accuracy may vary according to biological sex. Video capsule endoscopy, balloon-assisted enteroscopy, and advanced imaging methods, including computed tomography colonography, improve the evaluation of small bowel diseases, whereas chromoendoscopy, colonoscopy, and cross-sectional imaging play important roles in the assessment of colonic disorders. Treatment includes pharmacological, dietary, microbiota-based, endoscopic, and surgical approaches. Current evidence suggests that biological sex may influence treatment response, adverse event profiles, and clinical outcomes; however, the available evidence remains limited or inconsistent for several therapeutic strategies, highlighting the need for further sex-specific clinical research. Conclusions: Sex-related differences should be considered to improve diagnostic accuracy, optimize treatment strategies, and support individualized clinical management. Although evidence remains limited in several areas, current findings support the integration of biological sex into clinical decision-making. Further research is needed to establish sex-specific diagnostic and therapeutic approaches.