Safety and Effectiveness of Probiotic Preparations: A Contemporary Review.

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.