Safety Assessment of Probiotics and Postbiotics: A Critical Review

Probiotics and postbiotics are essential components of modern dietary supplements, recognized for their beneficial effects on human health. While probiotics positively influence gut microbiota, digestion, and immune responses, their safety remains a concern, particularly in immunocompromised individuals, due to risks such as infections, transfer of antibiotic resistance genes, and systemic complications. In contrast, postbiotics-defined as inanimate microorganisms and/or their cellular components-offer a safer alternative by providing similar health benefits without the risks associated with live microorganisms. However, safety assessments of postbiotics remain limited and must address critical issues such as cytotoxicity, impurity profiles, and dose-response uncertainties, which are currently underexplored in the literature. Their enhanced stability under various environmental conditions further supports their application in inhibiting foodborne pathogens and extending product shelf life. This review critically evaluates the safety profiles of probiotics and postbiotics, offering a balanced analysis of their benefits and limitations, with particular attention to emerging safety concerns, risk assessment criteria, and applications in food safety and human health. Despite their promising safety profile, widespread adoption of postbiotics is hindered by the absence of standardized safety protocols and long-term toxicological data. Future research should therefore prioritize establishing evidence-based safety criteria, optimizing dosage and formulation for both probiotics and postbiotics, and addressing existing knowledge gaps through rigorous, targeted clinical studies, especially in vulnerable populations. A comprehensive literature search was conducted using the ISI Web of Knowledge, PubMed, Medline, Embase, Cochrane Register of Controlled Trials (CENTRAL), and Scopus databases covering the period from 2000 to 2025.