Postbiotics are defined as preparations of inanimate microorganisms and/or their components that confer a health benefit on the host. Although interest in postbiotics has increased substantially, their translational use in functional foods remains insufficiently characterized with respect to preparation identity, production methodology, food-matrix compatibility, mechanistic specificity, and regulatory positioning. This PRISMA-guided structured review aims to synthesize current evidence on postbiotics in functional food and nutraceutical contexts, with particular emphasis on preparation-based characterization, gut–brain axis-related mechanisms and clinical findings, food matrix applicability, and regulatory and health-claim considerations. Unlike broader postbiotic reviews that mainly address definitions, general health effects, or technological stability, this review integrates preparation identity, production process, gut–brain axis-related evidence, food matrix compatibility, and regulatory/health-claim translation within a single functional food framework. A structured literature search was conducted in Scopus and Web of Science Core Collection and was completed on 16 February 2026. The search strategy included three conceptual blocks: postbiotic and inactivation-based preparation terms, functional food/nutraceutical and food matrix terms, and gut–brain axis-related clinical and mechanistic terms. Cosmetic, topical, veterinary, animal feed, and aquaculture-focused publications were excluded. The export files contained 131 records from Scopus and 136 from the Web of Science Core Collection, yielding 267 records after applying document-type and language filters. After manually removing duplicates, 237 unique records were screened. Following title/abstract screening, 176 records were excluded as outside the scope of the review, and 61 publications were retained for full-text assessment and final thematic synthesis. The review was reported according to applicable PRISMA 2020 items. The evidence was organized into three thematic domains: gut–brain axis-related clinical findings, mechanistic evidence, and food matrix/product development applications. Heat-inactivated preparations, including Lactobacillus gasseri CP2305 and Lactiplantibacillus plantarum SNK12, have shown preliminary effects on stress-related symptoms, sleep quality, and selected neuroendocrine or inflammatory biomarkers in human studies. Mechanistic pathways include gut barrier integrity, immunomodulation, short-chain fatty acid signaling, tryptophan–kynurenine–serotonin metabolism, vagal communication, and regulation of the hypothalamic–pituitary–adrenal axis. Food matrix studies support the potential application of postbiotics in fermented dairy products, cereal-based systems, plant-based matrices, powders, concentrates, and bioactive packaging; however, matrix-dependent effects on bioavailability, sensory quality, and biological activity remain incompletely defined. Postbiotics provide a stable translational platform for functional-food development, but their scientific and commercial use requires clear characterization of the microbial source, production process, inactivation method, retained active fractions, dose metric, delivery matrix, and clinically meaningful endpoint. Future studies should avoid broad category-level claims and prioritize preparation- and matrix-defined human evidence with standardized safety reporting.
Elmas et al. (Fri,) studied this question.