Curcumin: A Comprehensive Review of Its Bioactivities, Therapeutic Potential, and Safety in Functional Food and Health Applications

Curcumin, the principal polyphenol derived from <em>Curcuma longa</em>, has evolved from a traditional culinary pigment to a promising functional-food ingredient with extensive physiological applications. This review synthesizes six decades of research elucidating this transformation. Initially, we summarize curcumin’s ethnomedical origins, followed by an analysis of its pharmacokinetic profiles in rodents and humans. Native curcumin predominantly resides within the intestinal lumen and mucosa; however, contemporary delivery systems—including solid-lipid nanoparticles, micelles, protein–polysaccharide complexes, and piperine co-crystals—can significantly enhance systemic bioavailability by up to two orders of magnitude. We subsequently examine mechanistic evidence across nine major health domains, highlighting cardiovascular, neuroprotective, respiratory, gastrointestinal, anti-tumor, and metabolic effects, supported by more than 250 primary studies published between 2020 and 2024. Animal toxicology and clinical safety data confirm a wide safety margin, supporting the currently established acceptable daily intake of 0–3 mg kg^-1 body weight. Nonetheless, potential interactions with anticoagulants and hormetic pro-oxidant effects observed at very high doses merit continued monitoring. Ongoing challenges encompass dose standardization, metabolite characterization, and precision-nutrition clinical trials stratified by microbiome and genetic factors. Addressing these research gaps and integrating curcumin into optimized food matrices are essential steps toward translating laboratory findings into evidence-based dietary strategies that safely enhance human health.