Hen Egg-Derived Bioactive Proteins and Peptides at the Gut Interface: From Molecular Characterization and Digestion to Microbiome Interactions and Prospective Precision Nutrition

Hen eggs (Gallus gallus domesticus) contain bioactive proteins, peptides and lipids, but compound characterization, mechanistic cell and animal studies, and human consumption trials have developed largely in isolation. This narrative review, supported by a documented literature search, follows one pathway: egg composition, molecular characterization, processing and digestion, bioaccessibility, intestinal and microbial interaction, host signaling, and a prospective precision-nutrition outlook. Findings are classified into translational evidence categories (a heuristic classification of experimental systems, not a ranking of study quality) and summarized in a multidimensional evidence matrix. Egg white and yolk proteins, including ovotransferrin, ovomucin and lysozyme, yield characterized peptides, notably the ovotransferrin tripeptides IRW (Ile-Arg-Trp), IQW (Ile-Gln-Trp) and LKP (Leu-Lys-Pro), and ovomucin hydrolysates, whose activities in cell and animal models are compound-specific: LKP, for example, did not reproduce the effect of IRW on insulin resistance in muscle cells. In humans, one small ileostomy study (n = 5) reports higher ileal protein digestibility for cooked than raw egg, short-term trials show that whole-egg intake raises plasma choline, and an antibiotic-suppression study shows that trimethylamine-N-oxide formation after eggs plus phosphatidylcholine depends on gut microbiota. No study identified shows that IRW, IQW or LKP are generated, survive digestion or reach the circulation after ordinary egg consumption, and only six human studies address egg intake and the gut microbiome. Dose–response, delivery-system and safety data are largely missing, and precision nutrition for egg bioactives remains a research framework. Priorities are human pharmacokinetic confirmation, longer trials with shotgun metagenomics and functional readouts, and independent safety testing.