Bioactive Peptides Derived from Goat Milk: A Critical Narrative Review of Generation Pathways, Evidence Quality and Translational Barriers

Abstract

Goat milk is consumed widely across Asia, Africa and the Mediterranean basin and is frequently promoted as a source of health-promoting protein fragments. Research on peptides released from caprine caseins and whey proteins has expanded rapidly, yet much of the literature reports promising laboratory activities without establishing whether those activities survive digestion, reach physiologically relevant sites or alter health outcomes in people. This critical narrative review examined the peer-reviewed literature on bioactive peptides generated from goat milk proteins through enzymatic hydrolysis, microbial fermentation, cheese ripening and gastrointestinal digestion. Literature was identified through structured searches of multidisciplinary, agricultural and biomedical scholarly indexes, supplemented by citation searching, and was appraised according to study design, analytical rigour and physiological relevance rather than by publication volume. The synthesis was organised around five themes: the compositional and genetic basis of caprine peptide precursors; the routes by which peptides are generated; the evidence for specific activities, including inhibition of angiotensin I-converting enzyme, antioxidant, antimicrobial, glucoregulatory and lipid-modulating effects; the stability and bioavailability of peptides after ingestion; and the methodological and regulatory barriers to translation. Evidence was strongest for the release of peptides with blood pressure-related enzyme inhibitory activity during standardised laboratory digestion and fermentation, supported by a small number of animal studies. Evidence for antioxidant, antimicrobial, glucoregulatory, anti-inflammatory and anticancer effects rested predominantly on chemical assays, cell models and computational prediction. Human evidence specific to goat milk was limited to a few small, short trials with inconsistent results, and inferences frequently depended on extrapolation from bovine milk peptides whose clinical effects remain contested. Recurrent weaknesses included non-standardised enzyme assays, reliance on non-human digestive enzymes, uncertain peptide identification, limited dose realism and uneven geographical representation. Genetic polymorphism at caprine casein loci is a plausible but largely untested source of variation in peptide yield. The field now requires genotype-resolved and quantitative peptidomics, human-relevant digestion and absorption studies, and adequately powered controlled trials with clinically meaningful end points. Goat milk proteins are a credible source of candidate bioactive peptides, but claims of demonstrated health benefit are not yet justified by the available evidence.