Plant-Derived Protein Hydrolysates and Bioactive Peptides for Restoring Gut Health in Undernutrition: A Scoping Review of Intestinal Barrier Protection, Inflammatory Signaling, and Oxidative Stress Regulation

Background: Childhood undernutrition is associated with intestinal barrier dysfunction, gut dysbiosis, and increased susceptibility to gastrointestinal complications. This review examines whether plant-derived protein hydrolysates and bioactive peptides can influence gut barrier integrity, inflammatory signaling, oxidative stress, nutrient absorption, and microbiota composition. Methods: A scoping review of evidence published from 2010 and 2026 was conducted following a structured, multi-database search and screening process. Studies were assigned to defined evidence categories according to whether the intervention was an identified peptide sequence, a peptide fraction, a whole hydrolysate, an intact protein, or a complex food matrix. Results: Plant-derived protein hydrolysates, peptide fractions, and identified peptides were reported to increase occludin, claudin-1, and ZO-1 expression and reduce epithelial permeability in colitis models and in human-derived intestinal monolayers. Several interventions inhibited NF-κB and MAPK signaling, reducing TNF-α, IL-6, and IL-1β. Selected interventions lowered intestinal malondialdehyde and raised superoxide dismutase, glutathione peroxidase, and total antioxidant capacity; three studies demonstrated Keap1–Nrf2–ARE pathway activation directly. Microbiota effects were compositional, with increased short-chain fatty acid production, higher abundances of Lactobacillus and Bifidobacterium, and reduced pathobionts. Evidence for nutrient absorption was weaker: no included study measured PEPT1 expression, transport activity, or peptide flux following hydrolysate administration, and most sequences reviewed exceeded the di- and tripeptide substrate limit of that transporter. Conclusions: No included study administered a plant-derived peptide in a model of undernutrition, and none assessed clinically diagnosed SIBO. Mechanistic evidence suggests plausible benefits for gut barrier integrity, redox balance, inflammation, and microbiota composition, but controlled trials in undernourished children are required before clinical claims can be made.