Abstract
Undernutrition affects thousands of children under five years old worldwide, and various factors are related to its onset, among which we highlight enteric infections and gastrointestinal barrier dysfunction. The cycle of intestinal infections and undernutrition has long-term consequences, such as cognitive deficits, poor growth, and metabolic diseases in adulthood. This review explores factors linked to childhood undernutrition, focusing on intestinal infections and markers of intestinal permeability that affect child development. This narrative review was conducted using Medline/PubMed, Web of Science, and Scopus, from July 2024 to March 2025. Studies involving children under five years old and addressing undernutrition, intestinal infections, or intestinal permeability markers were included. Exclusion criteria comprised studies without therapeutic focus, and books, case reports, or academic theses. No language restrictions were applied, and registration on global platforms was not required. Overall, the studies reported a close relationship between enteric pathogens, diarrheal and non-diarrheal stools, and undernutrition. Among the pathogens most frequently found in the feces of malnourished children were Shigella, enterotoxigenic Escherichia coli, enteroaggregative E. coli (EAEC), and Cryptosporidium. The studies also showed the relationship between gastrointestinal barrier function and undernutrition, with the deterioration of nutrient absorption and, consequently, repercussions on development, linear growth, and weight in children. Although the studies analyzed had different designs and heterogeneity in the age range of the studied children, it was possible to observe the relationship between the infection/undernutrition cycle. Future studies should optimize personalized nutrient-based therapies, assess long-term effects on gut health and growth, and explore the gut microbiome's role in enteric infection susceptibility and undernutrition.