Simulating the biochemical environment for infant intestinal digestion: key challenges and recommendations

Digestion in the small intestine is a crucial step in the breakdown and absorption of nutrients from human milk. In vitro models of intestinal digestion are commonly employed to investigate the digestion behaviour of breast milk nutrients. Accurate replication of the infant small intestine requires a detailed understanding of its biochemical environment. This review summarises current knowledge on small intestinal digestion in infants, integrating evidence from both human studies and in vitro intestinal digestion models. Key challenges in simulating the infant small intestinal conditions, including motility, intestinal fluid dynamics and composition, enzymatic activity, and absorption are discussed. This literature review also provides recommendations for enhancing the physiological relevance of in vitro small intestinal digestion systems for studying intestinal digestion in early infancy.