Development of the Gastrointestinal Tract and Microbiome in Early Childhood: Anatomical, Physiological, and Ecological Perspectives

The first five years of life are a period of rapid and coordinated transformation of the gastrointestinal (GI) tract, spanning anatomical expansion, physiological specialization, and ecological succession of the gut microbiome. These changes are coupled to dietary transitions, from exclusive milk feeding to mixed and solid food intake, and are foundational to host metabolic programming, immune education, and long-term health trajectories. In this summary, I will review the dynamics of the GI maturation focusing on the microbiome and give examples of how food and nutrition impact or influence these processes.