This review highlights the importance of intestinal permeability and the intestinal barrier in health and disease. The intestinal barrier, a complex structure composed of physical and functional components, plays a crucial role in protecting the body from microbial invasion and toxins while allowing essential nutrients to be absorbed. Intestinal permeability, which is closely linked to the intestinal microbiota and mucosal immune system, can be influenced by various factors such as diet, gut microbiota, and lifestyle. Disruption of the intestinal barrier can lead to a range of diseases, including critical illness, inflammatory bowel diseases, celiac disease, food allergies, irritable bowel syndrome, obesity, and metabolic disorders. The review discusses the definition and assessment of intestinal permeability, the key elements affecting it, and the regulatory mechanisms involved. It also explores the clinical significance of intestinal permeability and the potential role of prebiotics, probiotics, and dietary factors in modulating it. Finally, the review outlines various methods for assessing intestinal permeability, including the Ussing chamber, permeability assays, and biomarker measurements, and highlights the challenges and limitations of these approaches.This review highlights the importance of intestinal permeability and the intestinal barrier in health and disease. The intestinal barrier, a complex structure composed of physical and functional components, plays a crucial role in protecting the body from microbial invasion and toxins while allowing essential nutrients to be absorbed. Intestinal permeability, which is closely linked to the intestinal microbiota and mucosal immune system, can be influenced by various factors such as diet, gut microbiota, and lifestyle. Disruption of the intestinal barrier can lead to a range of diseases, including critical illness, inflammatory bowel diseases, celiac disease, food allergies, irritable bowel syndrome, obesity, and metabolic disorders. The review discusses the definition and assessment of intestinal permeability, the key elements affecting it, and the regulatory mechanisms involved. It also explores the clinical significance of intestinal permeability and the potential role of prebiotics, probiotics, and dietary factors in modulating it. Finally, the review outlines various methods for assessing intestinal permeability, including the Ussing chamber, permeability assays, and biomarker measurements, and highlights the challenges and limitations of these approaches.