ABSTRACT
This chapter considers epidemiology data, genetics and immunology and the microbiota to attempt to understand the factors leading to Inflammatory Bowel Disease (IBD). Sunlight accounts for 80% of vitamin D in the human body, and vitamin D deficiency is one explanation for the north-south gradient21 in the incidence of IBD. Patients generally assume that a gut disorder, such as IBD, must be linked with diet, but this has proved extremely difficult to show. Mycobacterium Avium Subs. Paratuberculosis (MAP) causes chronic inflammation in several mammalian species, and is an obligate intracellular mycobacterium. MAP is detectable in Crohn’s-affected tissues, but it is difficult to prove that MAP infection preceded the gut damage. The importance of genetics in the aetiology of IBD is evident from twin studies showing higher risk in monozygotic than dizygotic twins. Epithelial barrier integrity is crucial for intestinal homeostasis in the context of IBD.
