Nutrients and Gut Health

production of proinflammatory cytokines [6, 7] . In addition, the production of antimicrobial bacteriocins can be decreased [8] . The intestinal barrier is a functional unit including the epithelial cells, mucus and different secreted substances such as defensins, lysozymes and immunoglobulins (e.g. IgA). These components are important to control the microbial composition in the gut. IgA can bind bacteria and viruses, and the defensins have direct antimicrobial activities against bacteria [9–11] . The innate and acquired intestinal immune systems are able to differentiate between the beneficial and harmful bacteria and are therefore essential for the immune homeostasis in the gut. There is constant crosstalk between the intestinal bacteria and the innate immune system. The information is transmitted through specific pattern-recognition receptors (e.g. NODand Toll-like receptors) [12] . Patients with IBD have a loss of tolerance to their own intestinal bacteria. It is known that patients with IBD have a decreased number of beneficial bacteria and an increased number of pathogenic bacteria adherent to the mucosa and within the epithelium [2] . It appears that these bacteria trigger a strong mucosal immunological response leading to inflammation and intestinal epithelial cell injury, mediated by activated T cells, mononucleInflammatory bowel diseases (IBD), such as ulcerative colitis, pouchitis and Crohn’s disease, are chronic inflammatory disorders caused by increased oxidative and metabolic stress. In the last decade, an increase of the incidence rates in different areas of the world has been reported. This also happened in countries (particularly in Asia) where IBD was previously uncommon. It is unclear if the rise of the incidence in this part of the world is due to improved diagnosis methods or environmental triggers. The exact etiology of IBD is still not clear, but it seems that a genetic predisposition, an exaggerated immune response to environmental triggers (e.g. nutritional components, infections) and the composition of the intestinal bacteria are involved [1, 2] . None of these alone is sufficient or essential to cause the typical intestinal lesions. In the gut, bacteria, the intestinal barrier and the intestinal immune system are a close entity. It is well known from experimental models that without intestinal bacteria no IBD can develop [3, 4] . The composition of the different bacteria is very important [5] . A reduction of the commensal lactobacilli and bifidobacteria can lead to decreased fermentation of unabsorbed carbohydrates with less production of short-chain fatty acids. Butyrate is an important source of energy for the epithelial cells and is able to downregulate inflammation by decreasing the Published online: April 14, 2011