The etiology of Crohn's disease and ulcerative colitis has been elusive, and questions regarding the pathogenesis of the disease have led to many proposals, including some related to diet. Over the years there have been theories that a cow's milk allergy was an underlying factor in these diseases. Other related proposals have implicated lack of breast feeding. High sugar consumption and lack of dietary fiber have been suggested to be associated with the occurrence of IBD .
It has been proposed that in genetically susceptible individuals exposure to various environmental factors may cause an upregulation of immunological response that could result in IBD . Gassull and Cabré suggest that changes in lifestyle, including dietary changes that have resulted from economic well being in the western world may be responsible for the increasing incidence of IBD . They propose that exposure of the intestinal lumen to specific nutrients may act as an antigenic agent or possibly as a moderator of regulatory mechanisms of the mucosal cells, potentially leading to IBD.
Short chain fatty acids have long been recognized to be the preferred fuel for colonocytes. Butyrate, a four-carbon saturated fatty acid, is the most abundant of the short chain fatty acids in the intestinal lumen, as it is the main product of bacterial fermentation of unabsorbed carbohydrate, primarily dietary fiber. Segain et al. found that butyrate has an anti-inflammatory effect, decreasing the TNFa production, cytokine messenger RNA expression and production of nuclear factor kB in tissue cultures derived from colonic biopsies of patients with Crohn's colitis . The final mediator was proposed to be nuclear factor kB, the regulator of transcription of cytokine genes, including that of TNFa. This raises the question of whether a decreased intake of dietary fiber could have a role in the etiology of IBD, particularly in colonic disease.
Dietary fat as a putative etiologic agent has been implicated in part based on the observed lower incidence of inflammatory diseases in the Eskimos of Greenland . This population group has a very high intake of fish, thus of omega-3 fatty acids , which have anti-inflammatory effects [24, 25]. Geerling and coworkers published case-control studies that found an association between high intakes of monounsaturated fats, omega-6 fatty acids and vitamin B6and increased incidence of developing ulcerative colitis .
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