Colorectal disorders: A dietary management perspective

Dietary lifestyle is relevant for prevention and treatment of various colorectal conditions. Colorectal disorders have significant morbidity and mortality in a western-style community, particularly irritable bowel syndrome (IBS), colorectal cancer, haemorrhoids, constipation and diverticular disease. This review addresses how bowel health can be maintained, what foods and dietary lifestyles are associated with risk for disease and what foods are of real value in management. Bowel health is that state where the individual is satisfied with defaecation, the diet does not create undue risk for disease and lumenal contents maintain an intact and functional mucosa. Bowel health depends on a healthy dietary lifestyle, but in particular on an adequate intake of non-digestable dietary polysaccharide. Diet influences biology in part by altering the lumenal environment. Effects such as high butyrate levels, lowered pH, a predominance of 'healthy'over 'unhealthy' bacteria, rapid intestinal transit, high faecal bulk, a non-leaky epithelial barrier, adsorption of dietary carcinogens by fibre, low bile salt concentrations, reduced generation of toxic bile salts or protein derivatives and provision of certain bioactive substances are seen as beneficial. Diet influences future risk for colorectal cancer (vegetables, animal fats, polysaccharides amongst others) and for diverticular disease (fibre). Adequate fibre and resistant starch can improve constipation and anorectal conditions such as fissure and haemorrhoids. The role of diet in managing patients with IBS is complex. Fibre may worsen symptoms in severe cases of IBS, diverticular disease and inflammatory bowel disease. Certain carbohydrates of limited digestibility/absorbability, such as lactose, fructose and sorbitol, can precipitate IBS symptoms. Low fat, high fibre diets may reduce recurrence of colorectal adenomas. Diet has a significant role to play in colorectal disorders.