Dietary Patterns, Foods and Fiber in Irritable Bowel Syndrome and Diverticular Disease

Abstract

Irritable bowel syndrome (IBS) is the most common gastrointestinal disorder occurring in people <45 years. Diverticular disease is among the most clinically and economically significant gastroenterological conditions in people ≥65 years of age. Having a history of IBS appears to increase the risk of diverticular disease in older age. IBS, previously called colitis, does not generally show visible structural or anatomic abnormalities, but is characterized by abdominal pain, bloating, distension, and changes in bowel habits. Celiac disease may be confounding and difficult to distinguish from IBS symptoms. Diverticular disease may evolve from colonic diverticulae (herniate pouches) potentially caused by high colonic intraluminal pressure which occurs in most people with aging but only approximately 20% of individuals with diverticulae develop abdominal symptoms (symptomatic uncomplicated diverticular disease). A smaller percentage of older individuals eventually develop complications such as severe bouts of diverticulitis or bleeding that may lead to sepsis and death. Healthy dietary patterns and low intake of fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAPs) may help to lower the risk and alleviate symptoms associated with IBS and diverticular disease. For IBS, psyllium is the fiber source most consistently found to help provide moderate relief of symptoms. For uncomplicated diverticular disease, fiber-rich healthy diets and low red or processed meat consumption decrease the risk, and fiber-rich diets, and foods or supplements containing wheat bran, psyllium or methylcellulose may help to alleviate diverticular disease symptoms and/or improve bowel function. Fiber related mechanisms that may help reduce risk or manage symptoms of IBS or uncomplicated diverticular disease are related to: (1) improved colonic health by promoting better laxation and stool bulk, and a healthier microbiota ecosystem with higher fecal ratio of probiotic to pathogenic bacteria and higher butyrate concentrations associated with lower colonic inflammation and improved colonocyte structure and function; and (2) reduced risk or rate of annual body weight and central abdominal fat gains (or promotion of a gradual lowering of body weight and waist size in overweight or obese individuals).