[Current issues on irritable bowel syndrome: diet and irritable bowel syndrome]

Irritable bowel syndrome (IBS) is one of the most prevalent functional gastrointestinal disorders. It is a multifactorial disorder with its pathogenesis attributed to abnormal gastrointestinal motility, low-grade inflammation, visceral hypersensitivity, communication in the gut-brain axis, and so on. Traditionally, IBS has been treated with diet and lifestyle modification, fiber supplementation, psychological therapy, and pharmacological treatment. Carbohydrates are intermingled with a wide range of regularly consumed food including grains such as rye and wheat, vegetables, fruits, and legumes. Short-chain carbohydrates that are poorly absorbed exert osmotic effects in the intestinal lumen increasing its water volume, and are rapidly fermented by bacteria with consequent gas production. These effects may be the basis for the induction of most of the gastrointestinal symptoms. This has led to the use of lactose-free diets in those with lactose intolerance and of fructose-reduced diets for fructose malabsorption. As all poorly absorbed short-chain carbohydrates have similar and additive effects in the intestine, a concept has been developed to regard them collectively as FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides and polyols) and to evaluate a dietary approach that restricts them all. Based on the observational and comparative studies, and randomized-controlled trials, FODMAPs have been shown to trigger gastrointestinal symptoms in patients with IBS. Food choice via the low FODMAPs and potentially other dietary strategies is now a realistic and efficacious therapeutic approach for managing symptoms of IBS.