Background: Different food items are made responsible for irritable bowel syndrome (IBS) symptoms, but the physiopathology of IBS remains unclear. Aims: During a meeting in Nice, France, experts of the European Working Team of the IBiS Club discussed selected data regarding the relationships between alimentation, food items (including fibers) and IBS symptoms. Methods/Results: Food allergy remains a difficult diagnosis, but medical and general history, presence of general symptoms such as skin rash, and hypersensitivity tests may help in achieving a positive diagnosis. On the other hand, food intolerance is more confusing because of the subjectivity of the relationship between ingestion of certain foods and the appearance of clinical symptoms. Different food items which are commonly implicated in adverse reactions mimicking IBS were found to be stimulants for the gut, suggesting that patients with predominant diarrhea IBS have to be carefully questioned about consumption of different kinds of food (i.e., coffee, alcohol, chewing gum, soft drinks) and not only on lactose ingestion. Gas production is discussed on the basis of retention of intestinal gas as well as on malabsorption of fermentable substrates. The role of a large amount of this kind of substrate reaching the colon is suggested as a potential mechanism of IBS-type symptoms in overeating patients. Regarding the role of fiber in IBS, the expert group concluded that fibers are not inert substances and that they could trigger pain or bloating in some IBS patients. Conclusion: Despite numerous reviews on this subject, it is very difficult to give general dietary advice to IBS patients, but dieteticians may have a positive role in managing such patients.