Non-allergic gluten sensitivity. A controversial disease - or not yet sufficiently explored?

The avoidance of wheat, gluten and other cereal products is a growing phenomenon in industrialized countries. The diagnostic criteria of celiac disease and of food allergy to wheat flour and/or other cereals are clearly defined. Only about 0.5-25 % of the population are affected from both of these immunological diseases. Nevertheless, there exists a significantly greater proportion of people reporting at least subjectively significant complaints and quality of life improvements after switching to a wheat- or gluten-free diet. Celiac disease or wheat allergy cannot be detected in these individuals on the basis of established criteria. The absence of clear diagnostic autoimmune or allergic criteria in these wheat sensitive patients has resulted in the description of non-celiac gluten sensitivity. It is clinically detectable in only very few individuals and may manifest with either intestinal, extra-intestinal or neurovegetative and psychosomatic symptoms, respectively. However, non-celiac disease gluten sensitivity has to be differentiated critically from irritable bowel syndrome, carbohydrate malassimilation, postinfectious conditions and psychosomatic diseases. Pathophysiologically, non-celiac disease gluten sensitivity is still poorly characterized; several non-immunological mechanisms are discussed to contribute to non-celiac gluten sensitivity. These include the effects of fructo- and galacto-oligosaccharides, of trypsin inhibitors of amylase, and wheat lectin agglutinins, which may influence or modulate intestinal permeability and/or a non-specific immune or effector cell degranulation within the gastrointestinal tract. In addition, further metabolic effects with direct or indirect influence on the intestinal flora are currently discussed. In addition to subjectively reported changes in symptoms that may affect variably intestinal, as well as extra-intestinal and/or neuropsychiatric symptoms, some studies suggest that there is little reproducibility of complaints from gluten exposure. For a definitive diagnosis of non-celiac gluten sensitivity, structured (blinded) challenge tests with wheat or gluten are mandatory as well as re-challenge after a defined time of gluten avoidance to establish non-celiac disease gluten sensitivity as a persistent disease entity.