Patients with irritable bowel syndrome (IBS) often benefit from dietary changes. The effect of a gluten-free diet (GFD) on clinical symptom improvement and psychological well-being will be checked in patients with IBS. In addition, the stimulatory potential of gluten on peripheral blood monocytes will be determined. Responders will be provoked with gluten containing bars or placebo bars to confirm the diagnosis of non-celiac glutensenstitivity.

Patients with irritable bowel syndrome (IBS) often benefit from dietary changes. Since it has been shown that a gluten free diet (GFD) often alleviates the clinical symptoms, an overlap between patients with IBS and non-celiac glutensensitivity is assumed. The study includes 25 healthy individuals and 150 patients with IBS taking a six week GFD. Participants fill in questionnaires to determine clinical symptoms and psychological well being at the beginning and end of the dietary intervention. Patients with symptom relief under diet are further provoked in a double-blind placebo-controlled study with gluten or placebo containing bars for three weeks, separated by two weeks of washout to diagnosis of NCGS.

In addition, peripheral mononuclear cells are isolated at the beginning and end of the diet and the stimulating potential of wheat gluten is analyzed.

Inclusion Criteria:

• healthy controls without gastrointestinal Symptoms
• patients with irritable bowel Syndrome (Rome IV criteria)

Exclusion Criteria:

• inflammatory bowel disease (Crohn's disease, Ulcerative colitis)
• celiac disease
• wheat allergy
• pregnancy