Non Celiac Gluten Sensitivity (NCGS) is an emergent syndrome mainly inducing gastrointestinal symptoms. NCGS is suspected to be present in the 6% of the population and thus it represents an important issue in health care. Actually it remains difficult to diagnose and prove due to the lack of established criteria. The investigators intention is to establish a diagnostic flowchart to evaluate the real impact of NCGS in a cohort of patients suffering from functional gastrointestinal symptoms.

The proposed study has been designed to be a randomised double-blind multicenter clinical trial with crossover. The Coordinating Center will be the "Centro per la Prevenzione e la Diagnosi della Malattia Celiaca", Fondazione IRCCS Ca' Granda - Ospedale Maggiore Policlinico, Milano. Secondary enrollment centers will be Italian Gastroenterology Units with outpatient services. Enrollment criteria will be diagnosis of irritable bowel syndrome (IBS) or functional dyspepsia. Patients with other functional gastrointestinal disorders will be included in the group "Functional non specific gastrointestinal symptoms".

After they give their written informed consent, patients will undergo the diagnostic work-up recommended in case of suspected irritable bowel symptoms/functional dyspepsia and aimed at the exclusion of CD or allergy to alimentary antigens by means of serological testing (anti transglutaminase antibodies) or skin tests, or other gastrointestinal diseases. Endoscopic, histologic and/or imaging exams together with supplemental blood tests will be prescribed on individual cases and according with the international guidelines.

Enrolled subjects will be asked to fill

• a checklist for the evaluation of the psychological profile (SCL90 questionnaire, with the particular aim of evaluating levels of anxiety, depression and somatisation);
• a questionnaire about the perceived level of physical and mental health (SF36 questionnaire);
• Ten centimeters long visual analogue scales (VAS) on the level of satisfaction with their health status and on the intensity of the single symptoms.

At the end of the present phase patients will start a GFD for the subsequent three weeks.

At the end of the GFD period patients will fill VAS and SF36. Only those patients presenting a 30% increase of the global VAS score ("GFD Responders") will continue the study. Conversely, non responders will be considered "non gluten sensitive" and they will finish the trial.

Responders to the GFD period will entry the randomisation phase and will undergo a double-blind stimulation test with cross over. Patients will be randomised to assume gluten or placebo for 7 days. After the treatment patients will fill VAS and SF36.

A diagnosis of NCGS will be ascertained in case of symptomatic response limited to gluten ingestion.

Inclusion Criteria:

• Subjects with gastrointestinal functional disorders (irritable bowel syndrome, functional dyspepsia or unspecified functional gastrointestinal symptoms)

Exclusion Criteria:

• Celiac disease
• Alimentary allergies
• Inflammatory bowel disease
• Major abdominal surgery
• Psychiatric disorders
• Neoplasia