The aim of this study performed in Irritable Bowel Syndrome (IBS) subjects and healthy patients is to demonstrate the ability of composite score of frequency of gastrointestinal symptoms to discriminate healthy subjects and IBS patients. The properties of this questionnaire of composite score of gastrointestinal symptoms frequency will be compared to other validated questionnaires (severity of IBS symptoms and HRQoL).

Inclusion Criteria:

• for Healthy subjects :
• Healthy women and men free-living subject aged from 18 to 65 years.
• Subject with a body mass index between 18 and 30, bounds included.
• Subject having given written consent to take part in the study.
• Chronic medical treatment-free excluding contraceptive and stable Hormonal Replacement Therapy
• for IBS Patients :
• IBS women and men free-living subject aged from 18 to 65 years
• Subject with a diagnosis of IBS according to Rome III criteria: recurrent abdominal pain or discomfort at least 3 days per month in the last 3 months associated with 2 or more of the following: improvement with defecation; onset associated with a change in frequency of stool; onset associated with a change in form (appearance) of stool.
• Subject with a diagnosis of IBS according to Rome III criteria with symptom onset at least 6 months prior to diagnosis.
• Subject having an IBS-SSS score higher or equal to 75 corresponding to an active phase of IBS symptoms.
• Subject having given written consent to take part in the study.

Exclusion Criteria:

• for Healthy subjects :
• Subject who, in the past, has consulted a general practitioner or a gastroenterologist for (IBS) or any other functional bowel disease including constipation and diarrhoea.
• Subject with known organic disease, including an inflammatory bowel disease, a benign or malign tumour of intestine or colon and significant systemic disease
• Subject treated with any chronic medical treatment that, in the investigator's opinion could interfere with the GI tract.
• Subject who underwent general anaesthesia in the preceding 4 weeks.
• Pregnant subject or breast-feeding subject at the time of the study.
• Subject with known immunosuppression
• Subject with any known food allergy
• Subject involved in any other clinical study within the preceding month or in exclusion period after another clinical study.
• Subject in a situation, which in the investigator's opinion could interfere with optimal participation in the present study or could constitute a special risk for the subject.
• Subject not able to read, to understand and/or to answer to the questionnaires.
• for IBS Patients :
• If a subject fulfils with one of the following criteria, he/she must be excluded from the study:
• Subject with a diagnosis of IBS with clinical signs of alarm (rectorragy, fever, associated inflammatory articular signs, recent weight loss).
• Subject with known organic disease, including an inflammatory bowel disease, a benign or malign tumour of intestine or colon and significant systemic disease.
• Subject who underwent general anaesthesia in the preceding 4 weeks.
• Pregnant subject or breast-feeding subject at the time of the study.
• Subject involved in any other clinical study within the preceding month or in exclusion period after another clinical study.
• Taking antidepressant or analgesic drugs.
• Subject not able to read, to understand and/or to answer to the questionnaires.

Adult healthy subjects and adult IBS patients (Rome III criteria, all subtype)