This study objective is to assess the short and long term effects of partially hydrolyzed guar gum (PHGG) administration on clinical symptoms of IBS and quality of life of these patients.

Inclusion Criteria:

• Fulfillment of the Rome III criteria for IBS.
• Aged 20-68 years at the time of screening.
• Provision of written informed consent.
• Commitment of availability throughout the 6 months study period.

Exclusion Criteria:

• Major abdominal surgery in the past.
• The presence of any active (organic)GI disease.
• Past or present major medical or psychiatric illness.
• Any concomitant disease.
• Alarming symptoms (rectal bleeding, weight loss, etc.)
• Pregnancy.
• Family history of colorectal carcinoma or inflammatory bowel disease (IBD).
• Abnormal laboratory studies (blood biochemistry , liver enzymes,complete blood count), abnormal thyroid function.
• Non-adjusted diet in the case of lactose or gluten intolerance.
• Recent travel to regions with endemic parasitic diseases.