Treatment of IBS is very problematic. Despite the wide range of pharmacological and non-pharmacological therapies, there is no universally accepted approach. In recent years, the low FODMAP diet has been developed, a dietary approach that aims to relieve the symptoms of IBS. FODMAPs (Fermentable Oligosaccharides, Di-saccharides, Mono-saccharides and Polyols) are a group of dietary sugars that may be poorly absorbed in the small intestine and fermented by bacteria to produce gas. Ingestion of FODMAPs may also result in alterations in fluid content in the colon and trigger functional gut symptoms in some individuals. This study aims to examine the effectiveness of the FODMAP diet in Israel in improving symptoms of IBS compared to the standard dietary advice.

Inclusion Criteria:

1. Fulfillment of the Rome III criteria for IBS.
2. Aged 18-77 years at the time of screening.
3. Provision of written informed consent.
4. Commitment of availability throughout the 10 week study period.
5. Availability of at least one GI imaging study during the last 5 years (colonoscopy, sigmoidosopy, abdominal ultrasonography, barium enema) for subjects older than 50 years.

Exclusion Criteria:

1. Major abdominal surgery in the past.
2. The presence of any active (organic) GI disease.
3. Past or present major medical or psychiatric illness.
4. Any concomitant disease.
5. Alarming symptoms (rectal bleeding, weight loss, etc.)
6. Pregnancy.
7. Family history of colorectal carcinoma or IBD, under the age of 50.
8. Abnormal laboratory studies (blood biochemistry, liver enzymes, complete blood count), abnormal thyroid function.
9. Non-adjusted diet in the case of lactose or gluten intolerance.
10. Recent travel to regions with endemic parasitic diseases.