Background: The association of fructose and lactose intolerance and malabsorption with the symptoms of different functional gastrointestinal disorders (FGID) is unclear. The mechanisms behind the multi-organ symptoms remain unclear. Both FGID and saccharide intolerances are common (>10% of any given population). Dietary modification based on intolerance diagnostics could provide an effective treatment for FGID, which are otherwise difficult to treat.

Aim: To investigate the prevalence and interrelationships of fructose and lactose intolerance (symptom induction) and malabsorption (breath test gas production) and their association with clinical GI as well as non-GI symptoms in FGID and the outcome of standard dietary intervention. Mechanisms related to symptom genesis will be investigated using metabolomic analysis of plasma and urine by gas chromatography/time-of-flight mass spectrometry (GC/TOFMS).

Methods: Fructose and lactose intolerance (defined by positive symptom index) and malabsorption (defined by increased hydrogen/methane) will be determined in successive male and female FGID patients in a single center using breath-testing. Symptoms will be recorded using standardised questionnaires and the Rome III criteria. The prevalence of the intolerances in the different FGID subgroups and the associations between breath testing results, clinical symptoms and the outcome of dietary modification will be assessed. Factors predictive of the outcome of dietary modulation will be screened for. GC/TOFMS will be used to assess the human and microbial metabolome in urine and plasma.

Inclusion criteria:

• Patients with functional GI disorders according to ROME 3 criteria
• Without evidence of organic disease by standardised testing in GI practice.

Exclusion criteria:

• Current or relevant history of organic disease.

Successive patients referred to our gastroenterology practice with functional GI disorders according to ROME 3 criteria.