Background: Breath testing for food intolerances is becoming routine in patients with functional gastrointestinal disorders (FGID). Both FGID and saccharide intolerances (FODMAPs: fermentable oligo-, di-, polysaccharide and polyols, e.g. lactose, fructose, sorbitol) are common (>10% of any given population) and often respond to dietary modification. The breath tests are based on quantification of gas excretion in breath as a sign of malabsorption and symptom provocation, but are likely subject to considerable psychological bias. The role of expectation and other psychological effects on breath testing has not been reported, but is crucial for the validation of these increasingly wide-spread tests with considerable dietary and potentially deleterious consequences. Fructose has been shown to result in short term pro-inflammatory metabolic responses, but these effects have not been studied as underlying causes for intolerance symptoms in fructose intolerant patients with FGID.

Aim: To investigate the psychological component and the short-term metabolic effects of fructose breath testing in patients referred for evaluation of FGID using placebo. Additionally, to assess baseline predictors for a positive breath test result.

Methods: Fructose intolerance (defined by a positive symptom index) and malabsorption (defined by increased breath hydrogen/methane concentrations) will be determined in 30 successive male and female FGID in a single centre using breath-testing. Fructose 35g, given double-blind as well as open, a sweet placebo (cyclamate/saccharine; Assugrin®) and a neutral (still water) placebo given double-blind will be compared in a randomized, cross-over sequence and according to our standardised procedure on four separate study days. Symptoms will be recorded using standardised questionnaires and breath concentrations of H2 and CH4 will be measured during testing on the four study days. Somatisation and psychological profiles will be assessed by questionnaires. Blood samples will be obtained before and during provocation testing to assess short-term responses to fructose loading by metabolomics. Fructose, blinded and open, and placebo responses will be compared and baseline predictors for a positive breath tests assessed.

Inclusion criteria

• Thirty male or female FGID (Irritable Bowel Syndrome or Functional Dyspepsia according to the Rome III criteria) patients -
• 10 healthy female and male controls
• aged between 18 and 60 years

Exclusion criteria:

• Bowel resections, except appendicectomy or cholecystectomy
• Evidence of organic disease
• No medications (excluding antihypertensives, antidepressants and low-dose aspirin), including herbal, from 4 days before the first study day until after breath test
• Coeliac's disease