Fructose and Lactose Intolerance and Malabsorption Testing

The Relationship With Symptoms in Functional Gastrointestinal Disorders

C. H. Wilder-Smith; A. Materna; C. Wermelinger; J. Schuler


Aliment Pharmacol Ther. 2013;37(11):1074-1083. 

In This Article

Abstract and Introduction


Background The association of fructose and lactose intolerance and malabsorption with the symptoms of different functional gastrointestinal disorders (FGID) remains unclear.

Aim To investigate the prevalence of fructose and lactose intolerance (symptom induction) and malabsorption and their association with clinical gastrointestinal (GI) as well as non-GI symptoms in FGID and the outcome of dietary intervention.

Methods Fructose and lactose intolerance (defined by positive symptom index) and malabsorption (defined by increased hydrogen/methane) were determined in 1372 FGID patients in a single centre using breath testing. Results were correlated with clinical symptoms in different FGID Rome III subgroups. The effectiveness of a targeted saccharide-reduced diet was assessed after 6–8 weeks.

Results Intolerance prevalence across all FGIDs was 60% to fructose, 51% to lactose and 33% to both. Malabsorption occurred in 45%, 32% and 16% respectively. There were no differences in intolerance or malabsorption prevalence between FGID subgroups. FGID symptoms correlated with symptoms evoked during testing (r = 0.35–0.61. P < 0.0001), but not with malabsorption. Non-GI symptoms occurred more commonly in patients with intolerances. Methane breath levels were not associated with constipation using several cut-off thresholds. Adequate symptom relief was achieved in >80% of intolerant patients, irrespective of malabsorption.

Conclusions Fructose and lactose intolerances are common in FGID and associated with increased non-GI symptoms, but not with specific FGID subtypes. Symptoms experienced during breath testing, but not malabsorption, correlate with FGID symptoms. Effective symptom relief with dietary adaptation is not associated with malabsorption. Mechanisms relating to the generation of GI and non-GI symptoms due to lactose and fructose in FGID need to be explored further.


Adverse reactions to food are common in the population and are claimed by up to 67% of individuals with Functional Gastrointestinal Disorders (FGID).[1] They form part of the Rome III definition of Functional Dyspepsia (FD), and are frequent in Irritable Bowel Syndrome (IBS).[2] Food hypersensitivity is often difficult to confirm, but avoidance of specific foods often diminishes symptoms. Possible underlying mechanisms include nutrient maldigestion or malabsorption, chemical or mechanical hypersensitivity, changes in gastrointestinal motility, the enteric microbiome, and immune and psychological responses. Reliable tests are lacking for several of these mechanisms and results may be ambiguous, for example, for tests of malabsorption and allergy. However, there has been recent progress, both in more refined test methodology and in interventional studies.[3,4] Although carbohydrate intolerances, defined as symptoms associated with their ingestion, are probably not the cause of most FGID, the reduced consumption of fermentable saccharides in patients with malabsorption results in symptom relief superior to most pharmaceutical treatments.[5,6] However, the significance of carbohydrate-related symptoms and of malabsorption in FGID remains unclear, as do the optimal diagnostic techniques.[7] Furthermore, the common association of GI intolerances with non-GI reactions in FGID remains unexplained.

In this study, the following issues were examined in a large single-centre cohort of successive FGID patients: (i) How common are lactose and fructose intolerance and malabsorption during breath testing in FGID and its subgroups? (ii) What is the relationship between clinical symptoms and breath test results? (iii) Are non-GI symptoms associated with intolerances? and (iv) What is the symptomatic outcome of a standardised dietary intervention and is this related to malabsorption? Our hypotheses were that fructose and lactose intolerance would be equally common across all FGID, that symptoms generated during breath testing would correlate with the patients' clinical symptoms and that intolerance would be more relevant than only malabsorption in the diagnosis and dietary treatment outcome of fructose and lactose intolerance. We expected a high incidence of non-GI symptoms in patients with intolerances.