Dietary Analysis in Symptomatic Patients with Coeliac Disease on a Gluten-Free Diet: the Role of Trace Amounts of Gluten and Non-Gluten Food Intolerances

Background: Whereas many people with coeliac disease (CD) are asymptomatic when consuming a gluten-free diet (GFD), a proportion continues to experience symptoms. The reasons for this are unclear. Methods: Thirty-nine adult members of The Coeliac Society of New South Wales, all of whom had persistent gastrointestinal symptoms despite adhering to a GFD, were evaluated. Dietary analysis indicated that 22 (56%) were consuming a GFD as defined by the WHO/FAO Codex Alimentarius (Codex-GFD), in which foods containing up to 0.3% of protein from gluten-containing grains can be labelled as `gluten free'. The remaining 17 were following a no detectable gluten diet (NDG)-GFD, as defined by Food Standards Australia. All subjects were required to follow a NDG-GFD during the study. Those in whom symptoms persisted after changing from a Codex-GFD and those who entered the study already on a NDG-GFD began an elimination diet followed by open and double-blind challenges to identify specific non-gluten food or food chemical intolerances. Results: Of 22 patients who switched to a NDG-GFD symptoms resolved in 5 (23%) and were reduced in 10 others (45%). Thirty-one subjects commenced the elimination diet. Symptomatic improvement was experienced in 24 (77%). Subsequent food or food chemical challenges resulted in a mean of five positive challenges per individual. Diarrhoea was the most commonly provoked symptom, followed by headache, nausea, and flatulence. Symptoms were especially provoked by amine, salicylate and soy. Conclusion: The consumption of trace amounts of gluten, traditionally allowed in a Codex-GFD, may be responsible for the continuing symptoms seen in some patients with CD. Further investigation for non-gluten food intolerances should follow if symptoms persist after adherence to a NDG-GFD.