Royal Prince Alfred Hospital Royal Prince Alfred Hospital
Allergy Unit

Student research


Assessment of gluten-free diets in an Australian population with coeliac disease and their impact on symptoms, mucosal, nutritional and metabolic parameters.

by
Kim Faulkner-Hogg
Doctor of Philosophy (PhD), The University of Sydney
Supervisors: Robert Loblay, Warwick Selby
January 2004

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Abstract from PhD thesis

Coeliac disease (CD) is a gastrointestinal disease caused by a hypersensitivity to gluten in genetically predisposed individuals. A gluten-free diet (GFD) is expected to relieve symptoms and reverse the characteristic villous atrophy. Persistent symptoms and ongoing mucosal pathology, observed in a subset of people with CD, are usually attributed to non-compliance with the GFD.

Patients adhering to a GFD rarely eat no gluten at all. According to the international Codex Alimentarius standards, a food labelled 'gluten free' can contain up to 0.3g/100g of protein from a gluten containing grain. On a GFD based on these standards, patients have been found to ingest 5-100mg (average 34mg) per day of gluten. In addition to these small amounts, many patients also have occasional inadvertent exposure to foods containing larger amounts of gluten. Australia followed the Codex labelling standards until 1995; since then, foods can only be labelled 'gluten-free' if they contain no detectable (<0.003%) gluten (NDG).

To determine whether persistent symptoms in some coeliac patients on a GFD were due to ingestion of small amounts of gluten allowed in foods labelled 'gluten-free', or to other non-gluten food intolerances, 39 symptomatic subjects were recruited. Of 22 adhering to a Codex-GFD at the outset, symptoms resolved completely in 5 and improved significantly in 10 after changing to a NDG-GFD for > 3 months. Of 26 patients who undertook a diagnostic elimin-ation diet to investigate possible non-gluten food intolerances, 24 improved significantly and 19 completed a challenge protocol to identify the food substances responsible for symptoms.

To investigate the effects of ingestion of small amounts of gluten on the small bowel mucosa, nutritional status and bone mineral density (BMD), 48 coeliac patients were recruited and asked to follow a NDG-GFD for a 2-year period. Their small bowel biopsies, BMD, nutritional parameters and dietary intake were examined at entry, 12 months and 2 years. The NDG-GFD was found to be nutritionally adequate and no subject was malnourished. Twenty-two patients had an abnormal small bowel biopsy at some point in the study period, 5 of which were abnormal throughout. This was unrelated to gluten intake, and had no detrimental effect on symptoms, nutritional status or BMD. Long-term avoidance of the small amounts of gluten permitted on a Codex-GFD did not result in improvement in the small bowel pathology in those with an abnormal biopsy at the outset.

Conclusions

(1) Persistent symptoms experienced by some patients with CD may be due to the consumption of small amounts of gluten that are permitted on a Codex-GFD. Such individuals may be regarded as belonging to a 'more sensitive' subgoup.

(2) Non-gluten food intolerances can cause symptoms in patients who remain symptomatic despite careful adherence to a NDG-GFD.

(3) The NDG-GFD is nutritionally adequate.

(4) Small bowel mucosal abnormalities can persist in some patients independent of symptoms and regardless of adherence to a NDG-GFD.

(5) Nutritional status and BMD are not adversely affected in the longer term (2 years) by the persistence of villous atrophy in coeliac patients adhering to a NDG-GFD.