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Systematic review on tolerable levels of gluten for people, medically diagnosed with coeliac disease.

Project Code: T07048;
Publication:

Akobeng, A. K. and Thomas, A. G. (2008). Systematic review: tolerable amount of gluten for people with coeliac disease. Alimentary Pharmacology and Therapeutics. 27: 1044-1052.

31/08/2006

Manachester Children's University Hospitals NHS Trust
Akobeng, A ; Thomas, A

Although avoidance of gluten is necessary for people with coeliac disease (CD), the exact relationship between the quantity of gluten ingested and the development of symptoms and/or mucosal abnormalities is not clearly defined. The aim of this study was to evaluate articles that had investigated threshold amounts of gluten in the diet which people with CD can tolerate, or threshold concentrations of gluten in food products that can safely be consumed by people with CD. We performed a systematic review of studies published between 1966 and March 2006 that had examined the relationship between the amount of gluten ingested or the concentrations of gluten in food products, and the development of symptoms or mucosal abnormalities. Our data sources included Medline, Embase, Cochrane Central Register of Controlled Trials, Cinahl, and reference lists of retrieved articles.

Twelve studies met the review criteria. A daily consumption of 200 mg or more of gluten clearly induced mucosal abnormalities. In two studies, the ingestion of an average of 34 - 36 mg of gluten daily did not cause histological changes or clinical symptoms. However, in one study, a much smaller dose of gluten (1.5 mg daily) triggered symptoms but it was not clear whether the symptoms were associated with mucosal abnormalities. The effect of the consumption of ‘gluten-free’ products with different degrees of gluten contamination was also inconsistent between studies. Whilst some people tolerated current Codex standard ‘gluten-free’ products (less than 200 ppm gluten), others developed histological abnormalities whilst consuming the same products. It is likely that it is the total amount of gluten ingested over time rather than the concentration of gluten in the food products that is important.

The current Codex standard of 200 ppm is not sufficiently protective for all people with CD and so there may be a case for lowering the current concentration of gluten permitted in ‘gluten-free’ food products. We, however, found insufficient evidence to allow us to propose a definitive clinical threshold dose of gluten or a threshold concentration of gluten in food products that would be tolerated by all people with CD. It appears that the amount of tolerable gluten varies among people with CD but the reason for this is unclear.

Future studies should be randomised controlled trials and should address the following points:

1. the exact amount of gluten that can be tolerated by people with CD and over what period of time.

2. the exact concentration of gluten in wheat-starch ‘gluten-free’ products and all other foods that can be tolerated by people with CD.

3. the potential reasons (e.g. genetic variability) that may explain the variable response to gluten.

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