Carlo Catassi; Alessio Fasano

Disclosures

Curr Opin Gastroenterol. 2008;24(6):687-691. 

In This Article

The Treatment: Gluten-free Diet

The cornerstone of treatment of celiac disease is a lifelong adherence to a strict GFD devoid of proteins from wheat, rye, barley, and related cereals. Gluten is, however, a common (and in many countries unlabeled) ingredient in the human diet, presenting a big challenge for celiac disease patients. Gluten-free products are not widely available and are more expensive than their gluten-containing counterparts. Dietary compliance is therefore suboptimal in a large proportion of patients. Furthermore, even when compliance is not an issue, a high percentage of celiac disease individuals on a GFD that are symptom-free and test negative to celiac disease serology show persistence of severe intestinal damage.[15,16] This persistence damage may be in part due to gluten cross-contaminations and lack of information on safe gluten thresholds.

How Much of Gluten is Too Much?

It is almost impossible to maintain a diet with zero gluten content because gluten contamination is very common in food. 'Hidden' gluten (used as a protein filler) may be found in commercially available products, such as sausages, soups, soy sauces, and ice cream. Even products specifically targeted to dietary treatment of celiac disease may contain trace amounts of gluten proteins, either because of the cross-contamination of originally gluten-free cereals during their milling, storage, and manipulation or because of the presence of wheat starch as a major ingredient. Until recently, the potential toxicity of trace amounts of gluten was not clear. This is a hot topic that has not only clinical but also trading and regulatory implications. In northern European countries, up to 100 ppm of gluten is permitted in special food for celiac disease patients as an ingredient. Conversely, a more prudent threshold of 20 ppm has been adopted in North American and southern European countries.

New data are now available on the issue of the gluten threshold. By using a prospective, double-blind and placebo-controlled study design and the quantitative morphometry on small intestinal biopsies as the biomarker of gluten-induced damage, Catassi et al.[15] showed that 50 mg of daily gluten, if introduced for 3 months, was sufficient to cause a significant decrease in the villus height/crypt depth ratio in the small bowel mucosa of treated celiac disease patients. Neither the clinical nor the serological (IgA antitTG and AGA) findings showed a correlation with the minimal mucosal changes induced by these gluten traces. Because of the limited number of patients studied, no firm conclusions could be reached about the potential toxicity of 10 mg gluten/day, which remained a 'grey' area. A recent systematic review of the literature suggested that a daily gluten intake of less than 10 mg is unlikely to cause significant histological abnormalities.[17] These results should be interpreted in light of recent data regarding the consumption of wheat substitutes by celiac disease patients. In a large sample of European celiac disease patients, the median intake of wheat substitutes was 173-268 g/day, whereas 10% of patients consumed 400-531 g/day of these products.[18]

It can be concluded that the previously used 200 ppm value is not a safe threshold because the harmful gluten intake of 50 mg/day could be ingested even by patients consuming a moderate amount (250 g/day) of nominally gluten-free products. Even a 100-ppm threshold is not suitable for generalized use, especially when consumption of wheat substitutes is occasionally as high as 500 g/day. The threshold of 20 ppm keeps the intake of gluten from 'special celiac food' well below the amount of 50 mg/day, which allows a safety margin for the variable gluten sensitivity and dietary habits of patients.

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