Safe gluten threshold for patients with celiac disease: some patients are more tolerant than others

Departments of Gastroenterology and Alimentary Tract Surgery and Pediatrics
Tampere University Hospital
PO Box 2000
FIN-33521 Tampere
Finland
E-mail: pekka.collin{at}uta.fi

Dear Sir:

The long-expected first randomized controlled study of a microgluten challenge in patients with celiac disease has been published by Catassi et al (1). The authors stated that 50 mg gluten/d is harmful in celiac disease patients, whereas 10 mg/d is not. The results are based on a small but significant change in the small-intestinal mucosal villous height crypt depth ratio, even though the biopsy specimens did not show mucosal cell infiltrativity or accumulation of inflammatory cells—the known first effects of the disease on gluten ingestion. The question of what happens at doses between 10 and 50 mg/d (eg, a dose of 25 mg/d) remains.

A diet entirely free of gluten contamination would of course be ideal, but today it seems to be unrealistic; even naturally gluten-free products may contain significant amounts of gluten (2). Furthermore, too strict limits might lead to the poor availability of gluten-free products, which again would hamper overall dietary compliance. The study by Catassi et al also implies that minor gluten contamination was not harmful to most of the patients.

In Finland, the current Codex standard of 200 ppm (mg/kg) seems to not be too high; at this dose, mucosal recovery is complete and the quality of life of celiac disease patients is not different from that of the general population (3). In fact, the mean ratio of villous height to crypt depth was higher than in the study by Catassi et al, 3.2 and 2.5, respectively (4). Because most of our gluten-free products contained <200 ppm, we concluded that 100 ppm would be a safe limit (2). The daily ingestion of gluten might also then remain well below 50 mg, at least in Finland.

Clearly, more studies are needed to settle on a safe limit of gluten contamination in gluten-free products. In the meantime, what are the clinical implications of the current studies? It appears that even occasional dietary lapses may slow down or prevent mucosal recovery (3, 4). Whether the safe limit of gluten contamination should be 0, 20, 50, or 100 ppm remains to be seen. As the study by Catassi et al (1) showed, celiac disease patients respond individually to small amounts of gluten. The individual variability denotes that the treatment should be individual too. Here, we emphasize the role of a control biopsy sample taken from adult celiac disease patients consuming a gluten-free diet. Although a biopsy is not usually required to establish a diagnosis, it is important to confirm mucosal integrity. A clear improvement in mucosal integrity after 1 y of a diet indicates that the diet is gluten-free enough to render mucosal recovery. In conclusion, the results of this interesting pilot study need confirmation before firm conclusions can be drawn about the safe limit of gluten ingestion.

ACKNOWLEDGMENTS

The authors had no conflicts of interest to declare.

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