Gluten-Free Food for Treatment of Celiac Disease. Is It Time to Reconsider the Gluten Threshold? A Scoping Review

Background/Objectives. Rules for gluten-free (GF) food varies throughout the world. A maximum gluten level of 20 parts per million (ppm) in GF items is allowed in countries adopting the Codex Alimentarius recommendation, e.g. USA, Canada, UK, and the EU. More stringent criteria (no detectable gluten) are requested in other countries, e.g. Australia. However, only few data are available on the toxicity/safety of gluten traces in the diet of patients with celiac disease (CeD). The aim of this review was to review the scientific background of the gluten threshold in GF food. Methods. Studies on the dose-effect relationship between the amount of low gluten and detectable damage in CeD patients were examined and critically reviewed within the context of the current Codex Alimentarius rules. Results. A gluten dose higher than 10 mg per day, corresponding to 500 g of daily GF products at 20 ppm, may be harmful for most CeD patients. There is wide inter-patient variability in the response to a gluten intake of 10 mg. The potential toxicity of gluten traces < 10 mg/day of gluten remains unclear. Conclusions. The 20 ppm gluten threshold is safe for most patients, however further randomized controlled trials are required to evaluate the effects of 0-10 mg/day of gluten intake and, consequently, the safety of the current threshold at 20 ppm for “hypersensitive” CeD patients. New techniques, e.g. IL-2 measurement after a single-dose gluten challenge, may facilitate the investigation of the gluten dose-response curve, particularly in the low range of gluten intake.