Safety of gluten in gluten-free foods

Ciacci and colleagues have misinterpreted published data on the safety of trace amounts of gluten in foods labelled ‘gluten free’. ¹ A referenced double-blind placebo-controlled study did not conclude that 10 mg gluten per day is safe in the diet of a coeliac disease (CD) patient; this study concluded the diet should contain less than 50 mg gluten per day. ² Safety of a therapy implies lack of toxicity for a majority of patients studied, which was seen in this referenced study only for patients who received no additional gluten in their diet. A recent United States Food and Drug Administration safety analysis concluded that <1 ppm gluten was required to protect the greatest number of patients with CD. ³

It is important for clinicians to understand these data, as 10 mg gluten per day represents the amount of gluten ingested in a diet of 500 g food/day, containing 20 ppm gluten, the European and North American gluten-free standard. Ciacci correctly states there is wide variation in sensitivity to gluten among patients, and conveys the widely agreed recommendation that a gluten-free diet should be as strict as possible. Unfortunately, villous atrophy on follow-up biopsy, as the best surrogate marker for disease control, remains present in about one-third of patients. ⁴

Inadvertent gluten ingestion occurs by accidental contamination in kitchens or restaurants, from foods inherently gluten free yet contaminated at source, or from foods labelled ‘gluten free’. Each mechanism of inadvertent gluten ingestion adds to the daily gluten burden for the CD patient. To minimise this burden, the very least that patients should expect is for foods labelled ‘gluten free’ to contain as little gluten as possible. From a practical perspective, what is achievable? Australia and New Zealand have the tightest gluten-free standards internationally; as a result, about 95% of local foods labelled ‘gluten free’ contain <3 ppm gluten. ⁵ Until new therapies are developed for patients with CD, it would be prudent to optimise the only treatment that currently exists, the gluten-free diet.