Research Study on the Establishment of a Safe Gluten Threshold for Celiac Disease Patients

Celiac.com 01/10/2007 – Celiac disease researchers in Italy and at the Center For Celiac Research in Baltimore, Maryland have conducted a multi center, double-blind, placebo-controlled, randomized trial involving 49 adult individuals who have biopsy-proven celiac disease, and who have been on a gluten-free diet that contains less than 5mg of gluten per day for a minimum of two years. The aim of this study was to determine whether there is a safe threshold for prolonged, daily exposure to minute amounts of gluten. Subjects in the study were divided into 3 groups which were given daily capsules that contained 0mg, 5mg or 50mg of gluten. They were given biopsies and serological screening before and after a gluten challenge. One patient who was given 10mg of gluten daily did experience a clinical relapse, but at the end of the study no significant differences in the IEL count were found between the 3 groups, which lead the researchers to conclude that "(t)he ingestion of contaminating gluten should be kept lower than 50 mg/d in the treatment of celiac disease."

This study is in line with past gluten threshold studies, and to help you put the amounts of gluten used in the study into perspective, and to demonstrate why the 20 ppm for naturally gluten-free products used in the Codex Alimentarius gluten-free standards is considered to be a safe threshold for those with celiac disease, the following discussion will attempt to quantify just how much gluten it takes to make 50mg.

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The amount of gluten contained in your average 30g slice of wheat bread is around 4.8 grams, or 4,800 milligrams (amount of gluten in wheat bread is normally 10% by weight). If you divide 4,800 by 50 it equals 96, so if divide an ordinary slice of bread into 96 pieces, that is roughly how much daily gluten, according to this study, appears to be safe for those with celiac disease.

Here is a formula that can be used to determine the number of milligrams of gluten in foods based on the parts per million (ppm) of gluten in the product. The formula is: Products ppm times the number of grams of food divided by 1,000 which equals the number of milligrams. The Codex Alimentarius specifies that naturally gluten-free products contain less than 20ppm, and products that are rendered gluten-free such as Codex quality wheat starch contain less than 200ppm. Using this formula we can determine how many slices of 20ppm and 200ppm gluten-free bread a person with celiac disease would have to eat to consume 50mg of gluten. Here is the math:

The goal of this study (and this article) is not to encourage people with celiac disease to eat gluten. The reality is that cross-contamination of supposedly gluten-free products is very common, and many of us who are on gluten-free diets still unknowingly ingest tiny amounts of gluten on a daily basis. Studies like this can help provide some sense of perspective with regard to how concerned one should be about minute gluten ingestion, and hopefully this article will help you to understand exactly what the 50mg threshold found in the study means. An article called Gluten-phobia in the Winter 2007 issue of Journal of Gluten Sensitivity further addresses what can happen when someone takes their fear of gluten too far and lets it disrupt their life in ways that are so psychologically unhealthy that the negative effects to the author and those around her may actually rival those of the disease itself.

Comments by Susan Phillips Clavarino:

I read with interest your remarks about the Catassi/Fasano study. As an active member of the AIC (Association of Italian Celiacs), sponsors of the study, and as the person responsible for revising the language of the text for publication…the study does raise some serious queries about background gluten contamination and its impact on the celiac intestine. When the authors remark that the IELs do not show a difference among the three groups of celiacs on long term gluten free diet (though not compared to the non celiac disease controls), they point out that the villous height/crypt depth ratio is a more valid and more sensitive marker of gluten trace contamination in celiacs on long-term dietary treatment. They also remark that "Despite the restricted criteria adopted in this study, the baseline duodenal biopsy results showed evidence of histologic damage (decreased median Vh/celiac disease count and increased median IEL count in adult celiac disease patients receiving long-term dietary treatment. Furthermore, 4 of 49 subjects had to be excluded from the protocol because severe enteropathy (obscuring the possible effects of the micro challenge) was detected at the baseline evaluation. These results confirm that an abnormal small bowel morphology persists in a significant proportion of celiac disease patients treated with a gluten-free diet, despite full resolution of their symptoms..."(due to)"... the ongoing ingestion of gluten, either deliberate or inadvertent, causing persistent inflammation in the small-intestinal mucosa..." etc.

As all medically diagnosed Italian celiacs receive a free monthly allowance of naturally (i.e. no wheat starch) gluten free products containing less than 20 ppm from the Italian government health service, and as all the volunteers for the study considered themselves to be healthy (otherwise they would certainly not have volunteered), the finding that 4 out of 49 had to be excluded for severe enteropathy and that histologic damage persists in a significant proportion of adult celiac disease patients on long-term gluten-free diet, besides the other findings of the study (i.e. that 50 mg of gluten per day for only 3 months of trial results in measurable intestinal damage, while there was significant improvement in the placebo group during the strictly monitored trial) is not reassuring. In the light of the Catalan study on the amount of gluten-free dietary foods actually consumed by celiacs in Europe - together with the constant risk of involuntary background contamination and the varying degrees of individual sensitivity - the absolute maximum threshold of ppm in gluten-free products must be kept below 20 ppm. This is a very far cry from the current wording of the Codex Alimentarius which is based on the old standard of the nitrogen content in food.

I hope that these words may help to clarify the importance of the work done by Profs. Catassi and Fasano, the Association of Italian Celiacs, the study by the Catalan research group (previously cited on your website), and the need for further research and information as to the impact of micro-traces of gluten on celiac disease and its complications so as to ensure that celiacs may make fully informed decisions about their dietary choices.