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Celiac Disease and the Gluten-Free Diet: How Much is Too Much of a Gluten Thing?

1 August 2008


Celiac disease is being recognized and diagnosed more frequently with the help of improved serologic indicators and biopsy techniques. With dietary intervention being the only definitive treatment, more research is needed to define the potentially toxic threshold of gluten marking the amount that prevents intestinal histological recovery. In addition, with a dietary noncompliance rate estimated at greater than 50%, more research needs to be done on influencing factors and issues surrounding the difficulties of dietary compliance.

Background: Celiac disease (CD) has an intensely complex pathophysiology that involves both environmental factors and genetic components. It is identified by the inability to ingest gluten without having an immune response in genetically susceptible patients. Research has indicated that genetic susceptibility alone does not result in CD, that there is a certain environmental aspect that must be present as well. With the right genetics and environmental exposure, gluten ingestion will cause intestinal inflammation, villous atrophy, and flattening of the intestinal mucosa.

There are many approaches to diagnosing celiac disease. While small bowel biopsy remains the gold standard for diagnosis, serologic tests are still the initial part of the evaluation. The most sensitive and specific tests currently available are the immunoglobulin A anti tissue transglutaminase (IgA tTG) and IgA endomysial antibody (IgA EMA). In the rare circumstance that a patient is IgA deficient, however, these serologies are unreliable and an IgG based assay must be used.

The only definitive treatment for celiac disease is to remove gluten from the diet. The problem is there is no defined threshold of gluten contamination and the potential toxicity of even trace amounts remains unclear. Patients need to first understand which products contain gluten, maintain strict adherence to the diet, and continue periodic follow up with both a celiac trained registered dietitian and their primary care provider. As more people are being diagnosed with celiac disease, more gluten free products are becoming available. Additionally, more research is being done on the effects of the gluten free diet with regards to its effect on intestinal mucosa as well as its psychosocial effect on the patient.

Codex Alimentarius was established in the 1960’s by the World Health Organization and the Food and Agriculture Organization of the United Nations as a way of formulating and implementing food safety standards worldwide. A Spanish doctor devised and presented to the organization an enzyme-linked immunosorbent assay (ELISA) method of detecting gluten levels as low as 3.2 parts per million (ppm). And while more studies are needed, current research can be used to temporarily deduce a safe daily gluten threshold. Exposure to gluten on a gluten free diet (GFD) is not as easily measured as there is limited data available on the consumption of gluten free products as well as to what degree patients substitute traditional bread, pasta, and other cereal based products for the their gluten free alternatives.

Objective: To establish an upper limit of potentially toxic gluten levels for celiac patients and to uncover the factors that negatively impact gluten free dietary compliance.

Methods: An extensive online search was done using Ovid, PubMed, and UpToDate. Search terms used were Celiac disease, gluten-free diet, gluten threshold, quality of life, dietary compliance. Articles were limited to human subjects and those written in English and published within the last five years.

Results: Studies continue to have varying results but current research suggests that 30-50 mg of ingested gluten per day can be considered safe clinically and histologically for people who suffer with Celiac disease. This is roughly 100-160 parts per million of gluten. Even if celiac patients tried to abide by the most recent findings however, there are no current guidelines in the United States regulating labeling indicating gluten content. The only safe approach is to consume fruits, vegetables, and meat while adding moderate ‘gluten-free’ products as the gluten content is not yet regulated.

Dietary compliance was shown to be difficult for a multitude of reasons. Women tend to adhere to the required diet more often than men, but also have been found to have higher rates of anxiety, depression, and lower self-rated quality of life scores. Cost analysis indicated that gluten-free products cost approximately three times their regular wheat-based counterpart.

Conclusion: Maintaining a gluten-free diet is difficult and can be costly. Maintaining gluten intake between 30-50 mg per day appears to be safe. Insuring gluten intake remains at that level, consumption should be mostly fruits, vegetables, and meat with minimal addition of store bought gluten-free products. No study has been done evaluating the effect of gluten-free product cost on dietary compliance but with the results of the cost analysis, it can be implied that this added burden would likely have a negative impact. Increased product availability at more reasonable prices would likely improve adherence. Finally, there is an increased need for improved dietary instruction as well as support for celiac patients in order to help ease or even alleviate anxiety and other issues surrounding dietary compliance.


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