Exposure Sources, Amounts and Time Course of Gluten Ingestion and Excretion in Patients With Coeliac Disease on a Gluten-free Diet

Jocelyn A. Silvester; Isabel Comino; Lisa N. Rigaux; Veronica Segura; Kathy H. Green; Angel Cebolla; Dayna Weiten; Remedios Dominguez; Daniel A. Leffler; Francisco Leon; Charles N. Bernstein; Lesley A. Graff; Ciaran P. Kelly; Carolina Sousa; Donald R. Duerksen


Aliment Pharmacol Ther. 2020;52(9):1469-1479. 

In This Article

Abstract and Introduction


Background: A major deficit in understanding and improving treatment in coeliac disease (CD) is the lack of empiric data on real world gluten exposure.

Aims: To estimate gluten exposure on a gluten-free diet (GFD) using immunoassays for gluten immunogenic peptides (GIP) and to examine relationships among GIP detection, symptoms and suspected gluten exposures

Methods: Adults with biopsy-confirmed CD on a GFD for 24 months were recruited from a population-based inception cohort. Participants kept a diary and collected urine samples for 10 days and stools on days 4–10. 'Doggie bags' containing ¼ portions of foods consumed were saved during the first 7 days. Gluten in food, stool and urine was quantified using A1/G12 ELISA.

Results: Eighteen participants with CD (12 female; age 21–70 years) and three participants on a gluten-containing diet enrolled and completed the study. Twelve out of 18 CD participants had a median 2.1 mg gluten per exposure (range 0.2 to >80 mg). Most exposures were asymptomatic and unsuspected. There was high intra-individual variability in the interval between gluten ingestion and excretion. Participants were generally unable to identify the food.

Conclusions: Gluten exposure on a GFD is common, intermittent, and usually silent. Excretion kinetics are highly variable among individuals. The amount of gluten varied widely, but was typically in the milligram range, which was 10–100 times less than consumed by those on an unrestricted diet. These findings suggest that a strict GFD is difficult to attain, and specific exposures are difficult to detect due to variable time course of excretion.


Coeliac disease is a chronic gluten-responsive immune mediated enteropathy[1] that is treated with a gluten-free diet (GFD).[2] Patients with coeliac disease report high rates of adherence to a strict GFD;[3] however, unintentional gluten exposures may be more common than realised and are distinct from lapses in an otherwise intentionally strict GFD.[4,5] Compared to other chronic health conditions, the treatment burden of coeliac disease is high.[6] The limitations and socio-emotional toll of a GFD are increasingly recognised,[7] which along with high rates of ongoing symptoms and enteropathy on a GFD are driving efforts to develop adjunctive or alternative therapies to a GFD. These include immunomodulatory therapies as well as gluten-digesting enzymes that hydrolyse prolyl-peptide bonds that are resistant to human gastrointestinal luminal proteases.[8]

Recently, tests for gluten in food,[9–11] and gluten immunogenic peptides (GIP) in stool[12,13] and urine[14] have been developed. These immunoassays rely upon the G12 and/or A1 antibodies, which bind GIP—gluten peptides resistant to intraluminal and serum proteases that are recognised by T cells of patients with coeliac disease.[9–12,15] Using these methods, GIP were detected in faeces from 1 in 4 Spanish patients with coeliac disease who reported strict adherence to a GFD and had no sources of gluten ingestion identified on a detailed 3-day dietary questionnaire.[12] These assays quantify gluten excretion, not ingestion. Syage et al have estimated that adults with coeliac disease on a GFD consume a median 141 mg gluten per day through extrapolation from stool GIP concentrations;[16] however, many factors affecting kinetics of GIP excretion (eg food matrices, individual variations, water ingestion) were not accounted for.

Previously, in a sample of community-dwelling adults with biopsy-confirmed coeliac disease who were aiming to adhere to a strictly gluten-free diet, we demonstrated that low concentrations of gluten can be found in the food, urine and stool.[17] In this study we quantified the amount and frequency of gluten exposures; characterised the timing of gluten absorption and excretion; and examined the relationship of gluten exposure to acute symptoms and suspected gluten exposures.