Exposure sources, amounts and time course of gluten ingestion and excretion in patients with coeliac disease on a gluten‐free diet

Summary 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.