Achieving a ‘gluten free’ diet is an almost impossible task due to contamination and inadvertent consumption, according to researchers who are calling for the term to be rebranded as a ‘gluten restricted’ diet.
Presented at DDW 2018, new findings from a Canadian study of people with coeliac disease following a gluten free diet show that 66% were unknowingly exposed to gluten over a ten day period.
The ‘DOGGIE BAG’ trial of 18 people who had followed a gluten free diet for two years used industry-standard ELISA tests to measure the presence of gluten immunogenic peptides (GIP) in retained samples of all food consumed by participants over a ten day period. GIP levels were also measured in participants stool and urine.
Despite all participants believing they had strictly followed a gluten free diet, gluten exposure was detected on at least one occasion for 12 of the 18 participants. Overall, 8% of food sample, 11% of stool samples and 6% of urine sample tested positive for GIP.
Study investigator Dr Jocelyn Silvester a Canadian gastroenterologist now working at Celiac Research Program, Harvard Medical School, Boston, said it was notable that tissue transglutaminase (TTG) levels did not correlate with gluten exposure, and 40% of the participants had signs of persistent mucosal damage (Marsh 3a).
“Gluten is out there, it is pervasive and inadvertent moderate gluten exposures are likely to be common,” she said.
“This raises the question of the gluten free diet and whether or not this is an aspirational goal. It’s important to step back a bit and see that the ‘gluten free diet’ as we understand it is not eliminating all gluten.”
“And so perhaps we need a rebranding exercise – to call it a gluten restricted or gluten limited diet might be a better term,” she added.
Speaking at the same session, paediatric gastroenterologist Dr Alfonso Rodriguez-Herrera, of Seville, Spain, said it was not surprising that inadvertent gluten exposure was common among people with celiac disease because gluten was widespread and almost indestructible. Small amounts of gluten were sometimes present even in ‘gluten free’ foods and its immunogenic properties were not easily eliminated by cooking, he said.
Only small amounts – as little as 50mg – of gluten could contribute to inflammation and mucosal damage, and many people were inadvertently exposed to such levels of gluten from things such as lipstick, sauces, postage stamps, sweets, soups and malted beverages, he noted.
Most people with gluten contamination were confident they were ‘gluten free’ and almost 70% did not report any symptoms, he added.
A campaign mounted by coeliac groups in Spain had raised awareness of inadvertent gluten exposure though ‘cross-contamination’ in kitchens and restaurants via items such as toasters, serving spoons and even in cracks in wooden tables.
Dr Herrera said GIP tests now offered reliable checks for gluten exposure via stool and urine, and it was unrealistic to rely on diet questionnaires or serology as guides to gluten exposure. He noted that in one recent study 75% of patients with positive GIP tests had negative TTG serology.
“Objective monitoring of gluten contamination in the diet is now possible. GIP testing will be available in hospitals but also at home and will empower patients and give them more autonomy,” he concluded.