Public Release: 

Study measures gluten in gluten-free labeled restaurant food

Columbia University's Mailman School of Public Health

April 5, 2019 -- Even tiny amounts of gluten in foods are troublesome for people with celiac disease, and restaurants may be the hardest places to avoid the protein, finds a study by Benjamin Lebwohl, MD, MS, Celiac Disease Center at NY-Presbyterian Hospital and assistant professor of medicine and epidemiology at Columbia Mailman School. More than half of gluten-free pizza and pasta dishes in restaurants tested positive for the presence of gluten; about one-third of supposedly gluten-free foods had detectable gluten. Results are published in the American Journal of Gastroenterology.

"Patients have long suspected that gluten contamination in restaurant foods is a frequent occurrence, and these results support that," said Lebwohl. "Our findings suggest that pizza, pasta and foods served at dinner were more likely to have a problem."

Lebwohl used data uploaded by users of the portable device Nima Gluten Sensor which restaurant patrons use to test foods. The manufacturer supplied 5,624 food tests by 804 users over 18 months. The research showed 32 percent of tests revealed detectable gluten in dishes that were supposed to be gluten-free.

Gluten-free pasta samples were positive in 51 percent of tests; gluten-free pizza contained gluten for 53 percent. Gluten was detected in 27 percent of breakfasts, 29 percent of lunches and 34 percent of dinners.

There are limitations to the data, notes Lebwohl. "Users may have uploaded results that surprised them the most." Also, the device is very sensitive. To be labeled gluten-free in the U.S., a product must contain less than 20 parts per million. "The device can detect levels as low as 5 to 10 ppm, which most do not consider clinically significant, so a 'gluten found' result does not necessarily mean 'unsafe for celiac disease.' The device also does not detect certain forms of gluten, such as fermented gluten. So both false positives and false negatives will affect this estimate."

Lebwohl suspects that gluten-free foods are inadvertently contaminated, and "the solution may be better education for food preparers."

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The study was supported by the National Institutes of Health (Small Business Innovation, DK105770) and National Institute on Aging (1R01AG049970-01A1).

Columbia University Mailman School of Public Health

Founded in 1922, the Columbia University Mailman School of Public Health pursues an agenda of research, education, and service to address the critical and complex public health issues affecting New Yorkers, the nation and the world. The Columbia Mailman School is the third largest recipient of NIH grants among schools of public health. Its over 450 multi-disciplinary faculty members work in more than 100 countries around the world, addressing such issues as preventing infectious and chronic diseases, environmental health, maternal and child health, health policy, climate change & health, and public health preparedness. It is a leader in public health education with over 1,300 graduate students from more than 40 nations pursuing a variety of master's and doctoral degree programs. The Columbia Mailman School is also home to numerous world-renowned research centers, including ICAP and the Center for Infection and Immunity. For more information, please visit http://www.mailman.columbia.edu.

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