One-third of restaurant food labeled gluten-free contains detectable gluten, according to crowdsourced data1 in the United States. Contamination was even higher in pizza and pasta, occurring in half of all samples. Gluten was detected more often at dinner time (34 percent) than breakfast (27 percent).
The study from Columbia University, New York, included 5,624 tests by 804 people using Nima portable gluten detectors. The samples occurred across the country between August 2016 and January 2018.
High rates of contamination appeared across all restaurant types and regions. However, higher rates appeared in the Northeast than the West. Rates were lower at casual and fast casual restaurants than at quick service.
Nima devices are highly sensitive, detecting gluten accurately down to 20 parts per million (ppm), the level considered safe for people with celiac. They frequently detect gluten below 20 ppm, so many of the items testing positive in this study may have been safe to eat. It is unclear whether contamination levels detected in this study would be sufficient to cause intestinal damage or symptoms in people sensitive to gluten.
This crowdsourced data provided the largest study of gluten contamination in restaurant food to date. The risk of getting glutened while dining out reduces quality of life and causes anxiety for people with celiac. These findings raise concern, but more research is needed to understand how dangerous the levels of contamination are.
Van Waffle is a freelance journalist based in Waterloo, Canada, and research editor for Gluten-Free Living. He blogs at vanwaffle.com.
- Lerner BA, Phan Vo LT, Yates S, Rundle AG, Green PHR, Lebwohl B. Detection of gluten in gluten-free labeled restaurant food: analysis of crowd-sourced data. American Journal of Gastroenterology. 2019;114:792-797. doi:10.14309/ajg.0000000000000202.