Safety of Gluten-Free Restaurant Food and Personal Testing Devices

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Published October 7, 2020

A study on this topic got a lot of attention when it was presented at a gastroenterology conference this fall. Researchers claimed their study showed that a third of “gluten-free” restaurant food was not actually gluten-free. But before you panic and decide never to eat out again, here are some facts about the study and additional information to keep in mind:

The study

Data was gathered over an 18-month period by 804 people, who performed a total of 5,624 tests using the Nima sensor testing device. The primary conclusion of the study was that one-third of restaurant foods labeled gluten-free contained at least 20 ppm of gluten. (While there is no regulated threshold for gluten-free claims in the food service industry, it is reasonable to expect that foods with a gluten-free claim would meet the 20 ppm threshold that the FDA has established for packaged foods). This study claimed that a positive result with the Nima sensor indicated the presence of gluten at 20 ppm or greater.

Additional considerations

The Nima sensor provides only 2 possible results: “no gluten” or “gluten at 20 ppm or more” (in other words, not gluten-free). However, independent work by the Food Allergy Research and Resource Program (FARRP), published in the Journal of Food Protection, indicated that the Nima sensor detected gluten at 5 ppm approximately 30% of the time, and at 10 ppm over 50% of the time, across a number of different types of food. This means that even though the amount of gluten in these foods was below the 20 ppm cutoff mark, according to the Nima sensor it was categorized as containing gluten and not gluten-free. In some specific food types (corn puffs and oatmeal), the Nima sensor produced false positive results 33% of the time – meaning a positive result for gluten was obtained when no gluten was present in one-third of these samples.

The performance characteristics of the Nima sensor make it impossible to determine what fraction of the restaurant samples tested in this study actually contained 20 ppm of gluten. Also keep in mind that when a sample of a restaurant meal is tested using the Nima sensor, the test results reflect just that: the one sample tested, not the entire serving of the food item, or the entire meal.

GIG recommends caution in the interpretation of this data, and that future studies of this type use appropriately validated testing methods.

To maximize your confidence in gluten-free restaurant dining:

Choose restaurants that have been certified by GIG’s Gluten-Free Food Service (GFFS) program:

Ask questions and follow these tips:

Original study:

FARRP study:








This was Hot Topic Safety of Gluten-Free Restaurant Food and Personal Testing Devices, a brief review of the Nima sensor testing device. For more information about living gluten-free, check out our website!