Approximately 1 in 9 French fry orders exceeded the FDA’s 20 ppm gluten-free threshold, while all 43 tortilla chip samples tested below 5 ppm.
LOS ANGELES, Calif., Tuesday October 20, 2026 —
A new multi-center study led by the Celiac Disease Foundation, in collaboration with researchers and clinicians from Children’s Hospital Colorado, Columbia University Medical Center, Mass General Brigham for Children, the University of Chicago Celiac Disease Center, Vanderbilt Health, and Bia Diagnostics, provides some of the most comprehensive real-world data to date on gluten cross-contact in foods prepared in shared fryers.
The study, “Shared Fryers May Not Always Be as Risky for Gluten Cross-Contact in Celiac Disease as Dietary Guidance Suggests,” was published today in Nutrients.
Researchers tested 98 samples of naturally gluten-free foods, including 55 orders of French fries and 43 orders of tortilla chips, prepared in fryers that were also used for gluten-containing foods. Samples were collected from food service establishments across 14 U.S. states under routine, real-world operating conditions.
Among the 55 French fry orders tested, approximately 11% exceeded 20 parts per million (ppm) of gluten, the threshold established by the U.S. Food and Drug Administration for foods labeled gluten-free. All 43 tortilla chip samples tested below 5 ppm, the laboratory’s limit of quantification. Overall, 92 of the 98 samples (93.9%) contained less than 20 ppm, demonstrating that gluten cross-contact risk varies across foods prepared in shared fryers.
“This study is not a green light to eat from any shared fryer,” said Vanessa Weisbrod, Chief Programs Officer at the Celiac Disease Foundation and lead author of the study. “What it gives our community is something we have been missing: real-world data. People with celiac disease make decisions about cross-contact every time they eat outside their homes, often without evidence to help them understand the magnitude of that risk. These findings can help move us from blanket assumptions toward informed conversations with healthcare providers about risk, frequency of exposure, and individual circumstances.”
What the Researchers Found
Results differed by food type. Among the 55 French fry samples tested, six (approximately 11%) exceeded 20 ppm of gluten, with concentrations ranging from 29.6 ppm to greater than 80 ppm. All 43 tortilla chip samples measured below 5 ppm, the laboratory assay’s limit of quantification.
Across all 98 samples, 92 (93.9%) contained less than 20 ppm of gluten, the threshold used by the U.S. Food and Drug Administration for foods labeled gluten-free. Six samples (6.1%) exceeded that threshold, demonstrating that gluten cross-contact can and does occur in shared fryers.
Fryer management practices also matter. None of the 39 samples collected from establishments reporting daily oil replacement exceeded 20 ppm, compared with four of 35 samples from establishments reporting weekly oil replacement. This difference was statistically significant, although the observational study cannot establish that oil-change frequency itself caused the difference.
All samples were analyzed by Bia Diagnostics, an ISO 17025-accredited laboratory in Vermont, using the R-Biopharm RIDASCREEN® Gliadin R5 sandwich ELISA according to AOAC International Official Method 2012.01. Each food sample was homogenized separately in its entirety before a 1-gram test portion was analyzed. Samples were not pooled or combined.
“For years, patients with celiac disease have been given very categorical guidance about shared fryers, largely because we have had limited real-world data to quantify the exposure,” said Edwin Liu, MD, a study co-author from Children’s Hospital Colorado. “These findings don’t tell us that every shared fryer is safe. They tell us that the risk is not the same in every situation. That distinction is important as we work toward more evidence-based counseling that protects patients while also recognizing the realities of living with celiac disease.”
The study builds on earlier research examining gluten cross-contact in shared fryers, including work led by dietitian Tricia Thompson of Gluten Free Watchdog, which provided some of the first real-world evidence that gluten cross-contact can occur when French fries are prepared in shared fryers. Research by Katharine Parsons and colleagues at Brigham Young University also demonstrated gluten transfer through shared fryer oil. The new, larger study builds on this body of evidence by examining a broader range of real-world restaurant samples and factors that may contribute to differences in gluten exposure.
Understanding Gluten Cross-Contact Risk in Shared Fryers
People with celiac disease are commonly advised to avoid shared fryers because gluten-containing breading or batter may contaminate fryer oil and transfer gluten to otherwise gluten-free foods. However, relatively little real-world evidence has been available to quantify how frequently this occurs or the magnitude of gluten exposure when it does.
“For people with celiac disease, dining decisions are rarely as simple as ‘safe’ or ‘unsafe,’” said Meghan McKeon, MS, RD, CSDH, Senior Director of Education at the Celiac Disease Foundation. “These findings give us better information to help patients understand and weigh risk. A gluten concentration is only one piece of the picture. We also need to consider how much someone eats, how often an exposure occurs, and how it fits into their overall gluten exposure. The goal is to give people the evidence and context they need to make informed decisions with their healthcare team.”
These findings do not establish that foods prepared in shared fryers are safe for people with celiac disease or support a general change in recommendations to avoid shared fryers. Instead, they provide new evidence to help patients, families, dietitians, and clinicians better understand the variability of gluten cross-contact and the need for continued precautions. Additional research is needed before these findings can inform changes to dietary guidance.
What This Means for People with Celiac Disease
“The study demonstrates that gluten cross-contact in shared fryers is not uniform, but it also confirms that French fries prepared in shared fryers can contain gluten above the FDA’s 20 ppm threshold,” Weisbrod said. “People with celiac disease should continue to take precautions when dining out, including asking how foods are prepared and whether dedicated fryers are available. Our goal is to build the evidence needed to help patients and their healthcare providers better understand risk and make informed decisions without compromising food safety.”
Researchers say the findings also underscore the need for additional study. Larger studies that repeatedly sample the same fryers over time and examine additional food-service practices could help further characterize cross-contact risk. Future studies that combine measured gluten exposure with clinical outcomes may also help researchers better understand how different sources of gluten exposure contribute to long-term health.