How Risky Are Shared Fryers? New Study Offers Real-World Data for People with Celiac Disease

LOS ANGELES, Oct. 20, 2026 /PRNewswire/ -- 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.

Overall, 93.9% of samples contained less than 20 parts per million (ppm) of gluten, including all 43 tortilla chip samples. Only 6.1% exceeded 20 ppm, all of which were French fries. None of the samples from establishments reporting daily fryer oil replacement exceeded 20 ppm.

"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
Of the 98 foods tested, 92 samples, or 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, or 6.1%, exceeded 20 ppm, demonstrating that gluten cross-contact can and does occur in shared fryers. Among those six samples, concentrations ranged from 29.6 ppm to greater than 80 ppm.

Results differed by food type. All 43 tortilla chip samples measured below 5 ppm, the laboratory assay's limit of quantification. All six samples exceeding 20 ppm were French fries. Among the 55 French fry samples tested, approximately 11% exceeded 20 ppm.

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.

From "Safe or Unsafe" to Understanding Risk
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."

For that reason, the researchers are not recommending that people with celiac disease begin routinely eating foods prepared in shared fryers. Rather, these findings provide new evidence that patients, families, dietitians, and clinicians can use when discussing risk and making individualized decisions.

What This Means for People with Celiac Disease
"This is about giving people better information, not taking away precautions," Weisbrod said. "Someone may look at these data and decide that avoiding shared fryers remains the right choice for them. Someone else, after talking with their dietitian or physician, may make a different decision in a particular situation. The goal is to give people with celiac disease and their healthcare providers better evidence to inform those decisions."

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.

Media Contact:
Emily Piken
Celiac Disease Foundation
[email protected] 
310.905.3437 x106

SOURCE Celiac Disease Foundation