Study: Even strict gluten-free diets may not completely prevent gluten exposure

an illustration of a "gluten free" label for people with celiac disease
(Image: AdobeStock/Illustration: Fawn Gracey, Boston Children's)

Even a strict gluten-free (GF) diet may not help people with celiac disease completely avoid gluten. That’s the finding of a recent study by Jocelyn Silvester, MD, PhD, and her colleagues at the University of Manitoba, Beth Israel Deaconess Medical Center, and the University of Seville. They sought to determine whether GF diets still contain traces of gluten, a protein in rye, barley, and wheat that can damage the small intestine in people with celiac disease.

“We believe that this is the first time that the gluten content of food as consumed (as opposed to ingredients or packaged foods labeled GF) has been quantified in addition to gluten excreted in stool and urine,” says Silvester, a gastroenterologist in the Celiac Disease Program at Boston Children’s Hospital.

A closer look at GF diets

Celiac disease is a lifelong intolerance to gluten that can prevent proper absorption of nutrients contained in foods and drinks. Although strict adherence to a GF diet is currently the only treatment for celiac disease, its full effectiveness had not been measured until recently. Now, the development of new immunoassay tests to detect harmful gluten peptides makes it possible to quantify how much gluten people with celiac disease actually consume when eating GF foods.

To learn more, Silvester and her colleagues used these immunoassays to test samples of food, urine, and stool from 21 adults. Eighteen of the participants had confirmed celiac disease and had followed a GF diet for the previous 24 months. Another three volunteers without celiac disease ate a diet containing gluten and served as controls.

Researchers call for more feasible celiac treatments

The team found measurable amounts of gluten in close to 10 percent of all of the samples. What’s more, 66 percent of the participants had gluten detectable in at least one sample over a 10-day period. The amount of gluten varied widely, but was typically in the range of milligrams. This was between 10 and 100 times less than what was consumed by people on an unrestricted, non-GF diet.

While troubling, the findings were not unexpected, says Silvester. Indeed, they reveal the challenges that exist in avoiding gluten — even among people who are diligent with their efforts. The results also help explain why some people who follow strict GF diets still experience symptoms of celiac disease.

“Frequent detection of gluten in a ‘gluten-free’ diet suggests that gluten exposure is pervasive,” says Silvester. “This calls attention to the need to find more feasible treatments for people with celiac disease that will be easier to manage and will also be more effective.”

Learn about the Celiac Disease Program.

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