One study found 32% of restaurant foods labeled "gluten-free" still contain it.

By Lauren Wicks and Zee Krstic
Updated: April 23, 2019
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UPDATE: Last year, we covered the news of a study (below) that found people who attempted to remove gluten from their diets still had troubling amounts in their system. But the researchers were not able to determine where, exactly, it was coming from. Now, we may have more clues.

A new study, published in the American Journal of Gastroenterology, found that upwards of 32% of restaurant foods labeled "gluten-free" still contained a certain amount of the cereal proteins. The study used crowd-sourced data from more than 5,500 tests of a portable gluten-detecting device called Nima, and found the worst offenders were pizza and pasta—with more than 50 percent of samples containing at least some gluten.

According to the study, fast-food restaurants were more likely to serve products with undetected gluten than casual or fast-casual dining establishments. And interestingly enough, restaurants in the Northeast were more likely to have gluten-containing menu items labeled "gluten-free" than those on the West Coast. 

"We all want people to be vigilant, but not too worried," lead author Benjamin Lerner, MD, told USA Today. "If you have celiac disease or it's harmful for you to ingest gluten, you should feel comfortable asking the waiter how things are prepared."

The Celiac Disease Foundation, in a statement on the study, said that it offered compelling evidence of the challenges of maintaining a strict, gluten-free diet." They also noted that since this study was crowd-sourced, testers may have chosen items they suspected contained gluten and the results "may not be reflective of all gluten-free restaurant foods." 

Celiac Disease Foundation Medical Advisory Board member Daniel Leffler, MD, said, “This is a very clever study done that unfortunately confirms what we have long suspected, which is that there is no such thing as a gluten-free diet.”

The original article, published April 5. 2018, continues below:

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New research released by the American Journal of Clinical Nutrition reveals that most gluten-free dieters are likely consuming a lot more gluten than they think—even when they try to avoid gluten altogether.

For many, the fact that gluten is still popping up in their carefully cultivated diets is more than irksome—it's downright dangerous. Those with celiac disease could experience life-threatening side effects, including on-the-spot reactions such as nausea, rashes, or cramping, to more serious conditions like bone loss or an increased risk of cancer.

To get a better sense of how much gluten was being consumed, the team of researchers split dieters into two groups—one comprised of people with celiac disease, and another without any dietary restrictions. Both of the groups were put onto a gluten-free diet and were regularly tested for gluten exposure using their stool and urine samples.

RELATED: What Exactly Is Gluten?

Despite being on a stringent gluten-free diet, both of the study's groups ended up consuming between 244 and 363 milligrams of gluten each day. Those who regularly eat gluten often consume upwards of 10,000 milligrams per day, however professionals recommend celiac patients keep consumption to under 10 milligrams to be safe.

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The published report points out that anything more than that amount can lead to chronic intestinal damage.

While it's clear that gluten-free diets might not be as effective as we'd hoped, the new research does not provide a clear answer as to where the gluten is coming from. It could stem from cross-contamination of prepared foods, or foods that are marketed as gluten-free but actually are not.

RELATED: 14 Gluten-Free Recipes That Don't Feel Low Carb

Shoppers often take a "gluten-free" promise at face-value—but brands have been known to mislead consumers. General Mills faced major backlash in 2015 when they recalled nearly two million boxes of "gluten-free" Cheerios after it turned out the product was made with wheat flour, causing some shoppers to experience serious reactions.

For now, gluten-free dieters are going to continue the hard fight of avoiding the nearly ubiquitous protein. And this new research proves that the best method of avoiding gluten might be to make dishes from scratch. Cooking Light has published an entire how-to cookbook which can help you lead a healthy gluten-free lifestyle, available here.

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