Poor gluten, currently cast as the villain in the narrative of American nutrition. Millions have blamed the put-upon protein for their digestive issues, but a recent study suggests that many people who avoid gluten may have no real health reason to do so. (That study was first published last summer, but popularized last week after a report from Real Clear Science.)

Yet many people who’ve never been diagnosed with celiac disease or a wheat allergy swear that they feel crappy when they consume gluten. So what’s going on? For some people, something called the “nocebo effect” may be at work, say the scientists who study this mind-body mystery.

The nocebo effect is sort of the “evil twin” to the more familiar placebo effect through which people experience the benefits of “drugs” that are really just sugar pills (for example), explained Dr. Morton Tavel, an internal medicine specialist at Indiana University, who has studied this response. On the flip side, if you believe something — be it a pill or a protein — will cause you physical harm, it can, even if it’s actually innocuous.

The nocebo effect has not been as well studied as the the placebo effect, but Tavel said that people’s pessimistic beliefs about a substance can be enough to trigger a psychosomatic response to it. Sometimes when doctors switch a patient from a branded drug to a pharmacologically identical generic, for example, the patient will subsequently report experiencing more negative side effects. “In well-documented cases, these effects are stronger when the media pick them up,” said Paul Enck, a professor of psychosomatic medicine at the Eberhard Karls University of Tübingen in Germany and a leading expert on the nocebo effect.

So applying this to gluten, that could mean that the protein’s nefarious image, described by prominent nutritionists in best-selling books like Wheat Belly and Grain Brain, is enough to set off a very real negative physical response in some people after they’ve consumed it (usually bloating and general digestive discomfort). “There has been a lot of negative press about the potential deleterious effects of gluten, and therefore that may induce negative brain responses when one is aware that one is eating it,” said Dr. Jon-Kar Zubieta, a University of Michigan psychiatrist who has studied the nocebo effect.

This is not to say that everyone who feels gross after eating gluten is full of it. A 2012 Mayo Clinic survey suggests that celiac disease — a small-intestine-damaging genetic disorder that is triggered as a response to eating gluten — may be underdiagnosed. Up to 1.4 of the 1.8 million Americans thought to have celiac disease may not know they do.

That same Mayo Clinic report also found that 80 percent of Americans who are following a gluten-free diet have never been diagnosed with celiac disease. And there’s evidence that the faddishness of “going gluten-free” is becoming incredibly far-reaching, as about 30 percent of people in the U.S. now say they want to cut back on gluten. This has resulted in millions of dollars for the American food industry, which reportedly made $10.5 million last year and is projected to make more than $15 billion in 2016, according to the market research company Mintel.

And these foods could actually be less healthy, overall. That’s because gluten is what gives things like bread, bagels, and other foods made from wheat and grains their sticky, stretchy qualities. Taking the gluten out oftentimes means food manufacturers need to add extra calories and fat to make, for example, gluten-free pizza crust that both tastes good and holds itself together.

Food fads come and go, and it’s certainly worth thinking them through before jumping on board. In Germany, for example, Enck says that lactose is the dietary evil du jour. “But these things shift around,” he said. “It may be gluten is coming next to us.” Gluten-free strudel, or spätzel, or pretzels? Nein, danke.