Over recent years, the number of people following a gluten-free diet has more than tripled, a new study has found, though the rates of coeliac disease - which causes gluten intolerance - have remained the same.
The statistics, gathered from 22,278 people by a team from the Rutgers New Jersey Medical School, suggest that more people are dropping gluten from their diets to stay healthy or lose weight, rather than for any specific medical reason.
"People may believe a gluten-free diet is healthier, and the diet is trendy," the study's lead author, Hyunseok Kim, told Reuters.
Despite the trend, there's currently no evidence that cutting gluten out of diets has any health benefits for those without gluten intolerance (GI), the researchers say, even if individuals feel better as a result of the change.
The team looked at data collected as part of the National Health and Nutrition Examination Surveys (NHANES) in the US, finding that 0.52 percent of those without coeliac disease were following a gluten-free diet from 2009 to 2010 - a figure that jumped to 1.69 percent between 2013 and 2014.
Now about 2.7 million Americans avoid gluten in their diet, but 1.76 million have been diagnosed with coeliac disease, the study found.
The researchers say a variety of factors could be at play: public perception that going gluten-free is healthier, gluten-free products becoming more widely available and less expensive, and people self-diagnosing gluten sensitivity.
Oddly enough, the fact that more of us are ready to give up gluten might have actually helped to prevent cases of coeliac disease from rising, the study suggests, though for now, we can't be sure.
While giving up gluten could improve certain people's health, it might not necessarily be because of the sudden lack of gluten, points out a commentary published alongside the new research.
"It is important for clinicians to understand whether, in most cases, it is the elimination of the protein gluten that is responsible for symptom improvement or whether following a gluten-free diet is simply a marker of other dietary choices that are creating positive effects," writes Daphne Miller, from the University of California, who wasn't involved in the research.
The lack of grain and processed food in a gluten-free diet could also explain why people who switch to it start to feel better, Miller suggests.
In other words, the reason your new gluten-free diet is making you feel better isn't necessarily anything to do with the gluten.
The study follows research carried out last year that found no evidence of gluten sensitivity in those without coeliac disease.
When 37 self-identified gluten-sensitive patients ate high-gluten, low-gluten, and no-gluten (placebo) diets, without knowing which diet plan they were on, they experienced pain, bloating, nausea, and gas to a similar degree - it didn't matter if the diet contained gluten.
"[The researchers] put their results down to the 'nocebo effect' - the anxiety felt by someone who thinks they're at risk of getting sick can sometimes actually make them feel sick - or perhaps the presence of carbohydrates called FODMAPS that some people could find hard to digest. But as far as gluten is concerned, it doesn't appear to be the menace we've been making it out to be."
The Rutgers team now plans on getting to the bottom of this by expanding their study to include a wider sample of people, because it seems like we don't have to be allergic to something to be negatively affected by it.
"Researchers and clinicians can use this as an opportunity to understand how factors associated with this diet affect a variety of symptoms, including gastrointestinal function, cognition, and overall well-being," says Miller.
The study has been published in JAMA Internal Medicine.