A headline on a health blog in January 2013 offered this information to consumers:

10 Signs You're Gluten Intolerant

Along with the tips to self-diagnose, the story offered these grim “facts:”

More than 55 diseases have been linked to gluten, the protein found in wheat, rye, and barley. It’s estimated that 99% of the people who have either gluten intolerance or celiac disease are never diagnosed.

It is also estimated that as much as 15% of the US population is gluten intolerant. Could you be one of them?

If you have any of the following symptoms it could be a sign that you have gluten intolerance:

But now, questions are being raised about this condition. Peter Gibson of Monash University in Australia, who in 2011 kicked off the gluten-free trend by saying gluten-containing diets can cause gastrointestinal distress, has done a follow-up (and much more rigorous) of his 2011 study, finding (emphasis added):

“In contrast to our first study… we could find absolutely no specific response to gluten." 

Business Insiders’ Jennifer Welsh reports on Gibson’s new study, in which 37 self-identified gluten-sensitive patients were tested:

Subjects would be provided with every single meal for the duration of the trial. Any and all potential dietary triggers for gastrointestinal symptoms would be removed, including lactose (from milk products), certain preservatives like benzoates, propionate, sulfites, and nitrites, and fermentable, poorly absorbed short-chain carbohydrates, also known as FODMAPs. And last, but not least, nine days worth of urine and fecal matter would be collected. With this new study, Gibson wasn't messing around.

The subjects cycled through high-gluten, low-gluten, and no-gluten (placebo) diets, without knowing which diet plan they were on at any given time. In the end, all of the treatment diets — even the placebo diet — caused pain, bloating, nausea, and gas to a similar degree. It didn't matter if the diet contained gluten.

It seems to be a "nocebo" effect — the self-diagnosed gluten sensitive patients expected to feel worse on the study diets, so they did. They were also likely more attentive to their intestinal distress, since they had to monitor it for the study.

This study and the popularity of these health trends tells us a lot. First, scientific studies (even those that haven’t been fully tested or peer reviewed) wield tremendous power over consumers. In this case, Gibson—the author of the 2011 study—wasn’t satisfied with the findings and decided to do more rigorous testing. He has now reversed his original findings. That’s admirable and the way science should work but it also should serve as a cautionary tale about acting too quickly on the latest scientific study.

The gluten free trend also tells us a lot about the food industry. According to Welsh, the gluten-free industry is a big growth area: 30% of people want to eat less gluten and sales of gluten-free products are estimated to hit $15 billion by 2016. And although only 1% of Americans suffer from celiac disease, 18% of adults now buy gluten-free foods. Those critical of the food industry should pause to consider these numbers when they claim the food industry fails to provide people the food they demand.