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. (Read more about the study.)
"In contrast to our first study… we could find absolutely no specific response to gluten," Gibson wrote in the paper. A third, larger study published this month has confirmed the findings.
It should be noted that this study is not about celiac disease — what it's saying is that if you don't have that specific disease you can eat all the gluten you want.