As it was a crossover study (1 week with gluten or placebo, 1 week gluten free, then 1 week with whichever they didn't have the first time), it is likely they w

As it was a crossover study (1 week with gluten or placebo, 1 week gluten free, then 1 week with whichever they didn't have the first time), it is likely they were aware that they would be receiving either gluten or a placebo (and that they would be receiving the other alternative in the next phase of the study).