Each Centre will enroll 20 patients with suspected nonceliac gluten sensitivity and 20 healthy volunteers. Recruitment of patients and, at greater extent, healthy volunteers should not be an issue as the 21 Centres involved in this trial are well-known for diagnosis and treatment of gluten-related disorders. The Investigators will consider drop-outs from the study all the patients who will fail to attend even a single appointment or test in the trial. Moreover, compliance with the study treatment will be assessed by unused capsule counts at T2 and T4. Compliance with the gluten-free diet at each time point will be assessed through a validated questionnaire. To exclude the possibility of patients being able to discriminate between gluten capsules and placebo capsules, we preliminarily tested capsule recognition in a group of 20 healthy volunteers. On two different days, healthy volunteers were asked to take capsules and then clearly state if the capsules contained gluten or not. Healthy volunteers were not able to differentiate the appearance and taste of gluten capsules from those of placebo capsules. Assuming a within-patient comparison and a SD of the overall score of 40, 70 subjects per arm would be needed in order to achieve a power of 80%, at a 2-sided 5% significance level, if the true difference is 15.