2.2. Data Collection

The first five participants from the control group and the first five participants from the experimental group that finalized the GRAIN study were asked by the project group to participate in an individual interview. They were interviewed by the first author (a professor in health and nutrition communication) after the intervention (from October 2021 to January 2022). Five of the participants in this qualitative study were in the experimental group. The other five participants were in the control group receiving benchmark bread and corn flakes. The interviews adhered to a semi-structured interview guide developed by the multi-professional project group. The main themes in the interview guide were: (1) experiences with a gluten-free diet; (2) experiences with the products in the GRAIN-study; (3) experiences with participating in the GRAIN-study. The interview guide is attached as Supplementary Materials File S1. The first author pilot-tested the interview guide. The pilot test interview was included in the analysis, as only minor adjustments were made in the interview guide. The first author was not involved in the recruitment process and did not have any personal relationships with the participants prior to the study. The interviews lasted between 14 and 33 min and were conducted via Zoom. The recruitment process was conducted until we had achieved sufficient informational power, depending upon the quality of the interviews and the aim of the study [24]. We followed the consolidated criteria for reporting qualitative studies (COREQ) [25].