2.1. Recruitment, Blinding and Randomization
bloating, allergic, allergy, headache
RECRUITMENT, ALLERGY, POLAND
Trial subjects consisted of full-time students attending courses at Pomeranian Medical University in Szczecin, Poland. The only exclusion criterium was having an allergy to cow’s milk. The general health status of all participants was considered good and made them eligible for studying full time at the university, which was confirmed by obligatory periodic medical check-ups.The trial was administered by a dedicated person, an administrator, who controlled the enrolment process and collection of formal consent forms, performed blinding and randomization process of participants, and finally, maintained the database. In the present study participants, recruiters and the study manager were blinded to allocation. The administrator was also the only person to contact participants by e-mail and to provide them with links to all the on-line survey forms (initial as well as daily/weekly surveys). These questionnaires were provided to participants based on the EUSurvey system, a free of charge, official online survey management tool launched in 2013 by the European Commission [The recruitment of each participant was preceded by the detailed explanation of study principals in verbal as well as written form. Upon acquiring the formal consent forms, 271 students were recruited to the study. Of those originally enrolled, 9 participants dropped out due to suspecting being allergic to milk, 10 resigned without stating the reason and an additional 18 failed to respond to any or all of the entry level on-line surveys. Finally, 234 participants qualified to enter the study in the fall of 2021. They were blinded by associating them with individual trial ID numbers, which from this point were the only attribute used to identify the participants. Subsequently, they were stratified by attendance to certain study groups and randomly assigned to supplementation groups (with the use of MS Excel Random Sort tool). Finally, all participants began supplementation upon the signal given by the administrator. During the first three weeks of the trial, an additional 7 participants informed us about their resignation from further participation stating various, usually personal, reasons. Just two participants, both from placebo group, decided on resignation due to observing supposed side effects of the supplementation—bloating and headache.