Subjects and study design Healthy adult volunteers, aged 20-66 years, among students and employees at the Faculty of Medicine, Umeå University, Sweden were recruited to a double-blind, randomized controlled trial (RCT) through advertisements. Inclusion criteria were a self-reported healthy status and no use of antibiotics or probiotic products during 3 months prior to the study. Based on previous studies regarding the persistence of probiotic strains [31,32], the recruitment goal was at least 15 people per study group.