Probiotic and placebo
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The main intervention in this trial is a dietary food supplement powder containing seven probiotic bacterial strains: lactobacillus salivarius W57, lactobacillus casei W56, lactobacillus rhamnosus W71, lactococcus lactis W58, enterococcus faecium W54, lactobacillus plantarum W62 and lactobacillus acidophilus W22 (manufactured by Winclove Probiotics B.V., Netherlands; marketed as OMNi-BiOTiC® metabolic by Institut AllergoSan GmbH, Graz, Austria) In addition, the probiotic contains 2000 IU cholecalciferol. Other ingredients are corn starch, maltodextrin, fructo-oligosaccharides, galacto-oligosaccharides, polydextrose, plant proteins, potassium chloride, magnesium sulfate, manganese sulfate and lactose. By comparison, the placebo is very similar to the probiotic visually and in taste and smell. Its ingredients are corn starch, maltodextrin, potassium chloride, magnesium sulfate and manganese sulfate. Both Verum and Placebo are packaged in blank sachets, so that patients, caregivers, investigators and outcome assessors are blinded to their content.On each sachet, the expiration date and the study acronym (ProPCO-RCT) is clearly shown. 50 sachets are packed in one box, where the instruction for ingestion, the expiration date, the randomization code and the ingredients are noted. The bacterial strains are mentioned on every box with the symbol +/- (regardless if the strains are included or not). Every participant receives 4 boxes, in total 200 sachets. An excess number of sachets (the intervention period is only 180 days) is included in case the participant loses a few.