The Effect of Probiotic Supplementation on Mental Health in Healthy Volunteers

Probiotics are "live microorganisms which when administered in adequate amounts confer a health benefit on the host". Accumulating evidence indicates their effect in mental health restoration. Beneficial neuropsychological and psychobiological effects are particularly well substantiated in clinical samples. However, it is not clearly documented whether probiotic supplementation reduces depressive and anxiety symptoms in healthy volunteers experiencing temporal deterioration in mental functioning while facing a stressful event. The combination of Lactobacillus helveticus R0052 and Bifidobacterium longum R0175 is particularly well studied in terms of its central nervous system action with significantly deciphered mechanism. As a result, this combination is particularly promising to study the effect of mental health improvement in healthy volunteers facing a stressful event. The aim of this project is to assess the impact of a 8-week supplementation with probiotic combination of Lactobacillus helveticus R0052 and Bifidobacterium longum R0175 strains in the daily dose of 3 × 10\^9 colony forming units on mental health measures and oral microbiota composition and metabolome in healthy young adults facing a psychologically stressful event. The aim will be achieved by comparing the probiotic combination supplement to placebo in a randomized triple-blind controlled trial settings with a participant allocation ratio of 1:1. The summer academic examination session and the upcoming first take of the final exam in pharmacology at third year of medical studies will be a model of a stressful event. The participants will supplement their diets with probiotic/placebo for 8 weeks before the exam. After giving written informed consent, before the supplementation (relatively stress-free time period in terms of academic activities) the participants will provide background sociodemographic, anthropometric and psychometric data. At that time, participants will also give samples of sali