Probiotics are live microorganisms exhibiting multiple properties beneficial to health. An increasing body of evidence indicates that probiotics may support healthy brain function and may relieve stress. Recent research in this area has examined lactic acid bacteria in detail, but little is known about the stress-relieving effects of Saccharomyces, a yeast with probiotic properties.

Psychological stress is a factor that allows people to successfully cope with various daily life situations. On the other hand, excessive stress may lead to bodily harm and decrease performance, e.g. academic achievements. Probiotics may help manage stress, but little is known whether probiotics improve performance under stress.

The aim of this trial is to examine whether the healthy medical students may demonstrate better performance in academic examinations when supplementing their diet with a yeast probiotic strain Saccharomyces boulardii (CNCM I-1079) or bacterial probiotic strain Lactobacillus rhamnosus GG (ATCC 53103). The secondary aim of the trial is to evaluate the potential effects of this supplementation on state anxiety as well as on biochemical and physiological stress markers.

Inclusion Criteria:

• Being a third year medical student of the Faculty of Medicine or Faculty of Military Medicine, Medical University of Lodz

Exclusion Criteria:

• formal inability to sit the first attempt of the final examination of Basic Medical Pharmacology
• chronic diseases: neurological, psychiatric, cardiological, gastroenterological, immunological, endocrine or infectious
• state of immunosuppression
• history of hospitalization (< 3 months before entrance to the study)
• presence of central venous catheter
• parenteral nutrition
• current pregnancy or intention to become pregnant within 3 months from the entrance to the study
• current lactation
• allergic reaction (< 3 months before entrance to the study)
• hypersensitivity to yeast, maltodextrins, potato starch, magnesium stearate, hypromellose, gelatin, glycerol or titanium dioxide
• body mass index over 30
• chronic medication use (current or < 3 months before entrance to the study)
• systemic antibacterial or antifungal medication use (current or < 3 months before entrance to the study)
• overuse of alcohol or psychoactive substances (current or < 3 months before entrance to the study)
• tobacco smoking - more than 5 cigarettes (or equivalents) a day (currently or < 3 months before entrance to the study)
• pro- or prebiotic preparations intake (< 3 months before entrance to the study)
• vegan or other atypical diet
• doing professional or extreme sports