Skip to main content


Background: Bacterial probiotics are thought to exert a serotonergic effect relevant to their potential antidepressant and pro-cognitive action, but yeast probiotics have not been tested. The aim of the present study was to determine whether 30-day supplementation with Saccharomyces boulardii affects the level of salivary serotonin under psychological stress and identify the factors associated with it.

Methods: Healthy medical students were randomized to ingest Saccharomyces boulardii CNCM I-1079 or placebo before a stressful event. Salivary serotonin concentration was assessed before and at the end of supplementation. Moreover, obtained results were compared to psychological, biochemical, physiological and sociodemographic study participants data.

Results: Data of thirty-two participants (22.8 ± 1.7 years of age, 16 males) was available for the main analysis. Supplementation with Saccharomyces boulardii decreased salivary serotonin concentration under psychological stress by 3.13 (95% CI 0.20 to 6.07) ng/mL, p = 0.037, as compared to placebo. Salivary serotonin was positively correlated with salivary metanephrine (β = 0.27, 95% CI 0.02 to 0.52, p = 0.031) and pulse rate (β = 0.28, 95% CI 0.05 to 0.50, p = 0.018), but insignificantly with anxiety, depression, eating attitudes and information retrieval.

Conclusions: Saccharomyces boulardii CNCM I-1079 may be distinct from bacterial probiotics in its salivary serotonergic effect, which appears positively linked to symapathoadrenal markers. The study requires cautious interpretation, and further investigation.

Keywords: Saccharomyces boulardii; anxiety; depression; dietary supplementation; probiotic; salivary serotonin; symapathoadrenal markers; yeast.

Research Insights

SupplementHealth OutcomeEffect TypeEffect Size
Saccharomyces boulardiiReduced Salivary Serotonin Levels in Response to StressBeneficial
⬆ Back to top
Supplement Research and Comparison Website: evidence-based information about supplements, their benefits, potential risks, and their efficacy.
Receive updates about our products, services, sales, and special offers. Unsubscribe anytime. See our Privacy Policy for details on how we handle your information.

Join Our Community

Use to get in touch.