Effect of Supplementation with Saccharomyces Boulardii on Academic Examination Performance and Related Stress in Healthy Medical Students: A Randomized, Double-Blind, Placebo-Controlled Trial

Michał Seweryn Karbownik, Joanna Kręczyńska, Paulina Kwarta, Magdalena Cybula, Anna Wiktorowska-Owczarek, Edward Kowalczyk, Tadeusz Pietras, Janusz Szemraj, Michał Seweryn Karbownik, Joanna Kręczyńska, Paulina Kwarta, Magdalena Cybula, Anna Wiktorowska-Owczarek, Edward Kowalczyk, Tadeusz Pietras, Janusz Szemraj

Abstract

In recent years, bacterial probiotic dietary supplementation has emerged as a promising way to improve cognition and to alleviate stress and anxiety; however, yeast probiotics have not been tested. The aim of the present study was to determine whether 30-day supplementation with Saccharomyces boulardii enhances academic performance under stress and affects stress markers. The trial was retrospectively registered at clinicaltrials.gov (NCT03427515). Healthy medical students were randomized to supplement their diet with Saccharomyces boulardii CNCM I-1079 or placebo before sitting for an academic examination, which served as a model of stress. The grades of a final examination adjusted to subject knowledge tested in non-stressful conditions was used as a primary outcome measure. Psychometrically evaluated state anxiety, cortisol and metanephrine salivary levels, and pulse rate were tested at a non-stressful time point before the intervention as well as just before the stressor. Fifty enrolled participants (22.6 ± 1.4 years of age, 19 males) completed the trial in the Saccharomyces and placebo arms. Supplementation with Saccharomyces did not significantly modify examination performance or increase in state anxiety, salivary cortisol, and metanephrine. However, the intervention resulted in higher increase in pulse rate under stress as compared to placebo by 10.4 (95% CI 4.2-16.6) min-1 (p = 0.0018), and the effect positively correlated with increase in salivary metanephrine (Pearson's r = 0.35, 95% CI 0.09-0.58, p = 0.012). An intention-to-treat analysis was in line with the per-protocol one. In conclusion, supplementation with Saccharomyces boulardii CNCM I-1079 appears largely ineffective in improving academic performance under stress and in alleviating some stress markers, but it seems to increase pulse rate under stress, which may hypothetically reflect enhanced sympathoadrenal activity.

Keywords: Saccharomyces boulardii; academic examination; anxiety; dietary supplementation; probiotic; pulse rate; salivary cortisol; salivary metanephrine; stress.

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Timeline of the study procedures.
Figure 2
Figure 2
Study flow diagram.
Figure 3
Figure 3
Primary outcome measure: final examination scores. A per protocol analysis is presented. Individual data points are marked. The mean scores are represented by horizontal lines. The effect sizes of the difference in the scores together with a p-value for the comparison are reported above the graph. The analysis is presented after adjusting for the results of the preexamination test in pharmacology held a day before the final examination.
Figure 4
Figure 4
Secondary outcome measures: Individual data points are marked and linked with a grey line between “basal” and “preexamination” time points. The mean scores are represented by horizontal lines for both “basal” and “preexamination” settings. The effect size of the differences between the increase in the measures together with p-values for the comparisons are reported above the graph. (A) The extent of increase in state anxiety between the study groups. (B) The extent of increase in salivary cortisol level between the study groups. (C) The extent of increase in salivary metanephrine level between the study groups. (D) The extent of increase in pulse rate between the study groups.

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