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

Measuring wellbeing: A scoping review of metrics and studies measuring medical student wellbeing across multiple timepoints

PURPOSE

Studies have demonstrated poor mental health in medical students. However, there is wide variation in study design and metric use, impairing comparability. The authors aimed to examine the metrics and methods used to measure medical student wellbeing across multiple timepoints and identify where guidance is necessary.

METHODS

Five databases were searched between May and June 2021 for studies using survey-based metrics among medical students at multiple timepoints. Screening and data extraction were done independently by two reviewers. Data regarding the manuscript, methodology, and metrics were analyzed.

RESULTS

221 studies were included, with 109 observational and 112 interventional studies. There were limited studies (15.4%) focused on clinical students. Stress management interventions were the most common (40.2%). Few (3.57%) interventional studies followed participants longer than 12 months, and 38.4% had no control group. There were 140 unique metrics measuring 13 constructs. 52.1% of metrics were used only once.

CONCLUSIONS

Unique guidance is needed to address gaps in study design as well as unique challenges surrounding medical student wellbeing surveys. Metric use is highly variable and future research is necessary to identify metrics specifically validated in medical student samples that reflect the diversity of today's students.

Personality traits and health-related behaviors in medical students facing a stressful event

Background

It is believed that personality traits have an impact on the propensity to change and maintain favorable lifestyle habits. This issue has been raised by multiple studies, however, none of them appeared to focus on population under severe psychological stress. The aim of the present study was to investigate the link between personality traits and health-related behaviors and measures such as dietary intake of specific food products, physical activity, body-mass index and the use of cigarettes in medical students facing a stressful event.

Methods

The study included a cohort of third-year medical students from the Medical University of Lodz, Poland, facing a stressful subject exam during the first COVID-19-related lockdown. At baseline, personality traits were evaluated with the use of the Polish version of the Big Five Inventory-Short questionnaire. Then, consumption of selected food products was monitored with the use of seven-day electronic dietary record. Also, some other health-related data was collected (body-mass index, physical activity and the use of cigarettes). General Linear Modeling techniques, logistic regression and exploratory factor analysis were applied to analyze the data.

Results

Four hundred and forty-four students completed the study. A two-factor pattern of food consumption was discovered by the exploratory factor analysis in the study group (34% of the variance explained). Higher conscientiousness, but not the other personality traits, was found to be significantly associated with generally healthier lifestyle manifested by higher consumption of vegetables, wholegrain products, fruits and nuts (adjusted beta 0.16, 95%CI 0.06 to 0.26, pη2 = 2.3%, p = 0.0015) and lower cigarette smoking (adjusted odds ratio 0.84, 95%CI 0.75 to 0.94, p = 0.0020), but insignificantly with physical activity and body-mass index.

Conclusion

Severely stressed medical students expressing high conscientiousness tend to present healthier behaviors. Therefore, interventions aimed at improving lifestyle habits in students with low conscientiousness might be useful.

Anorexia nervosa and gut microbiome: implications for weight change and novel treatments

INTRODUCTION

Host-microbiota interactions may be involved in many physical and psychological functions ranging from the digestion of food, maintenance of immune homeostasis, to the regulation of mood and cognition. Microbiome dysbiosis has been consistently described in many diseases. The pathogenesis and weight regulation mechanism in anorexia nervosa (AN) also seem to be implicated in the dynamic bidirectional adjustment of the microbiota-gut-brain axis. This review aims at elucidating this relationship.

AREA COVERED

This review starts with a description of pathogenic gut-brain pathways. Next, we focus on the latest research on the associations between gut microbiota and weight change in the condition of AN. The strategies to alter the intestinal microbiome for the treatment of this disorder are discussed, including dietary, probiotics, prebiotics, synbiotics, and fecal microbiota transplantation.

EXPERT OPINION

Gut microbiome is inextricably linked to AN. It may regulate weight gain in the process of refeeding via the microbiota-gut-brain axis, while the specific mechanism has yet to be clearly established. In the future, a better understanding of gut microbiome could have implications for developing microbiome-based prevention, diagnostics and therapies.

Effect of Probiotics Supplementation on Heart Rate: A Systematic Review and Meta-Analysis of Randomized Clinical Trials

Background and Aims

Probiotics consumption lowers the risk of cardiovascular disease, but whether it affects heart rate (HR) remains controversial. Therefore, our study aimed to assess the chronotropic effects of probiotics on heartbeat via a meta-analysis of randomized clinical trials.

Methods

Relevant studies were identified by searching PubMed, Cochrane library, and Clinical Trials databases up to October 2021. Either a fixed-effects or a random-effects model was used to calculate the pooled effect sizes and 95% confidence intervals (CIs).

Results

This meta-analysis included 13 studies involving 16 interventional trial arms and 931 participants according to inclusion criteria. The overall pooled estimate showed that probiotics supplementation had a slight, but no significant reduction of 0.28 bpm (95% CI: −1.17, 0.60) on HR. Relatively high heterogeneity was observed among included trials (I² = 80.8%, P heterogeneity < 0.001). Subgroup analysis displayed that probiotics supplementation significantly reduced HR by 2.94 bpm (95% CI: −5.06, −0.82) among participants with baseline HR ≥ 75 bpm, by 1.17 bpm (95% CI: −2.34, −0.00) with probiotics dose ≥1 × 10¹⁰ CFU/day, and by 1.43 bpm (95% CI: −2.69, −0.17) with multiple-strain intervention. Meta-regression analysis showed that baseline HR was a major potential effect modifier of probiotics supplementation on lowering HR.

Conclusion

Hitherto, the overall evidence in the literature was insufficient to support the notion that probiotics supplementation has a class effect on HR reduction. However, in subgroup analysis, probiotics reduced HR significantly in those who had higher baseline HR, received a higher dose or multiple strains of probiotics.

Best Practices for Probiotic Research in Athletic and Physically Active Populations: Guidance for Future Randomized Controlled Trials

Probiotic supplementation, traditionally used for the prevention or treatment of a variety of disease indications, is now recognized in a variety of population groups including athletes and those physically active for improving general health and performance. However, experimental and clinical trials with probiotics commonly suffer from design flaws and different outcome measures, making comparison and synthesis of conclusions difficult. Here we review current randomized controlled trials (RCTs) using probiotics for performance improvement, prevention of common illnesses, or general health, in a specific target population (athletes and those physically active). Future RCTs should address the key elements of (1) properly defining and characterizing a probiotic intervention, (2) study design factors, (3) study population characteristics, and (4) outcome measures, that will allow valid conclusions to be drawn. Careful evaluation and implementation of these elements should yield improved trials, which will better facilitate the generation of evidence-based probiotic supplementation recommendations for athletes and physically active individuals.

Association Between Consumption of Fermented Food and Food-Derived Prebiotics With Cognitive Performance, Depressive, and Anxiety Symptoms in Psychiatrically Healthy Medical Students Under Psychological Stress: A Prospective Cohort Study

Background

Gut microbiota-based therapeutic strategies, such as probiotic and prebiotic preparations, may benefit mental health. However, commonly consumed fermented and prebiotic-containing foods have not been well-tested. The aim of the present study was to determine whether consumption of fermented food and food-derived prebiotics is associated with cognitive performance, depressive, and anxiety symptoms in psychiatrically healthy medical students under psychological stress.

Methods

The study protocol with data analysis plan was prospectively registered. Food consumption was evaluated with a 7-day dietary record. Cognitive performance was modeled with academic examination performance in relation to subject knowledge. Pre-exam depressive and anxiety symptoms were assessed with the Patient Health Questionnaire-9 and Generalized Anxiety Disorder-7, respectively.

Results

In total, 372 medical students (22.7 ± 1.1 years of age, 66% female) completed the study. No relationship was observed between cognitive performance under stress and either fermented food (adjusted β 0.02, 95% CI −0.07–0.11, p = 0.63) or food-derived prebiotics consumption (adjusted β −0.00, 95% CI −0.09–0.09, p = 0.99). High intake of fermented food was associated with more severe depressive (adjusted β 0.11, 95% CI 0.01–0.20, p = 0.032) and anxiety symptoms under stress (adjusted β 0.13, 95% CI 0.04–0.22, p = 0.0065); however, no such link was observed for food-derived prebiotics (adjusted β 0.03, 95% CI −0.07–0.13, p = 0.50 and −0.01, 95% CI −0.11–0.08, p = 0.83, for depression and anxiety, respectively).

Conclusions

Under psychological stress in medical students, consumption of fermented food and food-derived prebiotics appears to be not associated with cognitive performance. High intake of fermented food, but not food-derived prebiotics, may be associated with severity of depressive and anxiety symptoms. The safety of fermented food in this regard therefore requires further clarification.

A Systematic Review of Psychobiotic Interventions in Children and Adolescents to Enhance Cognitive Functioning and Emotional Behavior

This systematic review brings together human psychobiotic interventions in children and adolescents (aged 6-25 years) to evaluate the efficacy of pre- and probiotic supplements on stress, anxiety, and cognitive outcomes. Psychobiotic interventions in animal studies highlighted sensitivity to effects during development and maturation in multiple domains from emotion to cognitive processing. Several translational psychobiotic interventions in humans have been carried out to assess effects on emotion and cognition during childhood and into adulthood. The findings illustrate that there are limited consistent psychobiotic effects in developing human populations, and this is proposed to be due to heterogeneity in the trials conducted. Consequentially, it is recommended that three specific factors are considered in future psychobiotic trials: (1) Specificity of population studied (e.g., patients, developmental age), (2) specificity of intervention, and (3) homogeneity in outcome measures.

Effect of Probiotics on Psychiatric Symptoms and Central Nervous System Functions in Human Health and Disease: A Systematic Review and Meta-Analysis

Background: The gut microbiota impacts on central nervous system (CNS) function via the microbiota–gut–brain axis. Thus, therapeutics targeting the gut microbiota such as probiotics have the potential for improving mental health. This meta-analysis synthesizes the evidence regarding the impacts of probiotics on psychological well-being, psychiatric symptoms and CNS functioning. Methods: The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were applied for executing this review using the databases PubMed, Web of Science and Cochrane Library. The data were summarized at qualitative and quantitative level. Results: Fifty-four randomized placebo-controlled studies were included, of which 30 were eligible for meta-analysis. If investigated, the probiotics mostly exerted effects on CNS function. Most probiotics did not affect mood, stress, anxiety, depression and psychiatric distress when compared to placebo at the qualitative level. At quantitative level, depression and psychiatric distress improved slightly in the probiotic condition (depression: mean difference −0.37 (95% CI: −0.55, −0.20); p ≤ 0.0001; psychiatric distress: mean difference −0.33 (95% CI: −0.53, −0.13); p = 0.001). Conclusions: To date it is unclear to which extent and in which specific areas next generation probiotics selected and developed for their ability to improve psychiatric condition and potentially other CNS functions are promising.

Mechanisms of Cognitive Impairment in Depression. May Probiotics Help?

Depression is the major cause of disability globally. Apart from lowered mood and accompanying symptoms, it leads to cognitive impairment that altogether predicts disadvantaged social functioning. Reduced cognitive function in depression appears a bit neglected in the field of clinical and molecular psychiatry, while it is estimated to occur in two-thirds of depressed patients and persist in at least one third of remitted patients. This problem, therefore, requires elucidation at the biomolecular and system levels and calls for improvement in therapeutic approach. In this review study, we address the above-mentioned issues by discussing putative mechanisms of cognitive decline in depression: (1) increased oxidative stress and (2) inflammation, (3) disturbed hypothalamus-pituitary-adrenals axis, and (4) reduced monoamines functionality. Moreover, we acknowledge additional underpinnings of cognitive impairment in depressed elderly: (5) vascular-originated brain ischemia and (6) amyloid-beta plaque accumulation. Additionally, by reviewing molecular, pre-clinical and clinical evidence, we propose gut microbiota-targeted strategies as potential adjuvant therapeutics. The study provides a consolidated source of knowledge regarding mechanisms of cognitive impairment in depression and may path the way toward improved treatment options.

The role of microbiota-gut-brain axis in neuropsychiatric and neurological disorders

Emerging evidence indicates that the gut microbiota play a crucial role in the bidirectional communication between the gut and the brain suggesting that the gut microbes may shape neural development, modulate neurotransmission and affect behavior, and thereby contribute to the pathogenesis and/or progression of many neurodevelopmental, neuropsychiatric, and neurological conditions. This review summarizes recent data on the role of microbiota-gut-brain axis in the pathophysiology of neuropsychiatric and neurological disorders including depression, anxiety, schizophrenia, autism spectrum disorders, Parkinson's disease, migraine, and epilepsy. Also, the involvement of microbiota in gut disorders co-existing with neuropsychiatric conditions is highlighted. We discuss data from both in vivo preclinical experiments and clinical reports including: (1) studies in germ-free animals, (2) studies exploring the gut microbiota composition in animal models of diseases or in humans, (3) studies evaluating the effects of probiotic, prebiotic or antibiotic treatment as well as (4) the effects of fecal microbiota transplantation.

Psychobiotic interventions for anxiety in young people: a systematic review and meta-analysis, with youth consultation

The human gut microbiome influence on brain function and mental health is an emerging area of intensive research. Animal and human research indicates adolescence as a sensitive period when the gut-brain axis is fine-tuned, where dietary interventions to change the microbiome may have long-lasting consequences for mental health. This study reports a systematic review and meta-analysis of microbiota-targeted (psychobiotics) interventions on anxiety in youth, with discussion of a consultation on the acceptability of psychobiotic interventions for mental health management amongst youth with lived experience. Six databases were searched for controlled trials in human samples (age range: 10-24 years) seeking to reduce anxiety. Post intervention outcomes were extracted as standard mean differences (SMDs) and pooled based on a random-effects model. 5416 studies were identified: 14 eligible for systematic review and 10 eligible for meta-analysis (total of 324 experimental and 293 control subjects). The meta-analysis found heterogeneity I² was 12% and the pooled SMD was -0.03 (95% CI: -0.21, 0.14), indicating an absence of effect. One study presented with low bias risk, 5 with high, and 4 with uncertain risk. Accounting for risk, sensitivities analysis revealed a SMD of -0.16 (95% CI: -0.38, 0.07), indicative of minimal efficacy of psychobiotics for anxiety treatment in humans. There is currently limited evidence for use of psychobiotics to treat anxiety in youth. However, future progress will require a multidisciplinary research approach, which gives priority to specifying mechanisms in the human models, providing causal understanding, and addressing the wider context, and would be welcomed by anxious youths.

Decrease in Salivary Serotonin in Response to Probiotic Supplementation With Saccharomyces boulardii in Healthy Volunteers Under Psychological Stress: Secondary Analysis of a Randomized, Double-Blind, Placebo-Controlled Trial

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.