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Feed your microbes to deal with stress: a psychobiotic diet impacts microbial stability and perceived stress in a healthy adult population.
Berding, K, Bastiaanssen, TFS, Moloney, GM, Boscaini, S, Strain, CR, Anesi, A, Long-Smith, C, Mattivi, F, Stanton, C, Clarke, G, et al
Molecular psychiatry. 2022
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Plain language summary
Psychobiotic describe any exogenous intervention that leads to a bacterially mediated impact on the brain. Probiotics and prebiotics have shown promising results as psychobiotic agents in both animal and human studies. The aim of this study was to investigate the potential of a whole diet psychobiotic approach to modulate the microbiota composition and function, affect responses to and feelings of stress and improve mood in a healthy population. This study is a single-blind, randomized, controlled study which recruited healthy adult (male and female) participants with poor dietary habits, aged 18–59 years. Participants were block randomized (block of 4, stratified by gender) into either intervention or control group using randomly permuted blocks and were instructed to follow their respective diet for 4 weeks. Results show that a short term psychobiotic dietary intervention improved perceived stress in a healthy population, while eliciting specific metabolic changes in the gut microbiota. Authors conclude that underlying microbial influences need to be investigated and future preclinical experiments are required to explore causality and decipher mechanistic pathways.
Expert Review
Conflicts of interest:
None
Take Home Message:
Eating foods known to have a positive influence on gut microbial composition could elicit benefits in terms of reducing perceived stress and improving sleep quality.
Evidence Category:
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X
A: Meta-analyses, position-stands, randomized-controlled trials (RCTs)
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B: Systematic reviews including RCTs of limited number
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C: Non-randomized trials, observational studies, narrative reviews
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D: Case-reports, evidence-based clinical findings
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E: Opinion piece, other
Summary Review:
This RCT explored the impact of a psychobiotic diet, compared to a control diet, on perceived stress, sleep and gut microbiota.
A high psychobiotic diet is one high in prebiotic and fermented foods. In this study, a psychobiotic diet included daily recommended consumption and servings of the following:
- High prebiotic fruit & veg (6-8)
- Grains (5-8)
- Fermented foods (2-3)
- Legumes (3-4 per week)
Methodology:
- A single-blind, randomised, controlled study
- 45 healthy adults (18-59 years) with poor dietary habits
- Sample size determined by previous microbiome research - target not reached due to introduction of covid restrictrictions
- Active intervention (n=24) received dietitian advice to follow psychobitoic diet
- Control intervention (n=21) received dietitian advice largely based on the Irish Healthy Eating Guidelines food pyramid
- Intervention duration 4 weeks.
- Assessed on questionnaire measures of perceived stress and sleep, pre and post-intervention (no primary outcome defined)
- Shotgun microbiome analysis on stool samples, pre and post-intervention
Results:
- Perceived stress improved in the psychobiotic diet group
- Subjective sleep quality improved in the psychobiotic diet group
- Only subtle changes in microbial composition and function
- More stable microbiota throughout the study (regardless of diet) was correlated with greater changes in perceived stress
- Neither cortisol awakening response nor measured immune markers were affected by dietary intervention
Conclusions:
- Using a diet targeted to positively modulate gut-brain communication may have the potential for reducing stress and improving sleep
- Although improvements in stress were only observed for the intervention group – the post-intervention stress levels were not significantly different between the groups.
- Thus, we should interpret the results with some caution
Clinical practice applications:
- Providing advice on dietary intake of foods known to positively impact gut microbiota may be helpful for individuals affected by stress or sleep problems
- The inclusion of the following foods may be helpful:
- High prebiotic fruit & veg (6-8 per day)
- Grains (5-8 per day)
- Fermented foods (2-3 per day)
- Legumes (3-4 per week)
Considerations for future research:
- Important to replicate these results in a larger sample
- It might be helpful to investigate individual aspects of the diet separately, to assess their individual impact
- Objective measures of sleep (such as actigraphy recordings) might provide additionally useful findings
- It would be interesting to explore the effect of the psychobiotic diet in other conditions
- Chronobiology or chrononutrition - i.e. looking at timing of the foods proposed in the section above
Abstract
The impact of diet on the microbiota composition and the role of diet in supporting optimal mental health have received much attention in the last decade. However, whether whole dietary approaches can exert psychobiotic effects is largely understudied. Thus, we investigated the influence of a psychobiotic diet (high in prebiotic and fermented foods) on the microbial profile and function as well as on mental health outcomes in a healthy human population. Forty-five adults were randomized into either a psychobiotic (n = 24) or control (n = 21) diet for 4 weeks. Fecal microbiota composition and function was characterized using shotgun sequencing. Stress, overall health and diet were assessed using validated questionnaires. Metabolic profiling of plasma, urine and fecal samples was performed. Intervention with a psychobiotic diet resulted in reductions of perceived stress (32% in diet vs. 17% in control group), but not between groups. Similarly, biological marker of stress were not affected. Additionally, higher adherence to the diet resulted in stronger decreases in perceived stress. While the dietary intervention elicited only subtle changes in microbial composition and function, significant changes in the level of 40 specific fecal lipids and urinary tryptophan metabolites were observed. Lastly, microbial volatility was linked to greater changes in perceived stress scores in those on the psychobiotic diet. These results highlight that dietary approaches can be used to reduce perceived stress in a human cohort. Using microbiota-targeted diets to positively modulate gut-brain communication holds possibilities for the reduction of stress and stress-associated disorders, but additional research is warranted to investigate underlying mechanisms, including the role of the microbiota.
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Gut feelings: A randomised, triple-blind, placebo-controlled trial of probiotics for depressive symptoms.
Chahwan, B, Kwan, S, Isik, A, van Hemert, S, Burke, C, Roberts, L
Journal of affective disorders. 2019;253:317-326
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Plain language summary
Depression is a debilitating psychiatric disorder that is the leading cause of disability world-wide. Multiple causes of depression have been identified, including genetic, neurological, inflammatory, personality, cognitive, and environmental factors. The aim of this study was to investigate the effectiveness of the multispecies probiotic Ecologic® Barrier for reducing symptoms in adults with mild to severe levels of depression. The study was a triple-blinded parallel, placebo-controlled randomised clinical trial. Participants were randomly allocated into two groups; probiotic and placebo. 71 participants with depressive symptoms were recruited and allocated sequentially over 12 months. Results indicate that all participants across both probiotic and placebo groups exhibited a reduction in depressive symptoms over the time-period of the trial. Thus, the routine involved with daily preparation and consumption of the probiotic and scheduled appointments, as well as involvement in these behaviours with the aim of seeking improvement in depressive symptoms had positive impacts on mood, irrespective of whether the probiotic or placebo was consumed. Authors conclude that their findings offer evidence to indicate that probiotic consumption can exert change on cognitive patterns associated with depression.
Expert Review
Conflicts of interest:
None
Take Home Message:
- This study offers evidence to indicate that probiotic consumption can exert change on cognitive patterns associated with depression.
- The study suggests that probiotics, rather than having a direct effect on depressive symptoms, potentially act on immune system activity, inflammation and gut barrier integrity which contribute to the expression of depression.
- Probiotics may be a useful adjunct to potentiate the effects of other therapies, such as CBT.
- This study points to the validity of managing physical health as part of mental health treatment.
Evidence Category:
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X
A: Meta-analyses, position-stands, randomized-controlled trials (RCTs)
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B: Systematic reviews including RCTs of limited number
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C: Non-randomized trials, observational studies, narrative reviews
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D: Case-reports, evidence-based clinical findings
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E: Opinion piece, other
Summary Review:
With evidence suggesting that decreased gut barrier function and inflammation are correlated with depression, this study set out to determine the effect of consumption of probiotic supplements on depressive symptoms from a sample of 71 participants with depression. The study was a triple-blinded parallel, placebo-controlled randomised clinical trial conducted over 8 weeks in Australia. Pre and post intervention measures of symptoms and vulnerability markers of depression as well as gut microbiota were compared alongside psychological variables and gut microbiota composition to non-depressed, placebo and probiotic groups. All the clinical trial participants demonstrated an improvement in symptoms – participants in the probiotic group demonstrated a significantly greater reduction in cognitive reactivity compared with the placebo group. Probiotics did not significantly alter the microbiota of depressed individuals, however a significant correlation was found between Ruminococcus gnavus and one of the metrics for depression.
Clinical practice applications:
This study was small and carried out over a short period of time. While significant results were found, which signify potential considerations for clinical practice, the results from this study do not offer evidence that the probiotics used had a direct effect on depressive symptoms – they suggest that probiotics potentially act on cognitive processes contributing to depression which may include immune system activity, inflammation, and gut barrier integrity. Overall, this study offers evidence to indicate that probiotic consumption can exert change on cognitive patterns associated with depression. In clinical practice, probiotics may be a useful adjunct to potentiate the effects of therapies, such as CBT. Finally, the use of probiotics promotes the concept of managing physical health as part of mental health treatment.
Considerations for future research:
These preliminary results are promising and offer a number of future research and clinical avenues to build upon. The results do however, indicate that a longer trial may be needed to fully assess the effects of probiotics on mood and the mechanisms by which probiotics may be influencing this. The study also suggests that further research using a range of concentrations in a dose response study may be warranted to determine the optimal dose; a greater dose over a longer period may produce detectable changes in microbiota as well as further differences in psychological data.
Abstract
BACKGROUND Depression is the leading cause of disability worldwide; with evidence suggesting that decreased gut barrier function and inflammation are correlated with depressive symptoms. We conducted a clinical trial to determine the effect of consumption of probiotic supplements (Winclove's Ecologic® Barrier) on depressive symptoms in a sample of participants with mild to severe depression. METHOD 71 participants were randomly allocated to either probiotic or placebo, which was, consumed daily over eight weeks. Pre- and post-intervention measures of symptoms and vulnerability markers of depression as well as gut microbiota composition were compared. Clinical trial participants were also compared on psychological variables and gut microbiota composition to a non-depressed group (n = 20). RESULTS All clinical trial participants demonstrated improvement in symptoms, suggesting non-specific therapeutic effects associated with weekly monitoring visits. Participants in the probiotic group demonstrated a significantly greater reduction in cognitive reactivity compared with the placebo group, particularly in the mild/moderate subgroup. Probiotics did not significantly alter the microbiota of depressed individuals, however, a significant correlation was found between Ruminococcus gnavus and one depression metric. LIMITATIONS There was a high attrition rate, which may be attributed to weekly monitoring visits. Additionally, modulation of the gut microbiota may need more specific testing to distinguish subtle changes. CONCLUSIONS While microbiota composition was similar between all groups, probiotics did affect a psychological variable associated with susceptibility to depression. Further research is needed to investigate how probiotics can be utilised to modify mental wellbeing, and whether they can act as an adjunct to existing treatments.