Article - Feed your microbes to deal with stress: a psychobiotic diet impacts microbial stability and perceived stress in a healthy adult population.

Expert Review

Reviewer: Kate Lawrence

15th Dec 2022

Conflict 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

A: Meta-analyses, position-stands, randomized-controlled trials (RCTs)

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

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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.