Psychobiotics are helpful bacteria (probiotics) or support for these bacteria (prebiotics) that influence the relationship between bacteria and brain. The human digestive system houses around 100 trillion of these bacteria, outnumbering the human body cells 10:1. Probiotics provide a great deal of functions vital to our well-being, like supporting the digestion process and improving the absorption of nutrients. Based on the latest research, helpful gut bacteria that can also positively affect the brain – psychobiotics – benefit people suffering from chronic stress, poor mood, or anxiety-like symptoms (1).

There are 3 ways psychobiotics can affect your mental health:

  • Brain chemicals like serotonin, dopamine, and noradrenaline can be produced in the intestines directly by gut microbiota.
  • Battling with and protecting from stress by modifying the level of stress hormones.
  • When an inflammation occurs, inflammatory agents are elevated throughout the body and brain and can cause depression and other mood and cognitive disorders. Psychobiotics can affect the brain by lowering inflammation.

Lactobacillus and Bifidobacterium are the most popular probiotics with respect to mental health (1).

Disruption of the balance of gut bacteria is quite common due to the use of different kinds of medications, antibiotics, artificial preservatives, poor food and water quality, herbicides, stress, and infections (2, 3, 4).

In order to support a healthy microbiota, one should start from eating a diverse range of foods rich in different plant sources. Foods that contain lots of fiber or are fermented also promote the growth of beneficial gut bacteria. Excessive consumption of sugar and artificial sweeteners should be minimized. Managing stress levels, exercising on a regular basis, not smoking and getting enough sleep are also important for keeping microbiota in good condition. When taking antibiotics, one should make sure to consume probiotics so the body can maintain the bacteria it needs to stay healthy.

For people needing help regarding mental health problems, psychobiotics may be a promising relief. Psychobiotics are well-adapted to the intestinal environment and naturally modulate gut–brain axis communications, thereby reducing the chance of adverse reactions.

It is possible that even simple prescribing of a particular diet may be sufficient to promote the selective proliferation of natural or therapeutically introduced psychobiotics (5). Further research focusing on the strain and dosage of psychobiotics, duration of treatment, and the nature of mental disorders will help to determine the most efficient ways of helping people to improve their mental health.

REFERENCES
Abhari A, Hosseini H (2018) Psychobiotics: Next generation treatment for mental disorders? J Clin Nutr Diet. 4:1. doi:10.4172/2472-1921.100063

Carding et al (2015) Dysbiosis of the gut microbiota in disease. Microb Ecol Health Dis. 26: 10.3402/mehd.v26.26191

Lozano et al (2018) Sex-dependent impact of Roundup on the rat gut microbiome. Toxicol Rep. 5:96–107. doi: 10.1016/j.toxrep.2017.12.005

Paula Neto et al (2017) Effects of food additives on immune cells as contributors to body weight gain and immune-mediated metabolic dysregulation. Front Immunol. 8:1478. doi:10.3389/fimmu.2017.01478

Kali (2016) Psychobiotics: An emerging probiotic in psychiatric practice. Biomed J. 39(3):223-224. doi:10.1016/j.bj.2015.11.004

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A hot topic these days, that one can hear more and more information about is the microbiota-gut-brain axis, the bidirectional interaction between the intestinal microbiota and the central nervous system nowadays, this has become a hot topic. We are becoming increasingly aware that gut microbiota play a significant role in modulating brain functions, behavior and brain development. Pre- and probiotics can influence the microbiota composition, so the question arises, can we have an impact on our mental health by controlling nutrition and using probiotics?

Burokas and colleagues aimed to investigate this possibility in their study (2017), where the goal was to test whether chronic prebiotic treatment in mice modifies behavior across domains relevant to anxiety, depression, cognition, stress response, and social behavior.

In the first part of the study, the researchers fed mice with prebiotics for 10 weeks. They were administered the prebiotics fructo-oligosaccharides (FOS), galacto-oligosaccharides (GOS), a combination of both, or water. FOS and GOS are soluble fibers that are associated with the stimulation of beneficial bacteria such as bifidobacterium and lactobacillus.

Behavioral testing started from the third week including

  • the open field test (anxiety – amount of exploratory behavior in a new place),
  • novel object test (memory and learning – exploration time of a novel object in a familiar context), and
  • forced swimming test (depression-like behavior – amount of activity in the cylinder filled water).

Meanwhile, plasma corticosterone, gut microbiota composition, and cecal short-chain fatty acids were measured. Taken together, the authors found that the prebiotic FOS+GOS treatment exhibited both antidepressant and anxiolytic (anti-anxiety) effects. However, there were no major effects observed on cognition, nociception (response to pain stimulus), and sociability; with the exception of blunted aggressive behavior and more prosocial approaches.

In the second part, FOS+GOS or water-treated mice were exposed to chronic psychosocial stress. Behavior, immune, and microbiota parameters were assessed. Under stress, the microbiota composition of water-treated mice changed (decreased concentration of bifidobacterium and lactobacillus), which effect was reversed by treatment with prebiotics.

Furthermore, it was found that three weeks of chronic social stress significantly reduced social interaction, and increased stress indicators (basal corticosterone levels and stress-induced hyperthermia), whereas prebiotic administration protected from these effects.

After stimulation with a T-cell activator lectin (concanavalin A), the stressed, water-treated mice group presented increased levels of inflammatory cytokines (interleukin 6, tumor necrosis factor alpha), whereas in animals with prebiotics had these at normal levels.

Overall, these results suggest a beneficial role of prebiotic treatment in mice for stress-related behaviors and supporting the theory that modifying the intestinal microbiota via prebiotics represents a promising potential for supplement therapy in psychiatric disorders.

Watch YouTube Video:
https://youtu.be/E479yto8pyk

REFERENCES
Burokas, A., Arboleya, S., Moloney, R. D., Peterson, V. L., Murphy, K., Clarke, G., Stanton, C., Dinan, T. G., & Cryan, J. F. (2017). Targeting the Microbiota-Gut-Brain Axis: Prebiotics Have Anxiolytic and Antidepressant-like Effects and Reverse the Impact of Chronic Stress in Mice. Biological Psychiatry, 82(7), 472–487. https://doi.org/10.1016/j.biopsych.2016.12.031

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Recently, the idea that gastrointestinal microbiota are able to affect host behaviour is gaining momentum and it is based on studies conducted with animal models but also in humans with neurological disorders. However, the mechanisms that underlay this complex interplay between gut, brain and microbiota are not completely understood. Here we discuss recent findings on how microbial products could potentially affect the gut-brain axis.

Intestinal microbiota grow through the fermentation of undigested carbohydrates that end up in the large intestine. It was shown that absence of microbes or disruption of the microbiota, led to increased populations of impaired microglia cells in mice. Microglia cells are the primary effector cells for immune signalling to the central nervous system. The presence of a complex microbiota community, was shown to be essential for proper microglia maturation and function [1].

The main products of microbial fermentation in the gut are; acetate, propionate and butyrate, collectively known as short chain fatty acids(SCFA’s). Their beneficial role in human physiology have been well described, and recently evidence suggests that these molecules are able to cross blood brain barrier [2]. Moreover, gut microbiota have been associated with the brain barrier integrity. Mice raised in absence of bacteria are reported to have reduced brain barrier integrity. Once colonized with either a butyrate or an acetate/propionate producing bacteria, significant improvements were reported in the barrier [3]. Notably the integrity of the blood-brain barrier from the germ free mice was able to be restored through the oral administration of butyrate.

Gut_Microbes and Mental HealthSCFA’s are among the molecules having the privilege to cross the blood brain barrier and access the brain directly, their role should be studied in detail.

Recent studies also demonstrate that gut microbes regulate levels of intestinal neurotransmitters. The enteric nervous system interacts with a plethora of neurotransmitters (more than 30 have been identified so far.) Actually, the bulk of serotonin production ~90%, a neurotransmitter associated with mood and appetite is located in the gut. Specialized cells known as enterochromaffin cells are the main serotonin producers in the gut. In the absence of intestinal microbiota gastrointestinal serotonin levels are depleted. However, they can be restored by the addition of a specific spore forming consortium of intestinal bacteria. Specific bacterial metabolites have been reported to mediate this effect [4].

Other intestinal microbiota have been reported also to regulate the levels of the GABA neurotransmitter. Reduced levels of GABA have been associated with anxiety, panic disorder and depression. Bacterial GABA producers have been known to exist for years but it was not until 2016 that a gut bacteria was identified as GABA consumer [5]. For example, decreased levels of bacterial GABA producers were identified in a human cohort of depressed individuals. Studies in mice reinforce these findings. Intervention with the lactic acid bacteria Lactobacillus rhamnosus (JB-1) in healthy mice reduced anxiety related symptoms (accompanied by a reduction in the mRNA expression of GABA receptors in the Central Nervous System.) Lactic acid producing bacteria have also been reported to produce GABA in several food products such as kimchi, fermented fish and cheese [6].

Collectively, our gut microbiota encodes for ~100 times more genes than the human genome. The potential for some of these microbial genes to produce compounds able to interact with the nervous system and regulate critical pathways implicated in the gut brain axis is realistic and worth being explored.

Authors Prokopis Konstanti, MSc and Clara Belzer, PhD are working in the Department of Molecular Ecology, Laboratory of Microbiology, Wageningen University, Netherlands.

Footnotes

  1. Erny, D., et al., Host microbiota constantly control maturation and function of microglia in the CNS. Nature neuroscience, 2015. 18(7): p. 965-977.
  2. Joseph, J., et al., Modified Mediterranean Diet for Enrichment of Short Chain Fatty Acids: Potential Adjunctive Therapeutic to Target Immune and Metabolic Dysfunction in Schizophrenia? Frontiers in Neuroscience, 2017. 11(155).
  3. Braniste, V., et al., The gut microbiota influences blood-brain barrier permeability in mice. Science translational medicine, 2014. 6(263): p. 263ra158-263ra158.
  4. Yano, J.M., et al., Indigenous bacteria from the gut microbiota regulate host serotonin biosynthesis. Cell, 2015. 161(2): p. 264-276.
  5. P. Strandwitz, K.K., D. Dietrich, D. McDonald, T. Ramadhar, E. J. Stewart, R. Knight, J. Clardy, K. Lewis; , Gaba Modulating Bacteria of the Human Gut Microbiome. 2016.
  6. Dhakal, R., V.K. Bajpai, and K.-H. Baek, Production of gaba (γ – Aminobutyric acid) by microorganisms: a review. Brazilian Journal of Microbiology, 2012. 43(4): p. 1230-1241.

 

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