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What are Psychobiotics?

“Psycho” may immediately conjure a hatchet-wielding madman and other characters of that ilk, but in the overarching health arena, this Greek word refers to “soul; mind.” Despite the rather fearsome prefix, psychobiotics are not scary –- they are a growing class of beneficial bacteria that are specialized in helping to provide critical balance of the gut-brain axis. 

Researchers in one study defined a psychobiotic as a “bacterium which when administered in adequate amounts can have a positive mental health benefit.” Researchers in another explain that this class of beneficial bacteria “exert anxiolytic and antidepressant effects characterized by changes in emotional, cognitive, systemic and neural indices. Bacteria-brain communication channels through which psychobiotics exert effects include the enteric nervous system and the immune system.”

In another study, the authors that the psychophysiological effects of psychobiotics can be grouped into three distinct categories:  Psychological effects on emotional and cognitive processes; systemic effects on the HPA axis and the glucocorticoid stress response; and inflammation which is often characterized by abnormal cytokine concentrations. 

The idea of consuming probiotics to support emotional and mental wellness may seem unusual but the field of psychobiotics is mushrooming. Researchers in one review summarized, “Indeed, although probiotic bacteria will be concentrated after ingestion, mainly in the intestinal epithelium (where they provide the host with essential nutrients and modulation of the immune system), they may also produce neuroactive substances which act on the brain-gut axis.”

Psychobiotics and the Gut-Brain-Axis

We have explored the GBA (gut-brain-axis) previously but it is worth a repeat here for context. When you feel your emotions in your gut – fear, anxiety, happiness, empathy, sadness – that’s the GBA at work, reacting physically to your emotions and thoughts. This is known as bidirectional communication between the brain and gut. And it also encompasses how emotions can alter the composition and function of the gut microbiome as well as alter the function of the GI tract. (One interesting study involved the researcher literally able to monitor stomach secretions in a volunteer and found levels coordinated with mood.

Gut–brain neural communication pathways include sympathetic and parasympathetic nerves and the enteric nervous system, all of which are  components of the autonomic nervous system – like a tree that branches, with the autonomic nervous system being the trunk.

The GBA also encompasses the vagus nerve (the longest nerve of the autonomic nervous system), which has a strong immunomodulatory role. This role may, say researchers, also have consequences for modulating brain function and mood. The authors opined, “Certainly, important advances in our understanding of the gut-brain and microbiome- gut-brain axis will come from studies of how distinct microbial and nutritional stimuli activate the vagus and the nature of the signals transmitted to the brain that leads to differential changes in the neurochemistry of the brain and behavior.”

Psychobiotics and Neurotransmitters

Gamma amino butyric acid (GABA) is the “mood amino” (an inhibitory neurotransmitter) and GABA dysregulation is implicated in depression among other mental illnesses. Researchers have been working diligently on finding gut bacteria that produce GABA. Researchers in one study of 23 individuals with depression, those with lower levels of Bacteroides exhibited more hyperactivity in their prefrontal cortex, a signifier of more intense depression. In addition, they write, “Using growth of KLE1738 as an indicator, we isolated a variety of GABA-producing bacteria, and found that Bacteroides ssp. produced large quantities of GABA.”

Strains in the Lactobacillus casei group (LCG) are being considered strongly as psychobiotics and have been the active focus of many studies in this area. In one study focusing on the brain-gut-axis the strain L. rhamnosus JB1 directly affected the expression of GABA receptors in the brain which resulted in decreased anxiety and depressive behaviors in subjects. The authors noted, “Importantly, L. rhamnosus (JB-1) reduced stress-induced corticosterone and anxiety- and depression-related behavior. “


Subjects that consumed the combination of L. plantarum 90sk and B. adolescentis 150 (strains that encourage de novo production of GABA) for two weeks exhibited reduced depressive-like behavior, in an effect similar to fluoxetine (Prozac®), said the researchers

Psychobiotics also enhance other neurotransmitters such as serotonin, dopamine and noradrenaline. For example, one study looked at the combination of Lactobacillus helveticus R0052 and Bifidobacterium longum R0175 – both are the top probiotic strains researched for effects on psychiatric health – have been shown to improve tryptophan and serotonin and reduce cortisol, thus providing mood balance.

Additionally, psychobiotics are believed to improve mood and lessen anxiety by affecting the hypothalamic-pituitary-adrenal (HPA) axis stress response in tandem with reducing systemic inflammation and by encouraging production and release of  not only neurotransmitters, but also of proteins, and short-chain fatty acids (produced in the colon by bacterial fermentation of dietary fibers and resistant starch), according to researchers.  A recent review illuminated the positive role of short-chain fatty acids in gut-brain communication. 

Human studies show the results of ingesting psychobiotics in mood-related situations. For example, in one randomized controlled trial 40 healthy male and female participants consumed either a placebo product or a probiotic blend consisting of Bifidobacterium bifidum W23, Bifidobacterium lactis W52, Lactobacillus acidophilus W37, Lactobacillus brevis W63, Lactobacillus casei W56, Lactobacillus salivarius W24, and Lactococcus lactis W19 and W58 daily for 4 weeks. The results showed that those participants in the probiotic group exhibited substantially reduced reactivity to sad mood.

Researchers of one meta-analysis of 21 meta-analyses and systematic reviews of psychobiotics in individuals with and without major depressive disorders (MDD) encompassing stress, anxiety and depression, along with related symptoms had an optimistic synopsis. They wrote, “Overall, conclusions about the effect of psychobiotics on depression-related outcomes were positive in healthy populations.” In those with clinically diagnosed MDD, they asserted, there is need for more trials.

“Nervous stomach” (cramping and diarrhea) are often linked closely to anxiety and troubled mood. It is known that probiotics can reduce symptoms of irritable bowel. Researchers evaluated the psychobiotic effects of B. longum NCC3001 on anxiety and depression in people with irritable bowel. The 10-week randomized, double-blind, placebo-controlled study of 44 adults showed that approximately 66% of those in the psychobiotic group had improvements in depression scores at week 6 and an increase in quality of life score – but no significant effect on irritable bowel symptoms. At 10 weeks, those in the psychobiotic group experienced even better depression scores.


Psychobiotics are an exciting area of probiotic supplementation for targeted self-care gains. However, if you are feeling truly depressed or have bouts of anxiety that are more frequent, visit your physician and work from there. 

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