Psychobiotics are a class of pre- and probiotics that produce neuroactive substances.
These substances have a tremendous effect on the brain‑gut communication axis.
There are many strains of psychobiotic bacteria.
What are psychobiotics?
Psychobiotics refer to probiotics and even some prebiotics that are able to produce neuroactive substances that have a positive effect on our CNS (central nervous system). The bidirectional signalling between the gut microbiota and the brain takes place through neuronal pathways that involve both the central and enteric nervous systems as well as the circulatory system. The latter includes the hypothalamus‑pituitary‑adrenal axis, immune regulators, hormones and bacterial metabolites, which include neurotransmitters.
Specifically, the term 'psychobiotic' is understood as a living organism that, when taken in adequate amounts, provides mental health benefits to many patients suffering from psychiatric illness. It is a class of probiotics where these bacteria are capable of producing and delivering neuroactive substances such as gamma‑aminobutyric acid (GABA) and serotonin. These substances have a significant impact on the communication axis between the brain and the gut. Some psychobiotics have been found to have antidepressant or anxiolytic effects. To date, psychobiotics have most often been studied in the psychiatric setting in patients with irritable bowel syndrome, where positive benefits have been reported for a number of organisms.
Strains of psychobiotics
Lactobacillus plantarum: Significantly reduces anxiety and increases quality of life by increasing dopamine and serotonin levels, lowering stress hormones and reducing inflammation when taken regularly. It is commonly found in many fermented vegetables, including sauerkraut, pickles, olives and kimchi.
Lactobacillus rhamnosus: This is one of the most popular probiotic species found in dietary supplements. Its impact can be observed in reduced anxiety through altering the expression of GABA receptors. It is found in some yoghurts and dairy products, which include fermented and unpasteurised milk and semi‑hard cheese.
Bifidobacterium breve: A beneficial bacterium found in breast milk and in the human gut. However, the amount in the gut decreases with age. It has also been shown to play a role in cognitive abilities, and when it is not concentrated enough, it interferes with the ability to perform tasks. It is also found naturally in some fermented foods.
Lactobacillus reuteri: This probiotic with anti‑inflammatory properties is found in the human gut. However, not all people have it, and some have only very small amounts. One study has shown that the absence of this bacterium causes a social deficit in animals (not yet proven in humans). Adding this strain back into the gut of animals was able to eliminate some of the social behavioural deficits that were similar to symptoms of social anxiety and autism in humans. It is also found in breast milk and some dairy products.
What effect do psychobiotics have?
According to some studies, probiotics (some of which are classified as psychobiotics) can affect the following three systems:
Endocrine - Significantly reduces stress levels (cortisol).
Immune - Significantly increases the production of anti‑inflammatory cytokines.
Nervous - Involved in the production of neurotransmitters, such as serotonin, acetylcholine, GABA, melatonin and histamine.
Neurotransmitters help move information from the gastrointestinal tract directly into our brains. However, further scientific research is still needed to reach definite conclusions.
Gut microbiota and our brain
In terms of evolution, the formation of our entire gut microbiota has played a particularly important role in the proper development of the brain and, subsequently, social interaction. The genes of the human gut microbiota are the most numerous in our body and are capable of producing a myriad of neuroactive compounds. It is now known that these microbes primarily influence cognitive function and basic behavioural patterns such as social interaction and stress correction. In the absence of these microbes, there is a substantial neurochemical change that could explain impairments in cognitive functioning and social interaction. Intake of probiotics and prebiotics may help modulate information processing, which is strongly associated with perceived anxiety and depression and influences the neuroendocrine stress response.
Which psychiatric cases might they benefit?
The first psychiatric case where the use of psychobiotics could have a positive impact is schizophrenia. One of the main problems in the treatment of patients with schizophrenia is usually resistance to the antipsychotic drugs and their subsequent side effects, which include weight gain. The gut microbiota influences both the behaviour of individuals and the metabolism of drugs, which could be related to their ineffectiveness and the negative effects mentioned. Thus, the administration of adequate psychobiotics could possibly influence and reduce adverse effects, but more evidence is needed to support this claim.
Currently, there are a number of studies and research dealing with the use and subsequent observed positive effects in the treatment of anxiety and depressive disorders.
The most recent psychiatric disorder where positive effects have been observed in the treatment of psychobiotics is PAS (autism).
Bottom line
Psychobiotics include probiotics and some prebiotics that are able to produce neuroactive substances that positively affect our central nervous system. There are a number of strains of psychobiotics that can be found in foods such as fermented vegetables and dairy products.
Some psychobiotics have been found to have antidepressant and anxiolytic effects to help in cases of schizophrenia and autism.
