Psychobiotics is a term used in preliminary research to refer to live bacteria that, when ingested in appropriate amounts, might confer a

mental health Mental health encompasses emotional, psychological, and social well-being, influencing cognition, perception, and behavior. It likewise determines how an individual handles stress, interpersonal relationships, and decision-making. Mental health ...

benefit by affecting

microbiota Microbiota are the range of microorganisms that may be commensal, symbiotic, or pathogenic found in and on all multicellular organisms, including plants. Microbiota include bacteria, archaea, protists, fungi, and viruses, and have been found t ...

of the host organism. Whether bacteria might play a role in the gut-brain axis is under research. A 2020 literature review suggests that the consumption of psychobiotics could be considered as a viable option to restore mental health although lacking

randomized controlled trials A randomized controlled trial (or randomized control trial; RCT) is a form of scientific experiment used to control factors not under direct experimental control. Examples of RCTs are clinical trials that compare the effects of drugs, surgical te ...

on clear mental health outcomes in humans.

Types

In experimental probiotic psychobiotics, the bacteria most commonly used are

gram-positive bacteria In bacteriology, gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their type of cell wall. Gram-positive bact ...

, such as ''

Bifidobacterium ''Bifidobacterium'' is a genus of gram-positive, nonmotile, often branched anaerobic bacteria. They are ubiquitous inhabitants of the gastrointestinal tract though strains have been isolated from the vagina and mouth ('' B. dentium'') of mammal ...

'' and ''

Lactobacillus ''Lactobacillus'' is a genus of Gram-positive, aerotolerant anaerobes or microaerophilic, rod-shaped, non-spore-forming bacteria. Until 2020, the genus ''Lactobacillus'' comprised over 260 phylogenetically, ecologically, and metabolically diver ...

'' families, as these do not contain

lipopolysaccharide Lipopolysaccharides (LPS) are large molecules consisting of a lipid and a polysaccharide that are bacterial toxins. They are composed of an O-antigen, an outer core, and an inner core all joined by a covalent bond, and are found in the outer m ...

chains, reducing the likelihood of an

immunological response An immune response is a reaction which occurs within an organism for the purpose of defending against foreign invaders. These invaders include a wide variety of different microorganisms including viruses, bacteria, parasites, and fungi which could ...

Prebiotics Prebiotics are compounds in food that induce the growth or activity of beneficial microorganisms such as bacteria and fungi. The most common example is in the gastrointestinal tract, where prebiotics can alter the composition of organisms in the ...

are substances, such as

fructans A fructan is a polymer of fructose molecules. Fructans with a short chain length are known as fructooligosaccharides. Fructans can be found in over 12% of the angiosperms including both monocots and dicots such as agave, artichokes, asparagus, leek ...

and

oligosaccharides An oligosaccharide (/ˌɑlɪgoʊˈsækəˌɹaɪd/; from the Greek ὀλίγος ''olígos'', "a few", and σάκχαρ ''sácchar'', "sugar") is a saccharide polymer containing a small number (typically two to ten) of monosaccharides (simple sugar ...

, that induce the growth or activity of beneficial

microorganism A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...

s, such as bacteria on being

fermented Fermentation is a metabolic process that produces chemical changes in organic substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in the absence of oxygen. In food ...

in the gut. Multiple bacterial species contained in a single probiotic broth is known as a polybiotic.

Research

A 2021 review showed that treating anxiety in young people with psychobiotics had no significant effect. There is a need for more diverse human studies, mainly because those that exist have contradictory outcomes.

Species

Several species of bacteria have been used in probiotic psychobiotic research: *

Lactobacillus helveticus ''Lactobacillus helveticus'' is a lactic-acid producing, rod-shaped bacterium of the genus ''Lactobacillus''. It is most commonly used in the production of American Swiss cheese and Emmental cheese, but is also sometimes used in making other st ...

Bifidobacterium longum ''Bifidobacterium longum'' is a Gram-positive, catalase-negative, rod-shaped bacterium present in the human gastrointestinal tract and one of the 32 species that belong to the genus ''Bifidobacterium''. It is a microaerotolerant anaerobe and co ...

Lactobacillus casei ''Lacticaseibacillus casei ''is an organism that belongs to the largest genus in the family ''Lactobacillaceae'', a lactic acid bacteria (LAB), that was previously classified as ''Lactobacillus casei-01''. This bacteria has been identified as facu ...

Lactobacillus plantarum ''Lactiplantibacillus plantarum'' (formerly ''Lactobacillus arabinosus'' and ''Lactobacillus plantarum'') is a widespread member of the genus ''Lactiplantibacillus'' and commonly found in many fermented food products as well as anaerobic plant ma ...

Lactobacillus acidophilus ''Lactobacillus acidophilus'' (New Latin 'acid-loving milk-bacillus') is a rod-shaped, Gram-positive, homofermentative, anaerobic microbe first isolated from infant feces in the year 1900. The species is most commonly found in humans, specifically ...

Lactobacillus delbrueckii subsp. bulgaricus ''Lactobacillus delbrueckii'' subsp. ''bulgaricus'' (until 2014 known as ''Lactobacillus bulgaricus'') is one of over 200 published species in the ''Lactobacillus'' genome complex (LGC) and is the main bacterium used for the production of yogurt. ...

Bifidobacterium breve ''Bifidobacterium breve'' is a bacterial species of the genus ''Bifidobacterium'' which has probiotic properties. ''Bifidobacteria'' are a type of bacteria that live symbiotically in the intestines of humans. They have been used to treat a number ...

Bifidobacterium infantis ''Bifidobacterium longum'' is a Gram-positive, catalase-negative, rod-shaped bacterium present in the human gastrointestinal tract and one of the 32 species that belong to the genus ''Bifidobacterium''. It is a microaerotolerant anaerobe and con ...

Streptococcus salivarius ''Streptococcus salivarius'' is a species of spherical, gram-positive, facultative anaerobic lactic acid bacteria that is both catalase and oxidase negative. ''S. salivarius'' colonizes (usually in chains) the oral cavity and upper respiratory ...

Lactobacillus rhamnosus ''Lacticaseibacillus rhamnosus'' (previously ''Lactobacillus rhamnosus'') is a bacterium that originally was considered to be a subspecies of '' L. casei'', but genetic research found it to be a separate species in the ''L. casei'' clade, which ...

*'' Lactobacillus gasseri''

References

{{Dietary supplement Bacteriology Digestive system Gut flora