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Posted on: August 3rd, 2021

A healthy microbiota is key to overall health and supporting the microbes in our gut is a major target for many products.  As the authors of one recent study wrote:  “As an imbalance in the intestinal microbiota can lead to the development of several diseases (eg, type 1 diabetes, cancer, among others), the use of prebiotics, probiotics, and postbiotics to alter the gut microbiome has attracted recent interest.”  

The complexity of the microbiota and the many types of approaches to support the microbiome have led to numerous types of supplements, and these go by a variety of names.  Some of our recent news articles have gone over supplements like probiotics and prebiotics.  We will briefly review those, and dive deeper into Postbiotics. 

Probiotics are live bacteria and yeast that, when consumed in adequate amounts, can live in your gut and provide a health benefit.  Prebiotics are ‘healthy food’ for the probiotics and your own gut microbes, and include things like certain types of fibers known to promote the growth of the health-promoting bacteria.  Symbiotics is the term that is used when probiotics and the prebiotics that support them are combined.  

Another concept has now emerged- that of Postbiotics. Postbiotics have been used very broadly and only recently used to describe supplements that provide metabolites produced from prebiotics and probiotics, as well as the non-viable bacteria that have been shown to benefit health.   Let’s dive a little bit deeper specifically into the different definitions and types of postbiotics: What they are and how they may be able to help.

What are Postbiotics?

The term postbiotic was used infrequently until just a few years ago.  In fact, there were fewer than 30 research publications on postbiotics before 2017, whereas since then publications have grown to nearly 100 per year over the last couple of years.  

The first definitions of postbiotics included the byproducts of fiber and prebiotic fermentation, like short-chain fatty acids, which help support colonic epithelial cells as well as modulate clinically relevant metabolic markers like blood cholesterol.  Microbe fragments from lysed probiotics and non-viable microorganisms were also included in these early definitions.  

Basically, anything that resulted from microbiota or probiotics besides the living cells and the prebiotics themselves were pretty much included in these definitions, as long as they were beneficial, with some evidence of showing a physiological is that these are mixtures of substances that have shown a health benefit.   

The field has also been a bit confusing since researchers have also used other terms to describe non-viable beneficial bacteria as well, including paraprobiotics, parapsychobiotics, ghost probiotics, metabiotics, tyndallized probiotics, and bacterial lysates.  

Because so many different terms have been used and this is still an emerging area, it’s not surprising that different definitions exist.  For purposes of this discussion, the term will be used is its broadest meaning.  However, just this year, an influential scientific consensus group has proposed limiting the definition.  Therefore, in the future, the term may be used in a more limited manner. 

Scientists Provide a More Limited Definition of Postbiotics

The definition of postbiotics is in flux and a comprehensive definition of what a postbiotic is hasn’t been available.  Just this year, an international panel of scientific experts under the auspices of the International Scientific Association for Probiotics and Prebiotics (ISAPP) updated their definition and scope for what a postbiotic is.  Based on this new consensus agreement, a postbiotic is defined as “a preparation of inanimate microorganisms and/or their components that confers a health benefit on the host.”  Another way to say that is: Postbiotics describe non-viable, or non-living bacteria that confer a health benefit.  One of the benefits of postbiotics is that they aren’t living, and some people have been concerned about new bacteria are being introduced to the body.

Given that this group includes experts in the prebiotic and probiotic area, it is likely this more limited definition will become the standard.  Time will tell.  However, up to now, postbiotics have been the name generally used for any beneficial substances released by microorganisms (including probiotics), as well as the components or inanimate (non-viable) microbes themselves.  

Although the definition is in question, what isn’t in question is that not only probiotics and prebiotics are beneficial, but the products of probiotic fermentation, as well as probiotic byproducts and non-viable cells, can also be beneficial.  

Examples of Postbiotics

The list below provides examples of groups of beneficial substances that are produced by the metabolic activity of microorganisms in the gut as well as byproducts from beneficial microbes and probiotics, which using the broadest definition are considered postbiotics.  Some of these directly affect the bacteria and other microbes in the gut. For example, a postbiotic may decrease the growth of a non-beneficial or harmful microbe in the gut.  Other postbiotic clinical effects that are currently being researched:

  • Preventing respiratory tract infections
  • Symptoms of Irritable Bowel Syndrome
  • Mitigating Stress

Many postbiotics are not currently widely available, as many studies are still being conducted on their value. Some postbiotic supplements are available at specialty nutrition retailers, however, and usually feature common ingredients.

Short-chain fatty acids (SCFAs)

Short-chain fatty acids (SCFAs) are produced by intestinal microbiota fermentation of plant-based polysaccharides, like fibers and prebiotics. There are specific types of short-chain fatty acids that are produced, including butyric (butanoic), acetic, and propionic acids.  

Different fibers and prebiotics, along with the different microbiota result in different ratios of these SCFAs which can lead to different effects.  Of these SCFAs, however, butyric acid is considered extremely important. 

Butyric acid is also called butyrate and is a key energy source for intestinal absorptive cells (enterocytes). Butyrate has immunosuppressive effects and can help with food tolerance, aiding digestion.

Antioxidant Components?

Microorganisms are capable of producing antioxidant components, which are useful in protecting against potential damage from nucleic acids, proteins, lipids, and carbohydrates. Some types of antioxidant components are enzymes and include NADH-oxidase, peroxide dismutase, and glutathione peroxidase.

Early research into postbiotic antioxidant enzymes has shown promise in relieving symptoms in Crohn’s disease and IBD. Studies are currently being conducted on how postbiotics affect the development and prevention of colon cancer.

Cell-Free Supernatants

Cell-free supernatants are mixes of active metabolites released by gut bacteria and yeast. Supernatants have been observed to have different health effects. Some have been shown to be anti-inflammatory, while others aid in antioxidant production.

Studies have shown effects from supernatants may involve decreased production of the inflammatory tumor necrosis factor cytokine and cytokine interleukin 10.

These effects are mediated by decreased secretion of pro-inflammatory tumor necrosis factor α (TNF-α) cytokine and increased secretion of the anti-inflammatory cytokine interleukin 10 (IL-10).

Cell Wall Fragments

The bacterial cell wall in the gut has expressed immunogenic potential when specific components are looked at individually. Positive byproducts of the cell wall can be directly introduced into the gut, with potentially beneficial effects.

Current research is looking into many potential health benefits of bacterial cell walls, with areas showing some promise including:

  • Skin infections
  • Anti-infectious peptides
  • Anti-inflammation
  • Antineoplastic properties
  • Immunomodulatory effects.

Exopolysaccharides

Microorganisms in the gut produce biopolymers as they grow. Certain mixtures of these biopolymers are called exopolysaccharides. Exopolysaccharides are used as stabilizers, emulsifiers, and water-binding agents. 

Exopolysaccharides are still being studied and their exact biologic functions are not currently understood. Ongoing research is observing the relationship between exopolysaccharides and cholesterol. 

What Postbiotics Should I Look for?

As amazing as many of the potential health benefits from postbiotics sound, research is still being conducted. The study of postbiotics is only just beginning to pick up.

Keeping track of research, looking at the ingredients of new postbiotics, and talking to your doctor are great ways to learn more about the progression of postbiotics and postbiotic research.

The Potential Impacts of Postbiotic Research

Modern strategies for changing the human gut microbiome usually include dietary modifications and/or biotherapeutics. Postbiotics have shown potential to be a game-changer in the field of gut microbiome research.

It is important to note that not all bacteria in the gut and their associated byproducts have health benefits. This is important to note due to the volume of bacteria in the gut. 

“For instance, in 2019 Patrice D. Cani and colleagues showed that metabolic outcomes in individuals who are overweight and obese when treated with pasteurized Akkermansia muciniphila were more consistent compared to individuals who received live A. muciniphila.”

The new definition of postbiotics can include metabolites if they are accompanied by non-living microbial biomasses, like what is found in fermented foods. Purified microbe-derived substances (butyrate etc), however, are not considered postbiotics.

Are Postbiotics Safe to Use as Dietary Supplements?

The new definition of postbiotics notes that they may be taken as supplements, prescription drugs, and food in general. But the consensus definition of postbiotic also came with many concerns from researchers. Regulatory challenges and specific criteria for health and safety came into question during discussions.

Postbiotics must be initially prepared from a living microorganism but treated in such a way to not be able to replicate, which requires a specific process when conducted in a lab. Lab temperatures, cleanliness, and drying are all important in safety and quality considerations, and standards should be put into place

“On the whole, postbiotics include inanimate microbes with or without metabolites that have been shown to have health benefits and are likely to be safer and more stable than live counterparts. As in the case of probiotics and prebiotics, clinical trials in different populations are needed before their systematic use is recommended.”

Research at Biofortis

As amazing as the many potential benefits of postbiotics sound, research confirming these benefits are still in their infancy. Scientists and researchers are still learning the process of how to consistently develop healthy postbiotics and the specific requirements and types of postbiotics for each outcome or condition. 

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