Most people are familiar with prebiotics and probiotics. Probiotics are live microorganisms that inhabit the gut microbiome and are beneficial for health. Prebiotics are a non-digestible fibre that stimulates the growth and activity of beneficial bacteria. Synbiotics contain both probiotics and prebiotics. Probiotics, prebiotics and synbiotics are generally considered beneficial for gut health, with strong evidence base for many of these supplements.

What are postbiotics?

Postbiotic supplements contain bacterial products and cell fragments or even whole, inactivated or heat-killed bacterial cells that have are believed to have a therapeutic effect. The International Scientific Association for Probiotics and Prebiotics (ISAPP) defines a postbiotic supplement as ‘a preparation of inanimate microorganisms and/or their components that confers a health benefit on the host.’  

Postbiotics can include:

• short chain fatty acids (SCFA), like butyrate

• inactivated or heat-killed bacterial cells

• bacterial cell wall fragments

• peptides and proteins

• enzymes

• carbohydrate polymers

• other fermentation derived compounds

One of the advantages of postbiotics is that they contain no live organisms. This may be helpful because they do not need to be refrigerated (like some probiotics do), and they could be safely consumed by immunocompromised clients who may not be able to take probiotics.

What does the research say about their benefits?

Recent studies suggest postbiotics may support gut health through three main mechanisms.

1. Immune modulation – microbial cell components interact with immune receptors, helping regulate inflammatory responses by reducing the release of pro-inflammatory chemical messengers known as cytokines.

2. Gut barrier support – some postbiotics may improve gut lining integrity, through the action of the short chain fatty acid butyrate which can help tighten cell walls and reduce intestinal permeability (aka leaky gut).

3. Promoting antimicrobial activity – the different cell components have been shown to protect against gut pathogens.

Some examples of postbiotics

A good example of a postbiotic is butyrate, an important short chain fatty acid that plays a key role in maintaining the integrity of the gut lining, amongst many other benefits. We have been using butyrate in clinical practice for several years now, for very specific purposes, and the results have been consistently promising, with an excellent safety profile. More often though, we use prebiotics to feed up the butyrate-producing bacteria in the gut as this delivers higher ‘doses’ of butyrate right where it’s needed.

                                                                            

While butyrate is a single bacterial metabolite, a very different supplement has been developed in the United States. It’s a postbiotic that is derived from carefully screened human donors, rigorously tested for disease and selected for their healthy, biodiverse microbiome. However, there are currently no peer-reviewed studies on this product, therefore we would not recommend this product in our treatment plans.

Other products on the market contain a product derived from anaerobically fermenting Saccharomyces cerevisiae (baker’s yeast). This product has undergone clinical research, and the postbiotics themselves have also been clinically tested. It is used in a few products that I found while researching and while I won’t prescribe them yet, I do plan on trying them out on myself.

Postbiotics are also naturally found in fermented foods, including those that have been pasteurised or cooked. It’s long been thought that these postbiotics can have beneficial effects even without live bacteria present. For example, sourdough bread includes beneficial acids produced during the proving process and of course the bacteria and yeasts introduced through the sourdough culture that don’t survive the oven.

Looking to the future

If you are experiencing gut symptoms and have been struggling to get answers, please get in touch. My focus is on discovering the root cause of gut issues through testing and evidence-based treatment protocols.

Vicky Ellenport BHSc NUT is a registered Clinical Nutritionist and Microbiome Analyst. 

REFERENCES

Guo et al (2025). Effects of Lactobacillus paracei JY062 Postbiotic on Intestinal Barrier, Immunity, and Gut Microbiota. Nutrients, 17(7), 1272. https://doi.org/10.3390/nu17071272

Possemiers et al. (2013). A dried yeast fermentate selectively modulates both the luminal and mucosal gut microbiota and protects against inflammation, as studied in an integrated in vitro approach. J Agric Food Chem doi: https://doi.org/10.1021/jf402137r

Smolinska et al (2025).  A Review of the Influence of Prebiotics, Probiotics, Synbiotics, and Postbiotics on the Human Gut Microbiome and Intestinal Integrity. J. Clin. Med. 14, 3673. https://doi.org/10.3390/jcm14113673

Yang et al (2023). Tributyrin alleviates gut microbiota dysbiosis to repair intestinal damage in antibiotic-treated mice. PLoS One. https://doi.org/10.1371/journal.pone.0289364

Żółkiewicz et al (2020) Postbiotics-A Step Beyond Pre- and Probiotics. Nutrients. https://doi.org/10.3390/nu12082189