From gut flora to immune mechanisms: more and more research shows that our immune system works closely with the bacteria in our gut. But while probiotics and prebiotics have long been in the spotlight, a new key player is emerging: postbiotics.
What does science say about postbiotics and their relationship to our immunity? What exactly are postbiotics? And what happens in your body when they become active? In this blog, we'll take you through the most striking findings from recent research.
First, what are postbiotics?
Postbiotics are the bioactive substances produced when bacteria in your gut break down fibers or other nutrients. They include, among others:
- Short-chain fatty acids (such as butyric acid, acetic acid, propionic acid)
- Bacterial cell components (such as lipopolysaccharides, peptidoglycans)
- Enzymes, peptides, vitamins, and other signaling molecules
Where probiotics are living bacteria, postbiotics are the functional compounds these bacteria produce. And it is precisely these compounds that seem to play a direct role in the communication between the gut and the immune system.
1. Butyric acid and regulation of immune responses
One of the best-researched postbiotics is butyric acid (butyrate): a short-chain fatty acid produced during the fermentation of dietary fibers. Multiple studies show that butyric acid influences the regulation of the immune system:
"Butyrate has been shown to modulate the differentiation and activity of regulatory T cells (Tregs), which play a crucial role in maintaining immune tolerance."
— Furusawa et al., Nature, 2013
Regulatory T cells are essential for keeping overactive immune responses in check. So, in simple terms: if your gut bacteria get enough fiber, they can produce butyric acid, and that is linked to a better-tuned immune response. Not overactive, but not too weak either.
2. Postbiotics as ‘signaling molecules’ for immune cells
Postbiotics communicate with the immune system via specific receptors. According to a review study in Frontiers in Immunology:
"Postbiotics interact with pattern recognition receptors (PRRs), such as toll-like receptors (TLRs), which are important in immune system signaling pathways."
— Aguilar-Toalá et al., 2021
These receptors act as messengers between your gut bacteria and your immune system. This makes them interesting for research into how your gut and immune system stay coordinated.
3. Role of postbiotics in training the immune system
In the first years of life, the immune system is trained, partly through contact with bacteria and their byproducts. A study published in Cell Host & Microbe suggests that postbiotics may play a role in this:
"Microbial metabolites, such as short-chain fatty acids (SCFAs), play a role in educating the host immune system by promoting tolerance and reducing hypersensitivity."
— Belkaid & Hand, 2014
This gives rise to research into how postbiotics can play a role in immune maturation, especially in young children and in the prevention of allergies.
4. Butyric acid and the intestinal barrier
The immune system begins with a well-functioning intestinal wall. Studies show that butyric acid affects the expression of ‘tight junctions’ (connections between intestinal cells):
"Butyric acid improves intestinal barrier function by increasing the expression of tight junction proteins."
— Peng et al., The Journal of Nutrition (2009)
A well-functioning intestinal wall means that unwanted substances are less likely to ‘leak through’. And that is beneficial for your overall resistance and balance.
Finally: what can we conclude from this?
Science is still actively unraveling exactly how postbiotics work. But one thing is becoming increasingly clear: these small substances are powerful links between nutrition, gut, and defense.
They provide insight into why fiber-rich foods, fermented products, and gut diversity are so important. And why your gut rarely stands ‘alone’ when it comes to health.
Sources:
Aguilar-Toalá et al., Postbiotics: An evolving term within the functional foods field, Frontiers in Immunology (2021)
DOI: 10.3389/fimmu.2021.622943
Belkaid & Hand, Role of the microbiota in immunity and inflammation, Cell Host & Microbe (2014)
DOI: 10.1016/j.chom.2014.05.008
Furusawa et al., Commensal microbe-derived butyrate induces the differentiation of colonic regulatory T cells, Nature (2013)
DOI: 10.1038/nature12721
Peng et al., Butyrate enhances intestinal barrier function, The Journal of Nutrition (2009)
DOI: 10.3945/jn.108.100586
