Flash Cards

Prebiotics vs. Postbiotics: Definitions, Mechanisms and Examples

Prebiotics are naturally occurring compounds from dietary plants that undergo degradation by gut bacteria.  Some degradation products are biologically active metabolites (postbiotics), which can impart systemic health benefits to the host.  The infographic below summarizes five mechanisms by which these compounds support gut health. 

Figure 1. Functions of prebiotics in the GI tract include expansion of beneficial microbial species, serotonergic effects, barrier integrity, protective mucin production and synthesis of biologically active, bioavailable metabolites, such as SCFA (from fiber, FOS, GOS and XOS), tryptamine (from tryptophan) and urolithins (from ellagitannins).

Examples of prebiotics include dietary fiber (long beta-linked polysaccharides), fructo-oligosaccharides (FOS), galacto-oligosaccharides (GOS) and xylo-oligosaccharides (XOS).  These compounds support the growth of beneficial bacteria. They also support the synthesis of small molecules that are more bioavailable and enter the circulation, contributing to systemic health benefits of undigestible plant fibers.

Postbiotics are bioactive metabolites of bacterial metabolism. Examples include short-chain fatty acids (SCFAs), products of fermentation of poly- and oligosaccharides that serve as energy substrates for intestinal epithelial cells.  One of the most extensively studied SCFA is butyrate, which supports immunity, IgA production, barrier function, cellular energy and tissue repair.  Other examples of postbiotics include phenolic acids and urolithins from dietary polyphenols, and dihydroberberine, a more absorbable derivative of the alkaloid berberine generated by microbial nitroreductases.

Figure 2. Metabolism of SCFAs from dietary fiber. SCFAs are a major energy source for intestinal epithelial cells. They are also absorbed into the portal blood, with a small fraction entering the systemic circulation and accessing distant organs. Figure courtesy of BioRender.com, Metabolism of SCFAs.

Some postbiotics resemble neurotransmitters and hormones.  For example, tryptamine is a microbial metabolite of tryptophan that activates intestinal 5-HT4 receptors that control motility and secretions. This serotonergic prokinetic agent holds promise as a therapeutic modality for functional GI disorders.

A vast assortment of bioactive postbiotics arise from the microbiota.  Known as the gut metabolome, this chemical library is influenced by diet, lifestyle, genetics, medications and health status. It also holds potential lead compounds for drug and dietary ingredient development.

Further Reading

Dey P. Gut microbiota in phytopharmacology: A comprehensive overview of concepts, reciprocal interactions, biotransformations and mode of actions. Pharmacol Res. 2019 Sep;147:104367.

Żółkiewicz J, Marzec A, Ruszczyński M, Feleszko W. Postbiotics-A Step Beyond Pre- and Probiotics. Nutrients. 2020 Jul 23;12(8):2189.

Bhattarai Y, Williams BB, Battaglioli EJ, et al. Gut Microbiota-Produced Tryptamine Activates an Epithelial G-Protein-Coupled Receptor to Increase Colonic Secretion. Cell Host Microbe. 2018 Jun 13;23(6):775-785.e5.  

Bridgeman SC, Northrop W, Melton PE, et al. Butyrate generated by gut microbiota and its therapeutic role in metabolic syndrome. Pharmacol Res. 2020 Oct;160:105174.

Cardona F, Andrés-Lacueva C, Tulipani S, et al. Benefits of polyphenols on gut microbiota and implications in human health. J Nutr Biochem. 2013 Aug;24(8):1415-22.

Sorrenti V, Ali S, Mancin L, Davinelli S, Paoli A, Scapagnini G. Cocoa Polyphenols and Gut Microbiota Interplay: Bioavailability, Prebiotic Effect, and Impact on Human Health. Nutrients. 2020 Jun 27;12(7):1908.

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