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.
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.
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.
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