Postbiotics

Definition

Postbiotics are the metabolic byproducts produced when probiotic bacteria ferment food in the gut — or in some cases, the heat-treated/inactivated bacteria themselves. The category includes:

• Short-chain fatty acids (SCFAs): Butyrate, propionate, acetate — produced when gut bacteria ferment dietary fibre. Butyrate is the primary energy source for colonocytes (colon cells) and has strong mechanistic evidence for maintaining gut barrier integrity (Hamer et al, Aliment Pharmacol Ther 2008, PMID 17900326).
• Enzymes: Produced by bacteria during fermentation (lipases, proteases).
• Bacteriocins: Antimicrobial peptides produced by probiotic bacteria that may suppress pathogenic species.
• Cell wall fragments: Peptidoglycan and lipopolysaccharide components that may modulate immune responses.

Is the Evidence Base Robust?

Postbiotics are the newest category in gut supplement science. The mechanistic evidence is strong — butyrate’s role in colonocyte function and gut barrier integrity is well-established. What is less clear is whether consuming postbiotic supplements produces the same effects as producing postbiotics endogenously through a fibre-rich diet.

A 2021 consensus definition paper (Salminen et al, Nat Rev Gastroenterol Hepatol 2021, PMID 34302062) established a formal definition: “a preparation of inanimate microorganisms and/or their components that confers a health benefit on the host.” This formalised the category but the clinical trial evidence for consumer supplement products remains limited compared with probiotics.

Ritual Synbiotic+ and Tributyrin

Ritual Synbiotic+ includes tributyrin — a form of butyrate precursor — as its postbiotic component. Tributyrin is hydrolysed to butyrate in the small intestine, where it may support gut barrier function. The human trial evidence for tributyrin supplementation in healthy adults is limited to small studies; the mechanistic rationale is sound but the consumer-relevant outcomes are not yet as robustly demonstrated as for LGG or B. infantis 35624.

Bottom Line

Postbiotics are a scientifically legitimate category with strong mechanistic underpinnings. The clinical trial evidence for consumer postbiotic supplements (vs. producing postbiotics naturally through diet) is emerging. Look for specific postbiotic compounds (butyrate, specific bacteriocins) with at least one human RCT for the outcome you care about before purchasing.