What are postbiotics and how do they reduce infection risk?
Postbiotics are non-living bacterial components or their metabolic byproducts—like heat-killed bacteria, culture supernatants, or fermented metabolites—that provide health benefits without the risks of live probiotics. They work by directly inhibiting pathogens, boosting the immune system, and reducing inflammation. For example, in a mouse study, postbiotics from Lactiplantibacillus plantarum directly suppressed Salmonella growth and reduced the bacteria's ability to cause disease by lowering the expression of virulence genes (like SopE and InvA) and biofilm formation [5]. In fish, postbiotics from Bacillus velezensis activated both innate antiviral genes (dhx58, trim25) and adaptive immune genes (igm, igt), increasing IgM+ B cells and enhancing antiviral defense [4].
What does human evidence show about postbiotics and infection?
The strongest human evidence comes from a randomized controlled trial of 120 stroke patients in the ICU, where postbiotic supplementation for 7 days significantly reduced the incidence of pneumonia compared to placebo [1]. The postbiotic group showed notable decreases in inflammatory markers: serum IL-1β dropped by 1.79 units (95% CI: -2.9 to -0.64), high-sensitivity C-reactive protein (Hs-CRP) fell by 0.67 mg/dL, and oxidative stress marker MDA decreased by 30.5 units [1]. These changes directly correlate with lower infection risk, though the study did not find significant improvements in other clinical outcomes like stroke severity scores [1].
Do animal and veterinary studies support the infection-fighting potential?
Yes, multiple animal and veterinary studies converge on the same conclusion: postbiotics reduce infection risk through multiple mechanisms. In mice, postbiotics from Lactiplantibacillus plantarum not only suppressed Salmonella infection but also reduced intestinal damage, increased tight junction proteins (Occludin and Claudin-1), and regulated inflammation by increasing anti-inflammatory cytokines IL-4 and IL-10 while decreasing TNF-α [5]. In dogs, oral postbiotic supplementation reduced the prevalence of Staphylococcus pseudintermedius (a common skin pathogen) in inguinal tissue and increased beneficial skin bacteria like Dubosiella newyorkensis and Lactobacillus acidophilus, suggesting reduced risk of skin infections [2]. In horses, postbiotics from Saccharomyces cerevisiae helped stabilize hindgut pH during high-starch fermentation, reducing lactate accumulation and acidosis risk—a condition that predisposes to gut infections [3]. These studies, while not human clinical trials, provide mechanistic evidence that postbiotics can meaningfully alter infection risk across species.
About These Sources
This answer is built on 5 peer-reviewed studies — published from 2023 to 2026, 4 from 2024 or later, 3 in Q1 journals — selected as the most relevant from 5 studies that passed quality screening, drawn from 46 papers retrieved from a database of over 500 million.
Sources used in this answer
Clinical trial of the effects of postbiotic supplementation on inflammation, oxidative stress, and clinical outcomes in patients with CVA
In a randomized controlled trial of 120 stroke patients, 7 days of postbiotic supplementation significantly reduced pneumonia incidence and improved inflammatory markers (IL-1β, Hs-CRP, MDA) compared to placebo, though other clinical outcomes like stroke severity scores did not differ.
The effect of daily oral probiotic and postbiotic supplementation on the canine skin microbiota: Insights from culture‐dependent and long‐read <scp>16S rRNA</scp> gene sequencing methods
In a prospective cohort study of 12 dogs, 90 days of oral postbiotic supplementation reduced Staphylococcus pseudintermedius prevalence in inguinal skin and increased beneficial bacteria (Dubosiella newyorkensis, Lactobacillus acidophilus), suggesting reduced skin infection risk.
An in vitro investigation into the effects of postbiotic supplementation on stabilising equine hindgut pH
In an in vitro equine hindgut model, Saccharomyces cerevisiae-derived postbiotics at two doses significantly reduced pH decline and lactate accumulation during high-starch fermentation, indicating reduced acidosis risk, though acidosis was not fully prevented.
Bacillus velezensis-fermented postbiotics as feed additives for viral infection control in largemouth bass (Micropterus salmoides).
In largemouth bass, Bacillus velezensis-fermented postbiotics (50 mL/kg) promoted growth, upregulated innate antiviral genes (dhx58, trim25, mx1, ifnγ) and adaptive immune genes (igm, igt, cd8α, cd4), increased IgM+ B cells, and enhanced antiviral defense against viral infection.
Lactiplantibacillus plantarum Postbiotics Suppress Salmonella Infection via Modulating Bacterial Pathogenicity, Autophagy and Inflammasome in Mice
In mice, Lactiplantibacillus plantarum-derived postbiotics suppressed Salmonella infection by reducing virulence genes, biofilm formation, and activating autophagy via AMPK signaling, while decreasing NLRP3 inflammasome activation and intestinal damage.