Yeast Mannan

Yeast mannan (mannan-oligosaccharides/MOS) is a polysaccharide from yeast cell walls. Indigestible by humans but fermented by gut bacteria, acting as a prebiotic. Used primarily in animal nutrition to support gut health and immunity. NO GRADED OUTCOMES in humans - research is mostly in animals. May have immune-modulating effects. Part of yeast beta-glucan/MOS products. Generally safe.

Quick Answer

What it is

Yeast mannan (mannan-oligosaccharides/MOS) is a polysaccharide from yeast cell walls. Indigestible by humans but fermented by gut bacteria, acting as a prebiotic.

Key findings

Grade C: Immune Function
Grade D: Gut Microbiome Composition
Grade D: Gut Barrier Integrity

Safety

No specific caution or interaction language was detected in the current summary/outcome notes.

ℹ️ Quick Facts: Yeast Mannan

Quick Facts: Yeast Mannan

Best Evidence:Grade C
Conditions Studied:2
Research Outcomes:4
Key Effect:Autoimmune Health

Outcomes by grade:

2 conditions · 4 outcomes

Detailed Outcomes

Immune Function

Multiple animal studies across fish, mice, and poultry consistently demonstrate immune-modulatory effects of MOS, including enhanced innate immune parameters and improved immune responses to pathogen challenge. A mouse study (PMID:29723205) confirmed immune-modulatory properties of dietary yeast-derived MOS, though no human clinical trials exist.

small↑Improves

Gut Microbiome Composition

An in vitro canine gastrointestinal model found dried yeast cell walls high in beta-glucan and MOS positively affected microbial composition and fermentation activity. Additional poultry studies showed effects on jejunal gene expression and gut morphology, supporting prebiotic activity across species.

small↑Improves

Gut Barrier Integrity

In European sea bass, dietary MOS significantly reduced gut bacterial translocation, suggesting improved intestinal barrier function. Broiler chicken studies also showed improved gut morphology with MOS supplementation, though no human data exist.

small↑Improves

Infection Resistance

In European sea bass, MOS feeding improved survival following pathogen challenge. A broiler chicken study demonstrated improved responses to Salmonella typhimurium challenge with dietary yeast cell wall components including MOS. Evidence is limited to animal models.

small↑Improves

Evidence by Condition

Best grade per condition (each condition may have multiple outcomes)

CAutoimmune Health

1 outcome · 4 studies

↑Immune FunctionImproves

DAcute Respiratory Infection (ARI)

1 outcome · 2 studies

↑Infection ResistanceImproves

Research Citations (7)

Comparative effects of Saccharomyces cerevisiae, mannan-oligosaccharides, and their synbiotic on growth performance, gut morphology, immune responses, and economic efficiency in broiler chickens.

Poultry Science (2026)

PMID: 41610607

Response of broiler chickens to dietary different yeast cell wall components challenged with Salmonella typhimurium.

Veterinary Research Communications (2025)

PMID: 40996575

Dried yeast cell walls high in beta-glucan and mannan-oligosaccharides positively affect microbial composition and activity in the canine gastrointestinal tract in vitro.

Journal of Animal Science (2020)

PMID: 32497185

Dietary yeast-derived mannan oligosaccharides have immune-modulatory properties but do not improve high fat diet-induced obesity and glucose intolerance.

PLoS ONE (2018)

PMID: 29723205

Effects of yeast cell wall-derived mannan-oligosaccharides on jejunal gene expression in young broiler chickens.

Poultry Science (2012)

PMID: 22700513

Reduced gut bacterial translocation in European sea bass (Dicentrarchus labrax) fed mannan oligosaccharides (MOS).

Fish & Shellfish Immunology (2011)

PMID: 21195771

Immune stimulation and improved infection resistance in European sea bass (Dicentrarchus labrax) fed mannan oligosaccharides.

Fish & Shellfish Immunology (2007)

PMID: 17766145

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