What we know
✓ Some laboratory protocols report high digestibility.
✓ A rat and laboratory study reported lower measures than several comparators.
✓ Cell-wall disruption and separation methods may matter.
What we don’t know yet
? Which laboratory measure best predicts human availability.
? How commercial products compare under standardized human methods.
Why the numbers disagree
Cao and colleagues found lower true protein and ileal amino-acid digestibility for their yeast isolate. Qiao and colleagues reported 97.66% digestibility in one in-vitro protocol, close to whey isolate. Caron and colleagues found comparable in-vitro digestion to whey and casein.
These findings should not be averaged into a marketing number. They used different preparations and experimental systems. Cell walls, mechanical disruption, enzyme treatment and purification can all affect protein accessibility.
Evaluation of the nutritional quality of yeast protein in comparison to animal and plant proteins using growing rats and INFOGEST model
Yeast protein had a strong indispensable-amino-acid profile, but lower measured true protein and ileal amino-acid digestibility than comparison proteins in this experiment.
Cao X, Liu H, Yang M, Mao K, Wang X, Chen Z, Ran M, Hao L · 2025 · Food Chemistry
DOI 10.1016/j.foodchem.2024.141178 ↗Research on the release and absorption regularities of free amino acids and peptides in vitro digestion of yeast protein
One protocol reported 97.66% digestibility for the tested yeast protein, close to whey isolate, with model-specific amino-acid and peptide release patterns.
Qiao K et al. · 2025 · Food Chemistry
DOI 10.1016/j.foodchem.2025.144176 ↗In vitro human gastrointestinal digestibility and colonic fermentation of edible yeast-based protein
The tested yeast protein showed comparable in-vitro digestibility and a distinct fermentation and metabolomic profile.
Caron J et al. · 2025 · Food Research International 208:116098
DOI 10.1016/j.foodres.2025.116098 ↗View references (3)
- Cao X, Liu H, Yang M, Mao K, Wang X, Chen Z, Ran M, Hao L. (2025). Evaluation of the nutritional quality of yeast protein in comparison to animal and plant proteins using growing rats and INFOGEST model. Food Chemistry. https://doi.org/10.1016/j.foodchem.2024.141178
- Qiao K et al.. (2025). Research on the release and absorption regularities of free amino acids and peptides in vitro digestion of yeast protein. Food Chemistry. https://doi.org/10.1016/j.foodchem.2025.144176
- Caron J et al.. (2025). In vitro human gastrointestinal digestibility and colonic fermentation of edible yeast-based protein. Food Research International 208:116098. https://doi.org/10.1016/j.foodres.2025.116098