The Study
In vitro protein digestibility of different soy-based products: effects of microstructure, physico-chemical properties and protein aggregation.
This study looked at four types of soy food in a test tube to see how easily enzymes could break down their proteins. It found that some foods digested more easily than others, and that this had to do with how their proteins were folded. But it didn't test this in people or prove that one food is better than another for your body.
Analysis score
Maximum 44 for a cross-sectional study.
Where the score came from
Scientists tested how easily your body can break down four soy foods: soy milk, soy powder, tofu, and yuba (soy skin). They found that tofu breaks down the easiest, and soy milk the hardest.
Where does this study sit?
Reviews of RCTs (Meta-analyses)
Max 100Randomized Trials
Max 90Reviews of Cohort Studies
Max 85Cohort Studies
Max 72Reviews of Case-Control Studies
Max 63Case-Control Studies
Max 58Cross-Sectional & Case Series
Max 50Expert Opinion
Max 57 / 100
Quality score
Snapshots of a population at a single point in time, or descriptions of small groups. Can identify correlations and prevalence, but cannot determine cause and effect.
Key takeaways
Summary
Based on the study abstract and findings.
- 1This means tofu gives your body more usable protein than soy milk, even though they come from the same beans — because how the soy is processed changes how well your stomach can digest it.
- 2Tofu released 41.0 mmol of amino acids per gram of protein, soy powder 38.1, yuba 36.0, and soy milk only 29.9.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Food & function
Year
2023
Authors
Mengdi Li, Jing Wang, Jiayu Zhang, Ying Lv, Shuntang Guo, P. Van der Meeren
Related Content
Claims (6)
Tofu contains all essential amino acids in better proportions than most plant proteins, but the body absorbs fewer of those amino acids from tofu than from eggs, meat, or dairy.
The physical structure of soy foods determines how quickly digestive enzymes can break down their proteins during simulated digestion; denser structures slow enzyme access and reduce early protein breakdown.
Firm tofu releases more digestible protein than soymilk, reconstituted soymilk powder, or yuba when tested in a lab system simulating human digestion, and differences in how these products are processed affect how much protein becomes accessible.
Soy proteins with more tightly folded structures and more disulphide bonds release fewer free amino groups during digestion in laboratory tests because the dense structure blocks digestive enzymes from reaching their target sites.
Protein clumping in firm tofu and reconstituted soymilk powder is primarily caused by hydrogen bonds and hydrophobic interactions, while protein clumping in soymilk and yuba is primarily caused by disulphide bonds, showing that different food processing methods lead to different molecular stabilization patterns.
In laboratory tests, soy proteins that break apart more easily under chemical treatment are digested more completely by enzymes, because their structure is held together by weaker bonds rather than strong covalent links.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.