Determination of Digestible Indispensable Amino Acid Scores for Plant Proteins and Skim Milk Powder Measured in Pigs.
Level 5 - mechanism / opinion, no new human data
Animal model (pig) and in vitro digestion study
PubMed 40075933 · doi:10.3390/ani15050650
What was done
Twelve barrows (initial body weight 28.4 kg) fitted with distal ileal T-cannulas were assigned to a replicated 6 × 5 incomplete Latin square design across five periods. Standardized ileal digestibility (SID) of amino acids was measured for five sole-source protein diets (white rice, wheat, pea protein concentrate, soy protein isolate, and skim milk powder) and a nitrogen-free diet to quantify basal endogenous losses. Digestible indispensable amino acid scores (DIAAS) were calculated for infants, children, and adults, and compared with in vitro ileal disappearance (IVID) of crude protein using flask and Daisy II incubator methods.
What was found
DIAAS values across infants, children, and adults were: - White rice: 42, 50, and 60 - Wheat: 46, 56, and 66 - Pea protein concentrate: 47, 58, and 69 - Soy protein isolate: 61, 74, and 87 - Skim milk powder: 82, 112, and 131 IVID of crude protein was significantly greater for skim milk powder than for all plant sources (p < 0.05). DIAAS estimates derived from in vitro disappearance were reported to be similar to in vivo pig-derived scores.
Why it matters
These data benchmark the protein quality of single plant sources against dairy protein, showing that none of the tested plant proteins met complete indispensable amino acid requirements on their own (DIAAS < 100), reinforcing the need to blend plant sources in human diets.
Limits
Findings rely on a growing pig surrogate model and in vitro digestion rather than direct human clinical trials. The sample size was small (12 male pigs), and the abstract does not report variance estimates or confidence intervals for individual DIAAS values.
Cited by
- supports Based on the Digestible Indispensable Amino Acid Score (DIAAS), animal protein possesses the highest protein digestibility and protein quality found in nature.