Protein content and amino acid composition of commercially available plant-based protein isolates.
Level 5 - mechanism / opinion, no new human data
Bench laboratory analytical study evaluating amino acid profiles without human clinical intervention.
PubMed 30167963 · doi:10.1007/s00726-018-2640-5
What was done
The authors used ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) to measure essential amino acid (EAA) content and complete amino acid profiles of commercially available plant-based protein isolates (oat, lupin, wheat, hemp, microalgae, soy, brown rice, pea, corn, and potato). These were compared against animal-based proteins (milk, whey, caseinate, casein, egg) and human skeletal muscle protein.
What was found
Plant-based protein isolates exhibited lower total EAA contents (e.g., oat 21%, lupin 21%, wheat 22%) than animal-based proteins (whey 43%, milk 39%, casein 34%, egg 32%) and human skeletal muscle protein (38%). Leucine content varied widely across plant proteins, from 5.1% in hemp to 13.5% in corn protein (compared to 9.0% in milk, 7.0% in egg, and 7.6% in muscle protein). Methionine and lysine concentrations were lower in plant proteins (1.0 ± 0.3% and 3.6 ± 0.6%, respectively) compared to animal proteins (2.5 ± 0.1% and 7.0 ± 0.6%, respectively) and human muscle protein (2.0% and 7.8%, respectively).
Why it matters
This profiling quantifies the specific amino acid deficiencies (chiefly lysine and methionine) and lower total EAA densities of plant-based protein isolates relative to human muscle, providing a baseline to design targeted plant-plant or plant-animal protein blends to support muscle protein synthesis.
Limits
The study is restricted to in vitro chemical profiling and did not evaluate in vivo human digestion, postprandial amino acid absorption kinetics, or muscle protein synthesis rates. The abstract does not report the number of independent commercial batches or samples tested per source.
Cited by
- supports In whey protein powder, essential amino acids make up only approximately 45% of the total protein content.