PDCAAS vs DIAAS: how protein quality is measured
Two scores, one question: how much of a food’s protein can your body actually use?
September 23, 2026 · 1 min read
Grams of protein on a label tell you quantity. Protein quality scores tell you how much of that protein your body can actually use to build tissue.
PDCAAS
The Protein Digestibility-Corrected Amino Acid Score (PDCAAS) compares a food’s essential amino acids to human requirements and adjusts for overall digestibility. It is capped at 1.0, so whey, egg, milk and soy all score 1.0 or close to it — which hides real differences between top-quality proteins.
DIAAS
The Digestible Indispensable Amino Acid Score (DIAAS), recommended by the FAO in 2013, measures digestibility of each amino acid at the end of the small intestine and is not capped. Scores of 100% or more indicate excellent quality; 75–99% high quality; below 75% means the protein should be combined with others.
How to use the scores
- Use them to compare foods — not to judge a whole diet.
- Low-scoring foods still contribute; pair them to cover their limiting amino acid.
- Filter and sort by PDCAAS or DIAAS in the ProteinMD Encyclopedia.