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DIAAS

DIAAS is a protein quality score based on ileal digestibility of individual amino acids in humans.

Definition

What 'DIAAS' means

The Digestible Indispensable Amino Acid Score (DIAAS), recommended by the FAO, evaluates protein quality by measuring true ileal digestibility of each essential amino acid. Unlike PDCAAS, DIAAS accounts for antinutritional factors and can exceed 1.0, offering a more accurate assessment for human nutrition.

Related terms

Iron AbsorptionPhytateOxalate
All glossary terms

In depth

The longer answer

DIAAS stands for Digestible Indispensable Amino Acid Score, a protein-quality metric introduced by the Food and Agriculture Organization in 2011. It measures how well a protein source meets human amino-acid requirements after digestion, using a scale where 1.0 or above indicates excellent quality. Consumers encounter DIAAS on nutrition labels or in discussions about plant versus animal protein, particularly when comparing foods like soy, peas, or beef.

DIAAS works by analyzing the true ileal digestibility of each essential amino acid in a food, using pigs or rats as models. Scores are calculated by comparing the digestible amino acid content to a reference pattern for human needs. For example, soy protein isolate scores around 0.90–1.0, while wheat gluten scores lower at about 0.25. Animal proteins like eggs or milk typically score above 1.0, reflecting their complete amino-acid profiles.

For shoppers, DIAAS offers a more precise protein-quality assessment than older metrics like PDCAAS, but it is not yet widely required on labels. A score below 1.0 does not mean a food is inadequate; combining complementary plant proteins, such as rice and beans, can achieve a complete amino-acid profile. However, DIAAS does not account for overall diet context or other nutrients, so it should be considered alongside total protein intake and variety.

At a glance

Quick facts

Quick facts — DIAAS
DetailWhat to know
Scale range0 to 1.0 or above
Top plant sourceSoy protein isolate, ~0.90–1.0
Animal comparisonEggs and milk score >1.0
Lowest common plantWheat gluten, ~0.25

In practice

What this means for you

  • Check ingredient lists for soy or pea protein isolates, which have high DIAAS scores among plant sources.
  • Combine grains with legumes in meals to boost overall protein quality without relying on animal products.
  • Ignore DIAAS for single foods if your diet includes a variety of plant proteins throughout the day.
  • Use DIAAS as a guide, not a rule; total protein intake matters more than perfect scores.

FAQ

Common questions

Is DIAAS better than PDCAAS for plant proteins?
Yes, DIAAS is more accurate because it measures digestibility at the end of the small intestine, not the whole tract. This gives lower scores for some plant proteins, but it also highlights that combining foods can compensate. For most people, eating a varied plant-based diet easily meets amino-acid needs.
Do I need to worry about DIAAS if I eat plant-based?
Not really, unless your diet is very limited. The human body pools amino acids from meals over the day, so a single low-DIAAS food is fine. Focus on eating a mix of legumes, grains, nuts, and seeds, and you will get enough of all essential amino acids without tracking scores.
Why do animal proteins score higher on DIAAS?
Animal proteins like eggs and milk have amino-acid profiles that closely match human needs and are highly digestible. Plant proteins often lack one or more essential amino acids in optimal amounts, and their fiber can reduce digestibility. However, this difference is easily overcome by eating a variety of plant foods.