DIAAS

DIAAS, or Digestible Indispensable Amino Acid Score, is a method for evaluating the quality of dietary protein by quantifying the amount of each indispensable amino acid that is truly digestible and available for metabolism in the human body. It was proposed in the early 2010s as an improvement on the approved PDCAAS method, using true ileal digestibility rather than fecal data and providing amino acid–specific scores rather than a single protein score.

Calculation of DIAAS involves several steps. For each indispensable amino acid, the true ileal digestibility is determined, and this value is applied to the amount of that amino acid present in a unit of protein to obtain the digestible content. This digestible content is then compared to a reference pattern for that amino acid, which varies by age group. The DIAAS for a protein source is the lowest ratio among all indispensable amino acids, expressed as a percentage. Reference patterns differ for groups such as infants, children, and adults, reflecting age-specific amino acid requirements.

Applications of DIAAS include assessment of the protein quality of individual foods, ingredients, and mixed diets, informing fortification strategies and nutrition labeling discussions. Plant-based proteins often have lower DIAAS due to limiting amino acids, while animal proteins typically score higher, though combinations can raise the overall DIAAS of vegetarian meals.

Limitations of the approach include the need for detailed ileal digestibility data, which are scarce for many foods and often derived from animal models. DIAAS remains primarily a research and policy tool rather than a universally adopted labeling standard, but it complements PDCAAS by providing amino acid–level evaluation and avoiding truncation at 100.