DIAAS, Digestible Indispensable Amino Acid Score for assessing protein quality, will be fully endorsed upon completion of a programme of research to confirm the animal assay and to create a database of standard protein food values. In the interim, DIAAS can be estimated using published faecal crude protein digestibility values.
• The nutritional value of a dietary protein source relates to the delivery of indispensable amino acids to the body
• The content, pattern and bioavailability of indispensable amino acids determine the quality of the protein
• Methods for measuring protein quality assess the ability of a dietary protein to meet human requirements for indispensable amino acids1
• Digestible Indispensable Amino Acid Score (DIAAS) is a new assessment method that more accurately measures protein quality
• DIAAS was recommended by an FAO expert consultation on protein quality2
• DIAAS is based on the ileal digestible individual indispensable amino acids in the dietary protein relative to human reference amino acid requirement pattern
• True ileal digestibility of individual amino acids is the most accurate measurement of digestion and absorption of dietary amino acids
• The protein quality score is determined by the lowest ratio of digestible indispensable amino acid content to the corresponding indispensable amino acid in the reference pattern
• Scores may be greater than 1 (or 100%) if the protein contains a relatively high content of indispensable amino acids recognizing surplus amino acids in higher quality protein sources
• Values above 100% should not be truncated except where calculating DIAAS for protein or amino acid intakes for mixed diets or sole source foods2
• Dairy proteins are higher quality and have DIAAS values greater than 100%
• Milk powder has a DIAAS (%) of 1222
• Protein quality scores may be important in the future for adjusting/ informing/understanding the available protein or amino acid content of foods
• High protein quality foods such as dairy can be used to complement foods of poorer quality for cost effective and efficient use of available foods
• DIAAS will be fully endorsed upon completion of a programme of research to generate a database of indispensable amino acids ileal digestibility values for standard protein foods.