Tuesday, October 23, 2018
 FAO Proposes New Protein Quality Measurement  

By Dan Meyer

The Food and Agriculture Organization of United Nations (FAO) has released a report recommending a new, advanced method for assessing the quality of dietary proteins. The report, “Dietary protein quality evaluation in human nutrition,” recommends that the Digestible Indispensable Amino Acid Score (DIAAS) replace the Protein Digestibility Corrected Amino Acid Score (PDCAAS) as the preferred method of measuring protein quality. 


The report recommends that more data be developed to support full implementation, but in the interim, protein quality should be calculated using DIAAS values derived from fecal crude protein digestibility data. Under the current PDCAAS method, values are “truncated” to a maximum score of 1.00, even if scores derived are higher.


Using the DIAAS method, researchers are now able to differentiate protein sources by their ability to supply amino acids for use by the body. For example, the DIAAS method was able to demonstrate the higher bioavailability of dairy proteins when compared to plant-based protein sources. Data in the FAO report showed whole milk powder to have a DIAAS score of 1.22, higher than the DIAAS score of 0.64 for peas and 0.40 for wheat. 

The new DIAAS method is more accurate than PDCAAS in many ways.

PDCAAS calculates the digestibility of a protein by looking at the levels of protein remaining in faecal matter.  DIAAS samples come from the end of the intestine (or ileum) to provide a more accurate measure. Sampling from the ileum is more accurate because faeces also contain endogenous proteins such as digestive secretions, mucus, cells, and bacteria which impact the measurement.


Unlike PDCAAS, technology used in DIAAS can measure the digestion of individual amino acids, rather than just measuring digestion of crude protein. As a result, DIAAS is a more sensitive tool and paints a better picture of individual amino acid digestion.


The DIAAS method more accurately describes the value of protein ingredients because it doesn’t truncate scores to a maximum of 1.0. DIAAS recognizes the value of excess amino acids in a food or ingredient within the context of the entire diet, where an excess can make up for nutritionally incomplete proteins in other sources such as pulses and vegetables. Truncating to 1.0 has meant that superior sources of protein such as dairy have been nutritionally undervalued by PDCAAS.

PDCAAS rates protein sources against the amino acid reference pattern of a 2–5 year old child. DIAAS differentiates between the needs of infants and children with three reference patterns; 0–6 months, 6 months–3 years and 3 years+.


The FAO-endorsed DIAAS method gives a truer measurement of protein digestibility than PDCAAS, therefore providing a more accurate assessment of the nutritional quality of dietary protein sources.


To view the entire FAO report please visit: http://www.fao.org/ag/humannutrition/35978-02317b979a686a57aa4593304ffc17f06.pdf

  Protein Quality Score
MPC 1.30 1.0
WPI 1.25 1.0
Milk 1.22 1.0
WPC 1.10 1.0
Soy Protein Isolate 1.0 1.0
Pea Protein Conc. 0.94 0.94
Beans 0.64 0.7
Wheat 0.4 0.42


Dan Meyer is the Director of Technical Services at the American Dairy Products Institute and a member of the ADPI Center of Excellence team. He  handles all the technical matters relating to grade standards for dairy products and regulatory matters including food labeling, food safety issues, and allergens.

Posted on Friday, May 22, 2015 (Archive on Friday, May 29, 2015)
Posted by bholcomb@adpi.org  Contributed by bholcomb@adpi.org