Infographic: Protein Quality in Medical Nutrition

The infographic below explains protein quality and demonstrates the protein quality of dairy and plant proteins used in medical nutrition assessed using PDCAAS (Protein Digestibility Corrected Amino Acid Score).


Protein is a crucial macronutrient that is essential for many biological processes including maintenance of muscle mass and function, production of liver proteins and gut digestive enzymes, wound healing, and immune function‌1 - 4.

Protein is made of building blocks called amino acids

Dietary amino acids can be categorized as essential (cannot be synthesized in the body) and non-essential (can be synthesized in the body)5,6.

In certain diseases the ability to synthesize non-essential amino acids is compromised, and these amino acids become conditionally essential4,7-12.

Dairy and plant proteins both contain essential and non-essential amino acids

Generally, dairy proteins are richer in essential amino acids and plant proteins are richer in some non-essential amino acids, including those that become conditionally essential in disease. However, dairy, certain individual plant sources, and blends of different protein sources, can meet daily requirements for all essential amino acids

There are differences in amino acid metabolism in health compared to disease, resulting in different amino acid requirements13-14.

In conditions where protein intake is inadequate, ensuring high protein quality becomes even more important.

Ensuring medical nutrition products provide the right protein quantity and quality is important to improve outcomes such as wound healing, strength, and physical performance2,15.


Protein quality is the capacity of a protein source to meet amino acid requirements to satisfy metabolic needs5,6.

Protein Digestibility Corrected Amino Acid Score (PDCAAS) is a method to assess protein quality that is recognized by the Food and Agriculture Organization and World Health Organization5,6.


PDCAAS of Dairy and Plant Proteins

Protein Isolate PDCAAS*
Cassein 1,4
Whey 1,0
Soy 1,1
Pea 0,9

*Calculated using average digestibility of 98,5%16-18 and FAO 2013 amino acid requirement references for adults6.
PDCAAS scores are normally truncated to 1, however, untruncated values have been reported to reflect true differences between protein sources.

A protein source with a PDCAAS of 1 is considered high quality19.

Tube and ONS products with dairy, plant, or blends of different protein sources can achieve a PDCAAS of 1, indicating high protein quality.


Protein from both dairy and plant sources can meet standards for protein quality and be considered high quality, and therefore meet the needs of patients requiring medical nutrition.

Ensuring adequate intake of high quality protein will have positive impacts on outcomes such as infections, wound healing, strength, and physical performance2,15.

Call to Action

Be confident that your patient’s needs can be met with medical nutrition products containing different sources of protein, including plant protein.

Work together with your patient to pick the tube feed or ONS that meets their lifestyle preferences and medical needs


  1. Ochoa Gautier et al. Nutr Clin Pract. 2017;32:6S-14S
  2. Hurt et al. Nutr Clin Pract. 2017;32:142S-51S.
  3. Rostom & Shine. Surgery. 2018;36:153-158.
  4. Hou et al. Exp Biol Med. 2015;240:997-1007.
  5. Report of a joint FAO/WHO/UNU expert consultation. 2007.
  6. Report of an FAO Expert Consultation. 2013.
  7. Van der Meij et al. Int. J. Radiat. Biol. 2019; 95:4, 480-492.
  8. Mast et al. Nutr Res Reviews. 2018;31.2:179-92.
  9. Morris et al. Nutr Clin Pract. 2017;32.1:30S-47S.
  10. Alves et al. Nutrients. 2019;11.6:1356.
  11. Wu et al. Amino Acids. 2013;45.3:463-77.
  12. McPerson et al. Curr Opin Clin Nutr Metab Care. 2011;14.6:562-8.
  13. Jonker et al. Br. J. Nutr. 2012;108.S2:S139-48.
  14. Weijs et al. Crit care. 2014;18.6:1-3.
  15. Bauer et al. J Am Med Dir Assoc. 2013;14.8: 542-559.
  16. Report of the Joint FAO/WHO Expert Consultation. 1991.
  17. Rutherfurd et al. J Nutr. 2015;145:372-9.
  18. Yang et al. Agro Food Ind Hi Tech. 2012;23:8-10.
  19. Huang et al. Crit Rev Food Sci Nutr. 2018;58.15:2673-8

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