Evidence-Based Nutrient Recommendations

Protein Quality Scoring


by Jack Norris, RD

Discussions about protein needs tend to revolve around nitrogen balance studies and protein quality scores.

One of the earliest ways to assess protein quality was the protein efficiency ratio (PER) which is based on the growth of rats. In 1989, the Food and Agriculture Organization (FAO) recommended the protein digestibility–corrected amino acid score (PDCAAS) which is based on the protein needs of humans. In 2011, the FAO switched to recommending the digestible indispensable amino acid score (DIAAS) which is based on the digestibility of individual amino acids rather than entire proteins.

Because protein quality scoring lacks standardization with many gaps in the information, Vegan Health emphasizes protein balance studies in assessing the protein needs of vegans.

But because protein quality scoring is a significant part of the conversation around protein, I’ve added Appendix A: Protein Quality Scoring to our Protein: Research article to provide an explanation of the PDCAAS and DIAAS scoring systems and a critical analysis with regard to their application to plant-based diets.

If you’re interested in protein quality scoring with respect to plant-based diets, you might find the Appendix interesting.

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