Understanding Protein Quality: PDCAAS Scores

NovoNutrients announced that it had successfully produced ‘beef-quality’ protein from CO2. This document provides additional detail to that announcement, describing the approach and data used to reach those conclusions, which include a PDCAAS of 1.14 for the NovoNutrients protein ingredient.

Protein Digestibility Corrected Amino Acid Score (PDCAAS) is a measure developed by the Food and Agriculture Organization of the United Nations to quantify how much of the amino acids present in a food will be absorbed by the body through the digestive tract. It relies on two key components, (1) amino acid composition, specifically looking at each essential amino acid (EAA), and (2) digestibility, or how much of the protein will be broken down and metabolized. The formula for PDCAAS is:

(amount of limiting amino acid [mg/g protein]) / (FAO standard of limiting amino acid [mg/g protein]) * digestibility

The FAO sets a standard dietary intake reference pattern for how much of each EAA is required to support a minimum of healthy bodily functioning. The EAA that is least abundant relative to these guidelines (the lowest ratio) is the limiting amino acid.

Often, PDCAAS is calculated using the standard requirements pattern for children aged <1 year, who require the highest amount of EAAs. However, as the vast majority of consumers of NovoNutrients protein ingredient will be three years old or older, we use Age 3-10 as our benchmark pattern for dietary requirements, which is a higher bar than if we were to use the adult standard.

Digestibility can be determined in laboratory settings (in vitro) or in live organism analysis (in vivo). NovoNutrients uses in vitro testing to determine digestibility. Possible values range from 0 (completely indigestible, all protein excreted as waste) to 1 (completely digestible, no protein excreted as waste). The sample of our protein tested by Medallion Labs was found to have a digestibility score of 1.

We calculated our modified PDCAAS using average EAA composition from multiple (n=3) protein samples, and determined the following results. In our case, as with many isolated proteins and whole foods, Lysine (Lys) was found to be the limiting amino acid.

EAA values for NovoNutrients protein compared to FAO reference levels for ages 3-10, set forth in the Dietary Protein Quality Evaluation in Human Nutrition Expert Consultation (2011).

We then multiplied the ratio of our limiting amino acid, Lysine, by our digestibility factor, 1. Thus:

PDCAAS = (amount of limiting amino acid [mg/g protein]) / (FAO standard of limiting amino acid [mg/g protein]) * digestibility —>

(54.76 mg/g protein) / (48 mg/g protein) x 1 = 1.14 * 1 = 1.14

A PDCAAS of 1 or higher indicates that the protein supplies 100% or more of the recommended daily intake of EAAs.

Some presentations of PDCAAS truncate scores higher than 1.0 to 1. We present the untruncated values.

The score for NovoNutrients protein ingredient is equal to that of beef (1.14) and is superior to those of leading animal and plant proteins, including chicken breast (1.01), soya protein isolate (0.93), and pea protein concentrate (0.75). Those and other reference values are shown in Exhibit 1, on the following page.

Exhibit 1

Based on Burd NA, Beals JW, Martinez IG, Salvador AF, Skinner SK. Food-First Approach to Enhance the Regulation of Post-exercise Skeletal Muscle Protein Synthesis and Remodeling. Sports Med. 2019;49(Suppl 1):59-68. doi:10.1007/s40279-018-1009-y

We excerpt from the article’s Table 1, focusing on protein digestibility-corrected amino acid score (PDCASS) for isolated proteins and whole foods:

Notes from the article

Only values that used the scoring patterns for children older than 3 years, adolescents, and adults were selected

1. Values for DIAAS were calculated from the ileal digestibility of amino acids
2. Values for PDCAAS were calculated from the total tract digestibility of crude protein
3. All values for DIAAS and PDCAAS were selected in humans, if available, growing pigs, or in growing rats in that order
4. Measured in humans
5. Measured in pigs
6. Measured in rats