does not distinguish between the contributions of a protein that
provides adequate vs. excessive amounts of particular amino
acids, the method relies only on a single reference pattern for
2–5 year olds), consensus among experts for a method to replace
PDCAAS has not yet been achieved. PDCAAS is currently
used in the United States to evaluate and support a protein nutrient content claim that a particular food is a “good” or “excellent
source” of protein. Figure 1 (page 111) provides PDCAAS
values for common protein-containing ingredients and foods.
Biological Value (BV), which compares the amount of
nitrogen retained to the amount of nitrogen absorbed while on
a specific test diet, is not used not used by regulatory agencies
but is popular in the sports market segment. A criticism of this
method is that BV is measured when the protein content of a
diet is below a requirement, and differences seen often disappear
when protein is fed at levels above or close to the requirement.
More recently, the Digestible Indispensable Amino Acid
Score (DIAAS) has been proposed. Its advocates recommend
that different amino acid reference patterns and ileal digestibil-
ity be used to assess amino acid bioavailability. Other methods
using stable isotope tracers have also been proposed. These
include the Indicator Amino Acid Oxidation Method, Postpran-
dial Protein Utilization, and Net Postprandial Protein Utiliza-
tion. These newer methods are not generally accepted and lack
regulatory adoption. Greater consensus is needed before these
can be used for routine food evaluation.
To achieve consensus, further evaluation is needed to determine the most biologically relevant, reproducible, cost-effective
method that can be widely and practically implemented. An
ideal method for the food industry would be one that accurately
reflects the ability of a food protein to meet human nutritional
needs, is easily understood by the food industry as well as by
health practitioners, and is economical to implement within a
reasonable period of time. Collaborative studies would need to
be conducted to demonstrate excellent repeatability within a
laboratory and reproducibility between laboratories. Increased
interest in this topic led to a full session at the AOCS Annual
Meeting in May 2014 that was devoted to the topic “Assessment
of protein nutritional quality.” While the protein quality debate
pushes on, PDCAAS continues to be the approved protein
quality methodology for regulatory purposes.
Glenna Hughes is a senior research scientist in the global
nutrition group at DuPont Nutrition & Health. She manages
external and internal research studies exploring the health
benefits of soy protein and manages the protein quality program. She can be contacted at email@example.com.
• FAO/WHO, Protein quality evaluation; FAO Food and
Nutrition Paper 51, Rome, Italy, 1991.
• Millward, D. J., Amino acid scoring patterns for protein
quality assessment, Br. J. Nutr. 108: S31–S43, 2012.
• Tome, D., et al., Current issues in determining dietary
protein quality and metabolic utilization, Eur. J. Clin.
Nutr. 68: 537–8, 2014.
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