Net protein utilization
Template:Short description The net protein utilization (NPU) is the percentage of ingested nitrogen that is retained in the body.
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[edit]It is used to determine the nutritional efficiency of protein in the diet,<ref name=EFSA2012>Template:Cite journal</ref>Template:Rp that is, it is used as a measure of "protein quality" for human nutritional purposes.<ref>Protein Quality–The 4 Most Important Metrics</ref>
As a value, NPU can range from 0 to 1 (or 100), with a value of 1 (or 100) indicating 100% utilization of dietary nitrogen as protein and a value of 0 an indication that none of the nitrogen supplied was converted to protein.
Certain foodstuffs, such as eggs or milk, rate as 1 on an NPU chart.
Experimentally, this value can be determined by determining dietary protein intake and then measuring nitrogen excretion. One formula for apparent NPU is:<ref>Template:Cite journal</ref>
- NPU = {0.16 × (24 hour protein intake in grams)} - {(24 hour urinary urea nitrogen) + 2} - {0.1 × (ideal body weight in kilograms)} / {0.16 × (24 hour protein intake in grams)}
NPU and biological value (BV) both measure nitrogen retention; the difference is that biological value is calculated from nitrogen absorbed, whereas net protein utilization is from nitrogen ingested.<ref>Template:Cite journal</ref> Another closely related quantity is the net postprandial protein utilization (NPPU), which is the maximum potential NPU of a dietary protein source under ideal conditions.<ref name=EFSA2012 />Template:Rp
The Protein Digestibility Corrected Amino Acid Score (PDCAAS) is a more modern rating for determining protein quality, and the current ranking standard used by the FDA.
The Digestible Indispensable Amino Acid Score (DIAAS) is a protein quality method, proposed in March 2013 by the Food and Agriculture Organization<ref>Template:Cite web</ref> to replace the current protein ranking standard, the Protein Digestibility Corrected Amino Acid Score (PDCAAS). The proposition is contested, however, due to lack of data.<ref>Template:Cite web</ref>