Net protein utilization: Difference between revisions

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{{Short description|Percentage of ingested nitrogen that is retained in the body}}

The '''net protein utilization''', or '''NPU''', is the percentage of ingested nitrogen that is retained in the body. It is used to determine the nutritional efficiency of protein in the diet,<ref name=EFSA2012>{{cite journal |title=Scientific Opinion on Dietary Reference Values for protein: Dietary Reference Values for protein |journal=EFSA Journal |date=February 2012 |volume=10 |issue=2 |pages=2557 |doi=10.2903/j.efsa.2012.2557}}</ref>{{rp|p=11}} that is, it is used as a measure of "protein quality" for human nutritional purposes.<ref>[https://labdoor.com/article/protein-quality-the-4-most-important-metrics Protein Quality–The 4 Most Important Metrics]</ref>

The '''net protein utilization''' ('''NPU''') is the percentage of ingested [[nitrogen]] that is retained in the body.

==Rating==

The '''net protein utilization''', or '''NPU''', is the percentage of ingested nitrogen that is retained in the body. It is used to determine the nutritional efficiency of protein in the diet,<ref name=EFSA2012>{{cite journal |title=Scientific Opinion on Dietary Reference Values for protein: Dietary Reference Values for protein |journal=EFSA Journal |date=February 2012 |volume=10 |issue=2 |pages=2557 |doi=10.2903/j.efsa.2012.2557|s2cid=139100064 |hdl=2434/257730 |hdl-access=free }}</ref>{{rp|p=11}} that is, it is used as a measure of "protein quality" for human nutritional purposes.<ref>[https://labdoor.com/article/protein-quality-the-4-most-important-metrics 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 [[Eggegg (food)|egg]]s or [[milk]], rate as 1 on an NPU chart.

Experimentally, this value can be determined by determining [[diet (nutrition)|diet]]ary protein intake and then measuring [[nitrogen]] [[excretion]]. One formula for apparent NPU is:<ref>{{cite journal |last1=Blackburn |first1=GL |last2=Bistrian |first2=BR |last3=Maini |first3=BS |last4=Schlamm |first4=HT |last5=Smith |first5=MF |title=Nutritional and metabolic assessment of the hospitalized patient. |journal=JPEN. Journal of parenteralParenteral and enteralEnteral nutritionNutrition |date=1977 |volume=1 |issue=1 |pages=11-2211–22 |doi=10.1177/014860717700100101 |pmid=98649}}</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)}

ANPU closely related quantity, theand [[biological value]] (BV), is the percentage of absorbed nitrogen that is retained in the body.<ref name=EFSA2012 />{{rp|p=11}} NPU and BV both measure nitrogen retention, however,; the difference is that biological value is calculated from nitrogen ''absorbed'', whereas net protein utilization is from nitrogen ''ingested''.<ref>{{cite journal |last1=Hoffman |first1=JR |last2=Falvo |first2=MJ |title=Protein - Which is Best? |journal=Journal of sportsSports scienceScience & medicineMedicine |date=September 2004 |volume=3 |issue=3 |pages=118-30118–30 |pmid=24482589|pmc=3905294 }}</ref> BVAnother closely related quantity is calculatedthe asnet postprandial protein utilization (NPPU), which is the productmaximum ofpotential NPU andof a dietary protein source under ideal digestibilityconditions.<ref name=EFSA2012 />{{rp|p=1112}}

NPU values can be either true or apparent, depending on whether the loss of endogenous nitrogen is taken into account or not; this is critical for precisely determining the efficiency of dietary protein utilization and the quality of different dietary protein sources.<ref name=EFSA2012 />{{rp|p=12}} The true NPU can be calculated as follows:<ref name=EFSA2012 />{{rp|p=12}}

<math>True NPU = total N_{ingested} - {\frac{(total N_{feces} - endogenous N_{feces}) + (total N_{urine} - endogenous N_{urine})}{total N_{ingested}}}</math>

A closely related quantity, the [[biological value]] (BV), is the percentage of absorbed nitrogen that is retained in the body.<ref name=EFSA2012 />{{rp|p=11}} NPU and BV both measure nitrogen retention, however, the difference is that biological value is calculated from nitrogen ''absorbed'', whereas net protein utilization is from nitrogen ''ingested''.<ref>{{cite journal |last1=Hoffman |first1=JR |last2=Falvo |first2=MJ |title=Protein - Which is Best? |journal=Journal of sports science & medicine |date=September 2004 |volume=3 |issue=3 |pages=118-30 |pmid=24482589}}</ref> BV is calculated as the product of NPU and digestibility.<ref name=EFSA2012 />{{rp|p=11}}

Another closely related quantity is the net postprandial protein utilization (NPPU), which is the maximum potential NPU of a dietary protein source when determined in optimal, controlled conditions in healthy adults. To determine the NPPU of a dietary protein source, true dietary protein nitrogen retention is directly measured in the postprandial phase using ¹⁵N-labeled dietary proteins. This is done because the postprandial phase is critical for dietary protein utilization. The measurement of the immediate retention of dietary nitrogen following meal ingestion is a reliable way to assess protein nutritional efficiency.<ref name=EFSA2012 />{{rp|p=12}}

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.

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==See also==

* [[Biological value]]

* [[Protein efficiency ratio]]

* [[Nitrogen balance]]

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==References==

{{reflist}}

[[Category:Amino acids]]