Net protein utilization
The net protein utilization, or NPU, is the ratio of amino acid converted to proteins to the ratio of amino acids supplied. This figure is somewhat affected by the salvage of essential amino acids within the body, but is profoundly affected by the level of limiting amino acids within a foodstuff.
- 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))
As a value, NPU can range from 1 to 0, with a value of 1 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.
The Protein Digestibility Corrected Amino Acid Score is a more modern rating for determining protein quality.