All are TRUE regarding Net Protein Utilisation, except?
**Net Protein Utilisation (NPU)**
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### Core Concept
Net Protein Utilisation (NPU) is a measure of the proportion of absorbed dietary protein that is retained by the body for growth, maintenance, or storage. It is calculated as the ratio of amino acid retention to amino acid intake. NPU is an important concept in nutrition, as it helps to evaluate the quality of dietary protein sources.
### Why the Correct Answer is Right
NPU is influenced by factors such as the digestibility of protein, the availability of amino acids, and the body's demand for protein. The NPU of a protein source can be affected by factors like heat processing, which can denature proteins and reduce their digestibility. Additionally, NPU can vary across different protein sources, such as animal-based proteins like egg and meat, which tend to have higher NPU values compared to plant-based proteins like legumes and grains.
### Why Each Wrong Option is Incorrect
**Option A:** NPU is not affected by the type of amino acid present in the protein source. This is incorrect because the availability of essential amino acids (EAAs) is a critical factor in determining NPU. EAAs like leucine, isoleucine, and valine are particularly important, as they cannot be synthesized by the body and must be obtained through the diet.
**Option B:** NPU is a measure of protein quality. This is correct, but not the statement we are looking for.
**Option C:** NPU is not influenced by the caloric content of the diet. This is incorrect because the body's energy requirements can impact protein metabolism and affect NPU. When energy intake is low, the body may prioritize energy conservation over protein synthesis, leading to reduced NPU.
**Option D:** NPU is a measure of protein synthesis. This is incorrect because NPU specifically refers to the proportion of absorbed protein that is retained by the body, not the rate of protein synthesis.
### Clinical Pearl / High-Yield Fact
A high NPU value is often associated with animal-based protein sources, which tend to have a more balanced amino acid profile and are more easily digested by the body.
### Correct Answer: C. NPU is not influenced by the caloric content of the diet.