The net protein utilisation (NPU) of which of the following foods is the highest?

RML Lucknow - 2021

Applied Nutrition & Dietetics

Easy

Appeared in: RML Lucknow - 2021

Explanation

Net Protein Utilisation (NPU) measures how efficiently the body uses dietary protein. It is the product of a protein's biological value and its digestibility.
Egg protein is considered the 'reference protein' because it contains all nine essential amino acids in proportions that are almost perfectly matched to human requirements.
Due to its ideal amino acid profile and high digestibility (over 97%), egg protein is retained and utilized by the body with very high efficiency, giving it an NPU value close to 100.
This makes egg the most efficiently utilized protein source among the given options.

Option A: Milk has a high biological value and is an excellent source of protein, but its NPU is lower than that of eggs (around 82-85).
Option B: Meat provides high-quality protein, but its NPU (around 70-80) is lower than both egg and milk. Digestibility can also vary.
Option C: Legumes have the lowest NPU among the options (around 40-65). This is because they are typically deficient in one or more essential amino acids (e.g., methionine) and contain anti-nutritional factors that can reduce protein digestibility.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Net Protein Utilisation (NPU) of common food sources as background academic context rather than a clinical decision trigger.
Nurses should recommend high-NPU foods like eggs and milk for patients with increased protein needs, such as those recovering from surgery, burns, or suffering from malnutrition, to promote efficient tissue repair and growth.
For vegetarian or vegan patients, nurses can provide education on protein complementation—combining foods like legumes and grains (e.g., beans and rice) to create a complete amino acid profile, thereby increasing the overall protein quality of the meal.
What if the patient has a known egg allergy? The nurse should then recommend the next best high-NPU food source that the patient can tolerate, such as milk or dairy products, and if necessary, well-cooked meat or fish.

How to Approach the Question

First, understand the question is asking for the food with the 'highest' Net Protein Utilisation (NPU).
Recall the definition of NPU: a measure of how efficiently the body uses a protein source. A higher NPU means less protein is wasted.
Systematically evaluate the protein quality of each option. Remember that animal proteins generally have higher quality than plant proteins.
Recall that egg is often used as the 'gold standard' or reference protein in nutrition because of its superior amino acid profile and high digestibility.
Compare the options: Egg > Milk > Meat > Legumes in terms of NPU.
Based on this hierarchy, conclude that egg has the highest NPU.

Concept Tested & Keywords

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E6 Parks TextBook of Preventive & Social Medicine part 2 — Subpart A (pp 1-232 of 464) pp. 165-167, 144-146