Manitoba Nephrology Nurse Practice Test

Which of the following best describes "negative nitrogen balance" related to protein metabolism?

1. Intake of protein exceeds output

2. Output of protein exceeds intake

3. Balanced protein intake

4. Low protein requirement

The correct answer is: Output of protein exceeds intake

Negative nitrogen balance occurs when the amount of nitrogen excreted from the body exceeds the amount ingested. This situation typically arises in conditions where the body is breaking down more muscle protein than it is synthesizing. It may be seen in illnesses, infections, or during periods of starvation, trauma, or recovery from surgery, where the body has increased protein needs but is not receiving adequate protein intake. In this context, when protein breakdown occurs at a greater rate than protein intake, the body loses nitrogen, which is a key component of amino acids that make up proteins. Thus, the output of protein, reflected by the amount of nitrogen lost (e.g., in urine), surpasses protein intake from dietary sources, leading to a negative nitrogen balance. This state can result in muscle wasting and overall body degradation if it persists over time. Therefore, the correct answer accurately captures the essence of negative nitrogen balance in protein metabolism.