Which statement about nitrogen balance measurement is true?

Which statement about nitrogen balance measurement is true?

• A. It is determined by measuring urine urea
• B. It is determined by measuring urine nitrogen concentration
• C. It is determined by measuring stool output
• D. It is determined by measuring dietary intake alone

Answer: (A)

Nitrogen balance is the difference between what you take in (from dietary protein) and what you lose (through urine, feces, sweat, and skin). The largest and most practical portion of nitrogen loss is in urine, mainly as urea. Because urea carries most of the urinary nitrogen, measuring urinary urea excretion provides the best estimate of nitrogen losses and thus allows calculation of balance when you compare it to nitrogen intake. That’s why this statement is the most accurate: urinary urea excretion serves as the key proxy for total nitrogen loss. Simply measuring urine nitrogen concentration doesn’t give total excretion, measuring stool output misses the main urinary loss, and relying on dietary intake alone ignores the losses that determine balance.

Nitrogen balance is the difference between what you take in (from dietary protein) and what you lose (through urine, feces, sweat, and skin). The largest and most practical portion of nitrogen loss is in urine, mainly as urea. Because urea carries most of the urinary nitrogen, measuring urinary urea excretion provides the best estimate of nitrogen losses and thus allows calculation of balance when you compare it to nitrogen intake. That’s why this statement is the most accurate: urinary urea excretion serves as the key proxy for total nitrogen loss. Simply measuring urine nitrogen concentration doesn’t give total excretion, measuring stool output misses the main urinary loss, and relying on dietary intake alone ignores the losses that determine balance.