nitrogen balance
Last reviewed 03/2022
The nitrogen balance is a simple index of whether physiological protein requirements are being met. Urinary urea is taken as a rough indicator of protein degradation and loss from the body. Oral protein intake is quantified. Protein and urea are assumed to be rough indices of physiological nitrogen.
A negative nitrogen balance occurs when urinary nitrogen losses are greater than oral nitrogen intake. It may occur in:
- malnutrition e.g lack of essential amino acid - other amino acids which would have gone into the making of a new protein with the absent essential amino acid are instead degraded
- starvation
- adrenocortical steroid therapy
A positive nitrogen balance occurs when urinary losses are less than intake. It may occur in:
- active growth
- healing after systemic insult
Both positive and negative nitrogen balances are indications for dietary supplementation after a full assessment of which particular amino acids are deficient, with or without treatment of any underlying cause.