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Nitrogen balance

Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

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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.


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