Nitrogen Balance in Nutrition - Medicospot

 Definition

Nitrogen balance are calculations that estimate the amount of catabolism. The patients intake of protein is subtracted from nitrogen output through urinary losses. In simple word, the balance in which the amount of nitrogen taken is excreted in same amount from the body is called Nitrogen balance. 

Formula

Nitrogen balance = Nitrogen intake - Nitrogen loss

Nitrogen intake = Protein intake / 6.25

Nitrogen loss = Urinary urea  nitrogen + 4

Example:

For example,  a patient receiving 50g of protein per day in an enteral tube feeding is getting 8g of nitrogen per day ( 50g / 6.25 = 8). If that individual nitrogen losses are 10g per 24 hours then the patient nitrogen balance is -2g/24 hours. 

Main source

The main source of nitrogen is amino acid . The nitrogen excrete from the body in the form of urea.

Types

There are two types of Nitrogen balance 

1. Positive Nitrogen Balance : 

In positive nitrogen balance, intake of nitrogen is greater than excretion. 

It usually occur in pregnancy, starvation and childhood.

Increasing protein in the enteral tube feeding to more than 62.5g protein per day will result in a  positive nitrogen balance. 

2. Negative Nitrogen Balance 

In negative nitrogen balance, nitrogen intake is less than excretion. 

It usually occur in stress, cancer and trauma. 

Nitrogen excrete in the form of urea by degrading protein.

However, nitrogen balance calculation is not accurate with renal failure. Other sources of nitrogen such as blood products as well a the loss of nitrogen from wounds, stool, nasogastric suction and bleeding, must also be taken into account when calculating nitrogen balance. The 4g of insensible nitrogen loss may not be an accurate estimate and could affect the accuracy of the result. Measurement of urinary urea nitrogen requires an accurate 24 hour urine collection. Accurate 24 hours urine collection is very difficult to obtain in clinical settings, even in patients who have urinary catheters in place. Because of this and the expense associated with measurement of urinary urea nitrogen, routine use of nitrogen balance cannot be recommended in clinical practice.