The below mentioned article provides a short note on the Nitrogen Balance in Diet.
Nitrogen balance is defined as the quantitative difference between the nitrogen intake and the nitrogen output, both expressed in gms N/day. Intake means the nitrogen of the food and output means the excretion of nitrogen as urine, feces, milk, sweat, vomiting, menstrual fluid and loss of hair.
Positive nitrogen balance exists when intake exceeds output. This condition occurs whenever new tissue is synthesized such as during growth of the young and in pregnancy. In negative nitrogen balance, the output exceeds the intake.
The condition occurs in inadequate intake of protein (fasting, diseases of the gastrointestinal tract), in accelerated catabolism of tissue protein (fevers, infections, wasting diseases and trauma) and in the absence of “essential” amino acid from the diet.
It is concluded from the above discussion that nitrogen equilibrium [intake = output] is maintained only in the adult organisms and only in the absence of the abnormal conditions.
An “adequate diet” contains all requirements for minerals and vitamins, the protein of the diet is of high “biological value” and is administered at a sufficiently high level; other caloric needs are met satisfactorily by the carbohydrate and fat of the diet.
A minimum amount of dietary carbohydrate (5 grams/100 calories) is required for the maintenance of nitrogen equilibrium, independently of the adequacy of the energy provision from fat and protein. This is referred to as the “protein-sparing action” of carbohydrate.
Under these circumstances, the nitrogen output equals the intake. An increase or decrease in the intake is followed by a corresponding adjustment in the output, so that nitrogen equilibrium is established at a new level. There is no marked tendency for storage of surplus nitrogen.