•It has been found that excess or deficiency of certain nutrients affects the requirements of some other nutrients.
•Protein-Energy Interrelationship:
•Restriction of calorie intake causes breakdown of tissue proteins and negative nitrogen balance. If the calorie restriction is severe, the animal body is depleted of depot fat and catabolism of tissue proteins continues, eventually leading to the death of the animal.
•When the calorie restriction was 50% of the requirement, about 74% of the dietary protein was oxidized and used to meet energy needs and only 20% of the dietary protein was used to meet the protein needs of the body.
•Effect of Calorie Restriction on Protein Content of the Body
•Both protein contents of the body and liver are reduced when the calorie intake is restricted to 50% when the protein intake was about 1g/day/rat.
•Effect of Carbohydrate and Fat on Protein Metabolism
•A difference in the effects of equicalorie amounts of carbohydrates and fats as a source of calories on protein metabolism has been demonstrated in fasted rats (Table).
•Effect of Feeding Carbohydrate or Fat on Urinary N Output in Fasting Adult Rats
• _____________________________________________________
• Diet during 24 hr. Urinary N (mg/24 hrs.)
• Fasted 135
• Glucose (12 g) 93
• Olive oil (5 ml) 111
•Administration of carbohydrate brought about a marked reduction in the catabolism of tissue proteins as seen by decrease in the urinary N while equicalorie quantity of fat was less effective. This observation is known as “Protein Sparing Action” of carbohydrates.
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