Protein as a Source of Energy

After the needs of the tissues are satisfied, there may be a surplus of ingested protein products for which the body has no immediate specific use. The amino acids not required are taken up by the liver and deaminated. The amino group is removed and converted into urea, which is excreted by the kidneys. The remainder of the molecule is then available, either for direct energy production or for conversion to CHO or fat.

Protein Storage

The amount of protein in the body is not constant, but depends to some extent on the protein content of the food intake. A well-nourished human adult contains about 12 kg protein, of which he can lose about 3 kg without serious loss of function or threat to life.

Amino acids are wasted, and are not used for their specific needs whenever there is:

• Not enough energy from carbohydrate or fat
• Not enough essential amino acids
• Excessive protein intake beyond daily needs
• Excess amino acids from “amino acid supplements”.

Factors that must be supplied by food intake to enable the synthesis of protein:

• All essential amino acids simultaneously and in the proper amounts
• An adequate total amount of protein to enable non essential amino acid production
• Adequate energy yielding carbohydrate and fat to spare the protein
• Amino acids can be metabolised to protein, glucose, nitrogen + energy or fat. They will be metabolised to protein only if sufficient energy is present from other sources and if all of the essential amino acids are present simultaneously.

How Much Protein Is Needed?

It is essential that the minimum amount of dietary protein required by a normal healthy human is about 0.35gm/kg of body weight. The recommended dietary intake is set at minimum of 1gm/kg of body weight.