Protein requirements for an adult is about 12-15% of the total energy value of the diet, which corresponds to about 1.2-1.6 grams per kilogram of body weight per day. Sports increase this need. One gram of protein contains about 4 calories.
In the gastrointestinal tract of the protein is cleaved to the free amino acids are absorbed into the blood and body tissues are then used for the construction of cellular structures, hormones, enzymes.
The amount of free amino acids in the blood is maintained at a constant level by the body. If diet lacking in proteins in order to maintain a constant blood level of amino acids are destroyed tissue.
In particular this applies to passive muscle, which is the main reason for the loss of muscle mass at the wrong weight loss.
Part of the amino acids our body can synthesize itself. They are called “replaceable”. Eight amino acids the body can not synthesize. They are called “essential” or “with essential.” These include threonine, valine, leucine, isoleucine, methionine, phenylalanine, tryptophan, lysine. They must necessarily come from food. The need for all essential amino acids in the same human.
The quality of protein in the product is determined by the composition of amino acids. The ideal is called the composition corresponding to human needs. For products with good quality protein include egg, milk, meat, fish.
These products contain animal proteins. Product in which little or no essential amino acids at least one of them can not be a source of quality protein. These products include grain and bean products.
Contents ideal protein amino acids, mg / g
|Methionine + cystine||35|
|Phenylalanine + tyrosine||60|
A balanced diet must contain not less than 50% animal protein as vegetable proteins do not contain a sufficient amount of essential amino acids.