Protein

Protein is the most important component of the human body. Protein is present in all cells making up enzymes and structural components (tendons, ligaments), contractile proteins (muscle, including the heart), antibodies, hormonal, transport and storage proteins.

Protein is composed of chains of up to 20 amino acids. Nine amino acids are Protein is essential essential. That means they must be supplied with the food in sufficient amounts, because they cannot be made in the body. The essential amino acids are part of the proteins we eat. Therefore protein is an essential nutrient, without which we cannot survive.

A complete protein source contains all the essential amino acids; an incomplete protein source lacks one or more of the essential amino acids. More about amino acids here.

In the proteins the amino acid chains are folded in three dimensions in a very complex way. Thereby each protein achieves its unique structure and function. More about protein structure here.

Because the body has no protein storage provision it requires a daily supply of proteins to produce new proteins and to replace damaged proteins.

Sources

protein rich foods Meat, fish and eggs are sources of complete protein. Milk and milk-derived foods are also good sources.

Among the best vegetarian sources are soybeans, tofu and other soy-products, and legumes (pulses).

Daily intake

The recommended daily intake of good quality protein is 0.8-1.0 g/kg body weight. If you are physically very active, larger amounts - up to 2.5 g/kg - should be consumed to increase muscle mass, enable body repair, and cover energy needs.

A diet containing adequate amounts of amino acids (especially the essential) is particularly important during early development and maturation, pregnancy, lactation, or injury.

Generally, proteins derived from animal foods (meats, fish, poultry, cheese, eggs, yogurt, and milk) are complete, though gelatin is an exception. Except for quinoa or soybeans, proteins derived from plant foods (legumes, grains, and vegetables) tend to have less of one or more essential amino acid. Corn protein is low in the essential amino acids lysine and tryptophan. Here is a list of foods having the highest content of protein.

Deficiency

Protein deficiency leads to protein-energy malnutrition with loss of weight. The most severe form is known as Kwashiorkor, which is seen in children who develop edema, irritability, anorexia, skin ulcers, and an enlarged fatty liver. Mental retardation can also be a consequence of severe protein deficiency.

Excess

Provided you drink sufficient water you are unlikely to encounter problems with even very large intakes of protein. However, you should always ensure that your diet contains the other essential nutrients in sufficient amounts.

References: 1 , 2