Food and proteins

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Which foods are the richest in protein?

Proteins are the building blocks of living organisms. However, this peculiar function, called plastic, is not the only one. In fact, proteins are also responsible for the synthesis of hormones, enzymes and tissues (especially muscle).

In conditions of low energy intake, proteins obtained from food or from muscle catabolism can be used by the liver to supply energy to the body.

From a chemical point of view, proteins are macromolecules made up of 22 fundamental units called AMINO ACIDS, which, like many rings, join together to form a long chain.

Eight of these amino acids are essential as the body cannot synthesize them fast enough to meet metabolic demands. These amino acids (leucine, isoleucine, lysine, methionine, valine, threonine, phenylalanine, tryptophan) must therefore be introduced with food, in order to avoid specific nutritional deficiencies. In the first two years of life, two other amino acids become essential, respectively called arginine and histidine.

Not all proteins are created equal

"High biological value" proteins can be found in foods of animal origin: it simply means that these foods contain all the "essential" amino acids in the right proportions and quantities.

The proteins present in plant foods, on the other hand, have a worse amino acid profile, as they are deficient in one or more "essential" amino acids. However, this deficit can be easily filled by combining plant foods of different origins (such as the classic pasta and beans). See: vegetable proteins.

QUALITY OF PROTEINS

Three parameters are used to evaluate the quality of proteins present in food:

CUD (digestive utilization coefficient): is given by the ratio between absorbed nitrogen and ingested nitrogen (Na / Ni): the CUD is high for proteins of animal origin, lower for proteins of vegetable origin;

PER (protein efficiency ratio): based on the study of the growth curves of batches of animals fed with proteins: it indicates the gain in body weight for each gram of ingested protein;

NPU (net protein utilization): expresses the digestibility and biological value of the protein.

How Much Protein?

The recommended dietary protein intake is inversely proportional to age:

2 g / kg / day in the newborn

1.5 g/kg/die a 5 anni

1-1.2 g / kg / day in adolescence and adulthood

2/3 of these proteins should come from food of animal origin and 1/3 from food of plant origin.

EXCESS OF PROTEINS: correlates with overweight and greater renal and hepatic effort. An excess of animal-based proteins associated with high amounts of saturated fat (beef, pork or other lipid-rich red meat) is one of the risk factors for colon cancer and numerous other diseases. See: Diet and cancer

Protein-rich foods

NB cooking food considerably decreases the biological value of proteins