Food and proteins

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are the building blocks of living organisms. This peculiar function, called plastic, however, is not the only one. Proteins are in fact 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.

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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 is unable to synthesize them at sufficient speed to meet metabolic requirements. These amino acids (leucine, isoleucine, lysine, methionine, valine, threonine, phenylalanine, tryptophan) must therefore be introduced with the foods, in order to avoid specific nutritional deficiencies In the first two years of life, two other amino acids become essential, called respectively arginine and histidine.

": 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:

C.U.D. (digestive utilization coefficient): it 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;

FOR. (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;

N.P.U. (net protein utilization = net protein utilization): expresses the digestibility and biological value of the protein.

is inversely proportional to age:

2 g / kg / day in the newborn

1.5 g / kg / day at 5 years

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 PROTEIN: 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

DRY 36,9 GRAIN 33,9 BRESAOLA 32 PINE NUTS 31.9 ROASTED PEANUTS 29 RAW HAM 28 SALAMI 27 ... DRIED BEANS 23,6 CHICKEN BREAST 23,3 FRESH TUNA 21,5 ADULT CATTLE FILLET 20.5 COD OR HAT 17,0
Food Biological value EGG 100 MILK 91 BEEF 80 FISH 78 SOY PROTEIN 74 RICE 59 GRAIN 54 PEANUTS 43 DRIED BEANS 34 POTATO 34
N.B. cooking food considerably decreases the biological value of proteins

Supplement Biological value WHEY PROTEIN >100 EGG PROTEIN 100 MILK'S PROTEINS >90 CASEIN PROTEIN <80 SOY PROTEIN <75 WHEAT PROTEIN <55