Proteins

Description

Proteins are the basis of many animal body structures (eg muscles, skin and hair). They also form the enzymes that control chemical reactions in the body. Each molecule is composed of amino acids, which are sometimes characterized by the inclusion of nitrogen and sulfur (these elements are responsible for the distinctive smell of burning protein, such as the keratin in hair).

The body requires amino acids to produce new proteins and to replace damaged ones. Since the body has no way of storing amino acids, they must be present in the diet. Protein mass is continuously renewed at a rate greater than 250 to 300 g per day for a total of about 11 kg per adult.

Excess amino acids are discarded, typically in the urine. For all animals, some amino acids are essential (an animal can not produce them internally) and some are non-essential (the animal can produce them from other nitrogen compounds). Twenty amino acids are found in the human body, and a dozen of them are essential and therefore must be included in the diet.

A diet that contains adequate amounts of amino acids (especially those that are essential) is particularly important in some situations: during the phases of development and maturation, pregnancy, lactation, or during an injury (a burn , for example).

Protein sources

All the amino acids are found in protein-containing foods, whether of animal or vegetable origin. However, they are not in optimal proportions necessary for metabolism, certain amino acids are present in a limited quantity. In this case the absorption of all the other amino acids is reduced proportionately to amount of the smallest quantity.

Animal proteins are complete, ie contain all the essential amino acids in sufficient quantity. But they are often associated with fat (cheese, meats).

Proteins of vegetable origin are incomplete. ie they lack one or more essential amino acids in adequate amounts. The use of plant products most often used as a protein source require culinary or technological processes to make them more digestible and destroy most of the antinutritional elements they may contain. In addition, these vegetable protein sources contain various compounds some of which may play a role in preventing certain nutritional illnesses (fiber, vitamins, trace elements, other factors of protection against oxidative stress).

It is possible to combine two incomplete protein sources to make it a complete protein source. Food combinations are based on different cultural culinary traditions, such as rice and beans or wheat and chickpeas.

Sources of dietary protein include meats, tofu and other soy products, eggs, legumes and dairy products such as milk and cheese.

See the list of foods that provide the most protein

Needs

Scientists at the CNERNA-CNRS advocate RDI (Recommended Dietary Intake), which are related to the weight of people, factored, depending on age, by coefficiants ranging from 0.8 (adult) to 2.6 (infants ).

Excess amino acids can be converted into glucose and used as a source of energy through a process called gluconeogenesis. The remaining amino acids are discarded after conversion.

Very high protein diets (up to 4 times the RDI, ie 400% in Nutritiomètre ®) have been recommended to ensure maximum muscle growth. These practices are not safe and should not be followed without close medical supervision.. They can induce an increase in urinary calcium and nitrogen loss.

(Source: "Recommended dietary allowances for the French population," the CNERNA-CNRS. Edition coordinated by Ambroise Martin.)

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