Biological value of proteins: types, how the body gets proteins, necessary foods and nutritional rules

2024 Author: Isabella Gilson | [email protected]. Last modified: 2023-12-17 03:14

In the article we will consider the biological value of proteins.

Protein metabolism occupies an important place in the various transformations of substances that are characteristic of living organisms. A significant influence on it is the nature of nutrition, the amount of protein taken with food. And, of course, its quality composition.

With insufficient intake of protein substances with food, the breakdown of proteins in the tissues of the body exceeds the volume of production. The accepted norms for a person take into account various climatic conditions, profession, age and other factors.

The state of protein metabolism depends not only on the amount of protein taken, but also on its composition, which determines the nutritional and biological value of proteins.

Daily requirement

The daily requirement for a person is 100-120 g with an energy expenditure of 12,000 kJ. For people who are engaged in physical labor - 130-150 g, and for children - 55-72 g. Lack or absence of proteins in foodoften accompanied by weight loss, growth retardation, cause many pathological changes in the body. Particularly sensitive to protein deficiency are the endocrine and nervous systems, as well as the cerebral cortex.

Factors that determine value

The accepted proteins differ significantly in biological value and amino acid composition. This is determined by the following factors:

1. The degree of protein absorption, which depends on the efficiency of its breakdown under the influence of digestive tract enzymes. A number of proteins, despite their related amino acid composition to the proteins of the human body, are almost never used in the form of food protein. Because they are not hydrolyzed by the protein of the human digestive system.
2. The proximity of the amino acid content of the protein to such a composition of body proteins. The closer the amino acid composition of a food protein is to the composition of body proteins, the higher is its biological value. For a person, for example, proteins of milk, meat, eggs are more biologically valuable. Since their amino acid composition is close to the amino acid composition of human tissues and organs. However, this does not exclude the intake of vegetable proteins, which contain the required amount of amino acids in a different ratio. What else affects the biological value of proteins?
3. The content of essential amino acids. Science has proven that out of the 20 known amino acids present in the protein, only 10 are capable of being produced in the human body - they are non-essential amino acid compounds, while the rest (leucine, valine,arginine, isoleucine, methionine, tryptophan, lysine, phenylalanine, threonine, histidine) cannot be synthesized and are considered essential. The amino acids arginine and histidine are semi-essential, i.e. they can be synthesized, but in insufficient quantities.

Types of proteins

Proteins are classified into species according to their different characteristics. Proteins are distinguished by shape:

1. Fibrous, which have an atypical secondary structure and elongated polypeptide chains. They don't dissolve in water. Examples of such proteins are collagen, keratin and fibrin.
2. Globular, which are characterized by folding their chains into a compact or dense spherical shape, forming hydrophobic groups, which facilitates their dissolution in polar solvents, such as water. Examples of globular proteins are most antibodies, enzymes, transport proteins, and some hormones.
3. Mixed, which have fibrillar and spherical parts.

By chemical composition

By chemical composition, proteins are classified into the following varieties:

1. Holoproteins or simple proteins, upon hydrolysis of which only amino acids are produced. Examples of these substances are collagens (fibrous and spherical), insulin and albumins.

2. Heteroproteins or conjugated proteins that contain a prosthetic group or polypeptide chains. The non-amino acid portion is called the prosthetic group. These proteins are cytochrome and myoglobin. conjugatedproteins are classified according to the characteristics of their prosthetic group:

• lipoproteins: cholesterol, phospholipids and triglycerides;
• nucleoproteins: nucleic acid;
• metalloproteins: metals.

3. Chromoproteins are conjugated proteins with chromophore groups.

4. Phosphoproteins are proteins that are conjugated to a phosphate containing radical. And different from other than phospholipid and nucleic acid.

5. Glycoproteins - This group consists of carbohydrates.

How does the body get protein?

Sources of protein are animal and vegetable products, but vegetable, unlike animal proteins, only benefit a person. They do not overwhelm the body with cholesterol, fats and calories. With their help, you can get the optimal amount of essential amino acids. Nevertheless, animal fats are also necessary for a person, and the body cannot do without them.

In order to get the required amount of amino acids, people need to follow certain dietary rules, which involve eating a certain amount of specific foods during the day. You can not eat a large amount of animal protein, or an excessive amount of vegetable protein - nutrition should be balanced.

The biological value of vegetable proteins is very high.

Sources

The main sources are:

• Fresh parsley. It contains 3.7 g of protein per 100 g.
• Spinach - 3 g of protein and other usefulsubstances in 100 g.
• Asparagus. Contains protein 3.2 g per 100 product.
• Cauliflower - 2.3g protein per 100g

The main sources of protein of high biological value of animal origin are:

• Chicken - 20-28g protein per 100g
• Cottage cheese – 19.2g per 100g
• Beef fillet - 18.9g per 100g
• Eggs - 18g per 100g
• Salmon - 20g per 100g

Protein Nutrition Rules

The biological value of various proteins must be taken into account. If the energy balance is observed, the consumption of foods that contain carbohydrates and fats is minimal, since proteins are the main building blocks of cells. They are needed for the constant renewal and functioning of tissues and organs. The standard daily protein intake for a person is 80-100 g, but in stressful situations and with increased physical activity, this need increases significantly.

How scarce is dangerous

Strong protein nutrition is necessary because the deficiency:

• helps reduce resistance to infection by reducing the formation of antibodies in the body;
• exacerbates inflammation due to impaired production of lysozyme and interferon;
• impairs enzyme synthesis and nutrient absorption;
• impairs the absorption of vitamins, causing beriberi;
• causes hormonal imbalances.

The main products with high biological value of animal proteins are:

1. Meat products: beef or veal, poultry, lean pork, rabbit. Meat contains all the essential amino acids in optimal proportions and in large quantities.
2. Fish: flounder, carp, cod, salmon, tuna, fish caviar. In terms of biological value, fish protein is close to meat protein, it contains a lot of methionine, an essential amino acid.
3. Eggs.
4. Dairy.
5. Plant products. The main sources of protein in this case are legumes - peanuts, peas, beans, lentils. In cereals (rye, wheat, rice, oats), the protein content is several times less. Proteins of plant origin do not contain a complete set of amino acids. However, it can be obtained by eating herbal products in the right combination.

We looked at the biological value of proteins.