Since ancient times, people have understood the great importance of healthy food. The thinkers of antiquity, Hippocrates,
Celsus, Galen and others devoted entire treatises medicinal properties of various types of food and reasonable consumption. An outstanding scholar of the East Abu Ali Ibn Sina (Avicenna) considered food a source of health, strength and vitality.
I. Mechnikov believed that people age and die prematurely due to unhealthy diet and that a person who feeds rationally can live 120 — 150 for years.
Nutrition provides the most important function of the human body, supplying it with the energy necessary to cover the costs of life processes. The renewal of cells and tissues also occurs due to the ingestion of “plastic” substances into the body with food - proteins, fats, carbohydrates, vitamins and mineral salts. Finally, food is the source of the formation of enzymes, hormones and other metabolic regulators in the body.
To maintain the normal flow of energy, plastic and catalytic processes, the body requires a certain amount of various nutrients. Metabolism in the body, the structure and functions of cells, tissues and organs depend on the nature of nutrition.
Proper nutrition, taking into account the conditions of life, work and life, ensures the constancy of the internal environment of the human body, the activity of various organs and systems and, thus, is an indispensable condition for good health, harmonious development, high efficiency.
Improper diet significantly reduces the body's defenses and performance, disrupts metabolic processes, leads to premature aging and can contribute to the emergence of many diseases, including those of infectious origin, as a weakened body is subject to any negative impact. For example, excessive food, especially when combined with neuropsychiatric tension, an inactive lifestyle, drinking alcohol and smoking, can lead to many diseases.
Atherosclerosis, obesity, gallstone disease, gout, diabetes mellitus and polyosteoarthrosis are classified by the World Health Organization (WHO) among the diseases associated with overnutrition. Overeating is often the cause of diseases of the circulatory system.
Malnutrition and hunger cause malnutrition, especially among the populations of developing and dependent countries.
According to WHO, at present, the required amount of food is provided to less than a third of the world's population.
Constant malnutrition gives rise to kwashiorkor, a serious illness of children due to protein deficiency of food, which is widespread in countries that were until recently in colonial dependence. In this disease in children, growth and mental development are slowed down, bone formation is disturbed, and changes in the liver and pancreas occur.
The problem of nutrition of the population is solved in terms of providing the products with the necessary energy value (caloric content). The implementation of the Food Program provides for a significant improvement in the structure of the nutrition of the Soviet people by increasing the production of meat, dairy products, vegetables and fruits.
It is planned to expand the range of food products, to improve their quality.
The growth of material well-being allows you to organize on the basis of scientific rational nutrition of the entire population of our country.
A rational diet is considered to be one that ensures the normal functioning of the body, a high level of efficiency and resistance to adverse environmental factors, and a maximum duration of active life.
The biological value of food is determined by the content of essential nutrients the body needs - from proteins, fats, carbohydrates, vitamins, mineral salts. For normal human life, it is necessary not only to supply it with adequate (according to the body's needs) amount of energy and nutrients, but also to observe certain relationships between numerous nutritional factors, each of which has a specific role in metabolism. Nutrition, characterized by an optimal ratio of nutrients, called balanced.
Sources of nutrients are foods of animal and vegetable origin, which are conventionally divided into several main groups. The first group includes milk and dairy products (cottage cheese, cheeses, kefir, yogurt, acidophilus, cream, etc.); the second is meat, poultry, fish, eggs, and products made from them; the third - bakery, pasta and confectionery, cereals, sugar, potatoes; fourth, fats; fifth — vegetables, fruits, berries, greens; sixth - spices, tea, coffee and cocoa.
In nature, there is no ideal food that would contain a complex of all nutrients needed by man (with the exception of mother's milk). With a varied diet, that is, a mixed diet consisting of products of animal and vegetable origin, quite a lot of nutrients are usually supplied to the human body.substances. A variety of foods in the diet has a positive effect on its nutritional value, as different products complement each other missing components. In addition, a varied diet promotes better digestion.
Food as a source of energy
Throughout his life, a person performs a variety of physical movements associated with the movement of the body and the implementation of work. The heart, muscles, digestive and other systems work all my life in the body, some substances disintegrate and others are synthesized, which is the basis of metabolism and constant cell renewal. These processes require energy, which the body receives from nutrients.
Food substances in the human body undergo changes as a result of oxidation by oxygen of the air, which enter through the respiratory organs and are carried to all cells. This releases a certain amount of energy in the form of heat. It should be noted that in the first phase of metabolism, food substances are transformed under the influence of enzymes into simpler ones: proteins - into amino acids, complex carbohydrates - into simple ones, fats - into glycerin and fatty acids. In this phase, as a result of the decomposition of food substances, energy is not only not released, but also consumed, as evidenced by the so-called specific dynamic effect of food. In the second phase, the decomposition products of food substances undergo further decomposition and are oxidized to carbon dioxide and water with the release of energy.
When 1 g of proteins and 1 g of carbohydrates are completely decomposed in the body, 4 kcal (16,747 kJ) of energy, 1 g of fat - 9 kcal (37,681 kJ), ethyl alcohol - 7 kcal (29,309 kJ), organic acids (citric, apple, acetic, etc.) - by 2,5—
kcal (10,4670 — 15,0724 kJ). Other nutrients are not sources of energy. Thus, if you know exactly how much of the energetic substance goes into the human body with food (this is determined by special tables), you can easily calculate the daily amount of energy received.
Food is not equivalent in energy value; it depends on their chemical composition. The main energy material are carbohydrates, fats and, in part, proteins. It does not follow from this that food substances can be replaced by each other and it does not matter for the organism, due to what products energy is obtained. The value of various foods is determined not only by their energy value, but also by their qualitative composition. So, simple carbohydrates (sugar and other sweets) do not contain any biologically valuable substances, except energy, therefore the energy of these products is called “empty calories”. When oxidized in the human body ethyl alcohol coming from alcoholic beverages produces toxic substances that are harmful to health.
Depending on the amount of energy, all food products are divided into products with high, medium and low energy value. The products with high energy value include butter and vegetable oils, animal fats, fatty pork, sugar, honey, confectionery. Moderate fat content of sausage, meat and fish, sour cream, cream, cheese, bakery and pasta, cereals have an average energy value. Low energy value is characterized by vegetables and fruits, berries, milk, kefir, lean meats, fish, lean curd, eggs.
The nutrients in excess in the body are converted into fat and deposited in adipose tissue, which under certain conditions can lead to the development of obesity. Therefore, it is necessary to build a diet so that the amount of incoming nutrients corresponds to the body's energy expenditure for basal metabolism, physical activity, eating, digestion and assimilation of food. The main metabolism is carried out in the process of vital activity of the body in a state of complete rest. In case of diseases accompanied by fever, it rises (with thyrotoxicosis, tuberculosis, pulmonary and heart failure).
The specific dynamic effect of food is associated with its digestion and assimilation. Thus, the intake of protein foods contributes to an increase in the level of the basic metabolism on average by 30%, fatty - by 4 — 14%, carbohydrate — by 4 — 7%. On average, the main metabolism under the influence of food increases by 10 — 15%, which is about 850 kJ per day. This property of the body to spend a lot of energy on the specific dynamic effect of protein foods is used to treat obesity.
The correspondence of the energetic substances entering the body to the energy expenditure on its vital activity is ensured by a balanced diet. A reliable indicator of compliance with energy intake and consumption in the body of an adult is the constancy of body weight. Excess energy value of the diet leads to an increase in body weight. With a lack of food, the body spends spare energy substances, as a result of which a person loses weight. With a prolonged shortage of nutrients, not only spare substances are consumed, but also cell proteins, which significantly reduces the protective properties of the body and adversely affects the state of health.
The need for human energy
In 1982, the Ministry of Health approved new standards for the physiological needs of the body for energy and nutrients for various groups of people, developed by the Institute of Nutrition of the Academy of Medical Sciences. In determining the energy needs of adults, the age, gender and nature of work were taken into account. According to these norms, the adult working-age population at the age of 18 — 60 years is subdivided into 5 groups depending on energy consumption.
The first group includes mainly persons of mental labor - heads of enterprises and organizations; engineering and technical personnel, whose work does not require substantial physical activity; medical workers, except surgeons, nurses and nurses; teachers, educators, except sports; literary workers and journalists; employees of cultural and educational institutions, planning and accounting; secretaries, clerks; Persons whose work is associated with a great deal of nervous and insignificant physical tension (employees of control panels, dispatchers, etc.).
The second group includes workers engaged in light physical labor - engineering and technical personnel, whose work requires some physical effort; persons employed in automated processes; radio electronic industry workers; sewers; agronomists; livestock specialists, veterinary workers; nurses and nurses; sellers of department stores, service workers; watch industry workers; communication and telegraph workers; teachers, instructors of physical culture and sports, trainers.
The third group includes persons performing physical work of moderate severity: machinists (employed in metalworking and woodworking), mechanics, fitters, tuners; surgeons; chemists; textile workers, shoemakers; drivers of various types of transport; food industry workers; workers of public utilities and catering; food sellers; foremen of tractor and field brigades; railway workers; water springs; workers of auto and electric vehicles; machinists lifting mechanisms; printers.
The fourth group brings together people of heavy physical labor - construction workers; the vast majority of agricultural workers and machine operators; miners engaged in surface work; oil and gas industry workers; metallurgists and foundrymen, except for persons assigned to the fifth group; workers in the pulp-and-paper and woodworking industry (slingers, scaffold workers, woodworkers, carpenters, etc.), workers in the construction materials industry, except for those in the fifth group.
The fifth group includes workers who perform particularly hard physical labor - miners working on underground works; steelworkers; loggers and wood workers; bricklayers; concrete workers; excavators; loaders whose labor is not mechanized; workers engaged in the production of building materials whose labor is not mechanized.
The energy requirement of the adult working-age population in our country is determined for three age groups: 18 — 29, 30 — 39, and 40 — 59 years. Due to the lower body mass and less intensive metabolic processes in women, the need for a woman’s body for energy is on average 15% lower than that of men.
When determining the needs of the adult working-age population at the age of 18 — 60 years in energy, the mass 70 kg for men and 60 kg for women was taken as the average ideal body weight. The recommended average daily energy requirements of the adult working-age population of our country, depending on the group of labor intensity, are presented in Table. 1.
Table 1. The daily energy requirement (kJ) of the adult working-age population (data in kcal are given in brackets)
|Group work intensity||Age,||Men||Women|
|1-I group||18-29||11 723 (2800)||10 048 (2400)|
|30-39||11 304 (2700)||9630 (2300)|
|40-59||10 676 (2550)||9211 (2200)|
|2-I group||18-29||12 560 (3000)||1.0 676 (2550)|
|30-39||12 142 (2900)||10 258 (2450)|
|40-59||11 514 (2750)||9839 (2350)|
|3-I group||18-29||13 398 (3200)||11 304 (2700)|
|30-39||12 979 (3100)||10 886 (2600)|
|40-59||12 351 (2950)||10 467 (2500)|
|4-I group||18-29||15 491 (3700)||13 188 (3150)|
|30-39||15 072 (3600)||12 770 (3050)|
|40-59||14 444 (3450)||12 142 (2900)|
|5-I group||18-29||18 003 (4300)|
|30-39||17 166 (4100)||—|
|40-59||16 329 (3900)||—|
Notes. 1. Women are forbidden to engage in the Soviet Union especially in heavy physical labor. 2. 1 4,1868 kcal equal (rounded 4,187) kJ.
The energy requirement of men at the age of 60 — 74 retired years, on average does not exceed 9630 kJ (2300 kcal) per day, at the age of 75 years and older — 8374 kJ (2000 kcal). The energy needs of women are 8792 (2100 kcal) and 7955 (1900 kcal), respectively.
The energy needs of people living in the Far North are, on average, 10 — 15% higher and those living in the southern regions of the country are 5% lower than those living in the temperate zone.
Plastic function of nutrients
Food substances (proteins, fats, carbohydrates, vitamins, minerals) are an important source of material for building cells and tissues, enzymes, hormones and other vital substances; They are used as biocatalysts. In the human body, the processes of renewal of various elements of cells and tissues continuously occur. Some cells die, and others appear instead. All this requires a constant influx of nutrients into the body.
The main plastic material for living organisms are proteins. The exchange of proteins as a central link in biochemical processes is the basis of life. Proteins make up approximately 15 — 20% of the wet mass of various tissues of the human body, and lipids (fats) and carbohydrates — all of 1 — 5%. Biological membranes, which play an important role in the function of cells, are built from proteins and lipids. Muscle tissue, heart, liver, brain, and even bones contain significant amounts of protein.
The only source of proteins and essential amino acids for humans is food: in almost all products, with the exception of sugar and vegetable oils, various proteins are present. Due to moderate heating and boiling, the nutritional value of protein foods increases, they are better absorbed.
Proteins form the basis of most enzymes. Other substances, such as vitamins, are also involved in the construction of complex enzymes. Enzymes perform the main functions of metabolism, the construction of human-specific cellular structures. With the help of enzymes in the body, energy substances are synthesized, which are destroyed with the release of the required body energy.
An important function of proteins is to provide barrier properties, the tissue specificity of the organism, its immunity.
In complex compounds with lipids, carbohydrates, vitamins, mineral salts, metals, pigments, drugs and even oxygen, proteins perform the function of transport of these substances to various organs and tissues. They help to maintain a certain amount of water in the cells and in the intercellular space.
Fats and fat-like substances (lipids) are the structural elements of a living cell and provide the physiological functions of the body.
The fatty layer around the internal organs of the abdominal cavity protects them from mechanical damage. In the subcutaneous tissue, fat as a poor conductor of heat limits heat transfer and protects the body from hypothermia.
Mineral substances are involved in metabolic processes of cells of various tissues. Of particular importance are minerals in the construction of bone tissue, density and resistanceIts physical activity depends on the content of calcium and phosphorus. Without mineral substances in the body many enzymatic processes could not be carried out. Minerals affect blood formation, maintain osmotic pressure in cells and extracellular fluid, participate in the transfer of oxygen to the tissues, are part of many hormones and other biologically active compounds.
Water and the products of its dissociation are components of the living cell. Only in the aquatic environment can many biochemical reactions occur. An adult body weight 65 kg contains about 40 liters of water, of which 25 liters are inside cells and 15 liters are in extracellular fluid. The exchange of childbirth in the body is very intense. About 2,5 l of water is excreted daily from urine, feces and exhaled air. Sweating regulates the constancy of body temperature. With increasing ambient temperature or intense physical work, perspiration dramatically increases. In some cases, the amount of sweat excreted by a person per day can reach 10 l. That is why regular consumption of water is an important factor in maintaining the constancy of the internal environment of the body, as well as the structure and function of all cells and tissues.
Thus, all food substances entering the body play a certain plastic role in the structure of tissues, cells, intracellular formations and biologically active substances that perform various physiological functions.