Balanced nutrition: classical theory

There is no need to prove that nutrition is one of the central problems, the solution of which is the subject of constant worries of mankind. It is hardly the biggest misconception - the belief that the problem of proper human nutrition can be solved by creating a sufficient number of necessary food products. An objective analysis shows that the free choice of such products in modern human society in most cases leads to eating disorders, which, depending on many of the genetic and phenotypic characteristics of a person, trigger the development of a number of serious diseases.

In the history of science two basic theories of nutrition are known. The first arose in the days of antiquity, the second - the classical, often called the theory of balanced nutrition - appeared more than two hundred years ago. The second theory, which currently dominates, has replaced the ancient one and is one of the remarkable achievements of experimental biology and medicine.

Syndromes associated mainly with eating disorders (according to: Haenel, 1979, with additions)

Excessive food
Carbohydrates, refined starch and sugars	Proteins
Diseases, disorders
Diseases of the cardiovascular system (hypertension, atherosclerosis, varicose veins, thrombosis) Chronic bronchitis, emphysema Diseases of the gastrointestinal tract (ulcers, gastritis, enteritis, ulcerative colitis, hemorrhoids) Appendicitis, cholecystitis, pyelonephritis caused by E. Coli Cholecystitis Cholelithiasis Renal stone disease Diabetes Hyperlipidemia Toxicosis of pregnancy Epilepsy, depression Multiple sclerosis Periodontal disease	Diseases of the cardiovascular system (myocardial infarction, hypertension, atherosclerosis, thrombophlebitis, embolism, microangiopathy) Diabetes Hypercholesterolemia Toxicosis of pregnancy
Prevention
Decreased intake of easily assimilated and refined carbohydrates	Decreased protein intake

[1], [2], [3], [4], [5], [6], [7], [8]

The ancient theory of nutrition

Ancient theory is associated with the names of Aristotle and Galen. According to this theory, the food of the body is due to blood, which is continuously formed from nutrients as a result of a complex process of an unknown nature, similar to fermentation. In the liver, the blood is purified and then used to feed the organs and tissues. Thus, using modern terminology, preliminary digestion was considered as a process of transformation of nutrients into other substances that serve as a source of energy and building components.

The basic postulates of the theory of balanced nutrition

The theory of balanced nutrition arose together with classical experimental natural science and, in essence, remains the dominant world view even now. The foundations of this theory are set forth in a number of manuals on various fields of biology and medicine. Various aspects of the theory of balanced nutrition are considered, in particular, in the following reports: Sherman, 1937; Winitz et al., 1970; Therapeutic nourishment, 1971; Chemical and physiological problems ..., 1972, 1975, 1976; Pokrovsky, 1974, 1979; Haenel, 1979; Samsonov, Meshcheryakova, 1979; Harrison et al., 1979; Protein metabolism ..., 1980; Parks, 1982; Petrovsky, 1982; Le Magnen, 1983; Kanevsky and others, 1984; Konyshev, 1985, 1990; Field, 1985; Heusner, 1985; Ugolev, 1985, 1987a; Emmanuel, Zaikov, 1986, etc. We will focus our attention on some issues that are less likely to fall in the field of view, although they are extremely important for understanding the essence of the classical theory.

The classical theory of nutrition is quite modern, that is, meets the criteria of today and played an exceptional role in the progress of a number of sciences and technologies. For the first time it began to form when it became clear that the ancient schemes of blood circulation and digestion are wrong and should be replaced: the first - the blood circulation doctrine, originally expressed by W. Harvey in 1628 and refuted the ideas dominating in the time of Galen, the second - new concepts on digestion, developed by R. Reaumur and L. Spallanzani. The latter is especially important, since the idea of preparing body fluids from food was replaced by a fundamentally new idea of decomposition of food into elements, some of which (actually food substances-nutrients) were assimilated, that is, included in the body, and the other part (ballast substances) was discarded. Without exaggeration, we can say that this idea was a turning point in the views on the nature of nutrition and its violation, as well as on industrial technologies, one way or another concerning food.

The theory of balanced nutrition in the modern form is not a theory, but a paradigm, that is, a set of theories, techniques and ways of thinking. She is one of the most beautiful creations of the human mind, one of his greatest achievements in practical and humanistic consequences.

The classical theory of balanced nutrition, based on the works of R. Reaumur, L. Spallanzani, A. Lavoisier, G. Helmholtz and others, was finally formed in the late XIX - early XX century. With this theory, the concepts of ideal food and optimal balanced nutrition are associated, based on balanced approaches to evaluation and dietary regimen, which still retain their importance.

The classical theory of balanced nutrition can be reduced to several fundamental postulates:

1. nutrition supports the molecular composition of the body and reimburses its energy and plastic costs;
2. ideal food is the food, in which the intake of nutrients as accurately as possible (by time and composition) corresponds to their expenditure;
3. the supply of nutrients to the blood is provided by the destruction of food structures and the absorption of nutrients necessary for metabolism, energy and plastic needs of the body;
4. food consists of several components, different in physiological meaning - nutrients, ballast substances (from which it can be purified) and harmful (toxic) substances;
5. the value of a food product is determined by the content and ratio of amino acids, monosaccharides, fatty acids, vitamins and some salts in it;
6. the utilization of food is carried out by the body itself.

Let us consider some of these postulates, as well as a number of consequences arising from the theory of balanced nutrition, in more detail.

Laws to preserve the constancy of the body's molecular composition and nutrition

In his work on the main results of the development of biological sciences in the XIX century, IM Sechenov wrote that the classical theory of nutrition is based on the basic laws of conservation of matter and energy in relation to biological systems. With respect to living organisms, one could also speak about the law of conservation of their molecular composition.

The balanced approach boils down to the fact that food substances entering the body must compensate for their losses associated with basic metabolism, external work, and for young organisms - also with growth. In other words, the theory of balanced nutrition is based on the fact that the body must receive a set of substances that reimburse substances used to build body structures and work. Consequently, a balanced approach is associated with maintaining the constancy of the molecular composition of living systems.

Requirements for protein and amino acids depending on age (by: FAO / WHO .., 1973)

Food component	The amount of consumed substance at the age of
	3-6 months.	10-12 months	Adults
Protein (g / kg body weight)	1.85	0.80	0.57
Amino acids (mg / kg body weight):
Isoleucine	70	Thirty	10
Leucine	161	45	14
Lysine	103	60	12
Methionine + cystine	5	27th	113
Phenylalanine + tyrosine	125	27th	14
Threonine	87	35	7th
Tryptophan	17th	4	4
Valine	93	33	10
Total demand for amino acids	714	261	84
The ratio of the total demand for amino acids to the protein requirement	0.39	0.33	0,15

Food

For the theory of balanced nutrition, it is important that food consists of several basic components, different in their biological significance:

1. the actual nutrients - proteins, carbohydrates, fats, vitamins, etc.
2. ballast substances;
3. harmful (toxic) compounds.

If the valuable part of the food is the nutrients necessary for metabolism, then the food in accordance with the classical theory can be purified from the ballast.

The classical theory of balanced nutrition, at least at a sufficiently high level of development, allowed to answer questions about what should be an ideal food and a minimum sufficient diet, what food defects and to what extent will be reflected in the functions of the organism or may be incompatible with life. Indeed, a defective food consisting of a set of substances lacking certain necessary components could cause diseases and even the death of experimental animals. On the other hand, an artificial diet, characterized as fully-fledged in the light of the theory of balanced nutrition, could indefinitely sustain the life of not only this individual, but also of the reproductive progeny. However, as will be shown later, this approach to the composition of food contained errors that seem obvious to the objective observer if he moves to the position of a new theory of adequate nutrition.

[9], [10], [11]

The main consequences of the theory of balanced nutrition

The theory of balanced nutrition is remarkable not only for harmony and clarity of logic and experimental validity, but also for the ability to predict unknown phenomena that were then discovered, or patterns that can be detected and indeed discovered under certain experimental conditions. Knowing the set of necessary nutrients, it is possible to design food rations sufficient for survival, normal functioning and development of organisms. If there are any disturbances, as the theory of balanced nutrition postulates, the defect should be attributed to the shortage of one or several necessary nutritional factors. In this way, vitamins, trace elements, essential amino acids, etc., were discovered one by one, one after another. In particular, it was demonstrated that about half of the 20 amino acids making up proteins are indispensable for the realization of certain metabolic functions. The number of essential amino acids varies from 10 to 13 depending on the type of animal, its diet, etc. Thus, in humans there are 10 essential amino acids, in rats and chicks - 13, in the average animal - 12. However, in organisms of all kinds there is an 8- 9 common essential amino acids. Interestingly, in chicks, at least three essential amino acids (tyrosine, cystine and hydroxylizine) of 13 can be synthesized only with limited intake of food substrates (review: Parks, 1982).

The above achievements were a truly remarkable consequence of the consistent application of the theory of balanced nutrition. According to this theory, to maintain the vital activity of the body, not all the components of food are needed, but only useful ones. Concentrating them, you can get so-called enriched foods.

On the basis of this idea, it was possible to increase the share of nutrients in food and improve the ratio between them, bringing it closer to the ideal. (Under the ideal ratio of nutrients, most researchers understood the ratio of incoming nutrients that would best meet the energy and plastic needs of the body.)