Balanced nutrition: the 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 concern for humanity. Perhaps the biggest misconception is the belief that the problem of proper human nutrition can be solved by creating a sufficient amount of necessary food products. Objective analysis shows that the free choice of such products in modern human society in most cases leads to nutritional disorders, which, depending on many genetic and phenotypic characteristics of a person, provoke the development of a number of serious diseases.

In the history of science, there are two main theories of nutrition. The first one arose in ancient times, the second one – classical, often called the theory of balanced nutrition – appeared more than two hundred years ago. The second theory, which is dominant at present, replaced the ancient one and is one of the remarkable achievements of experimental biology and medicine.

Syndromes associated predominantly with nutritional disorders (according to: Haenel, 1979, with additions)

Overnutrition
Carbohydrates, refined starches and sugars	Proteins
Diseases, disorders
Cardiovascular diseases (hypertension, atherosclerosis, varicose veins, thrombosis) Chronic bronchitis, pulmonary emphysema Gastrointestinal diseases (ulcers, gastritis, enteritis, ulcerative colitis, hemorrhoids) Appendicitis, cholecystitis, pyelonephritis caused by E. coli Cholecystitis Gallstone disease Kidney stone disease Diabetes Hyperlipidemia Toxicosis of pregnancy Epilepsy, depression Multiple sclerosis Periodontosis	Cardiovascular diseases (myocardial infarction, hypertension, atherosclerosis, thrombophlebitis, embolism, microangiopathy) Diabetes Hypercholesterolemia Toxicosis of pregnancy
Prevention
Reducing the consumption of easily digestible and refined carbohydrates	Reduce protein intake

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Ancient Theory of Nutrition

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

The main postulates of the theory of balanced nutrition

The theory of balanced nutrition emerged together with classical experimental natural science and, in essence, remains the dominant worldview today. The fundamentals of this theory are set out in a number of handbooks 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 Nutrition, 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 et al., 1984; Konyshev, 1985, 1990; Field, 1985; Heusner, 1985; Ugolev, 1985, 1987a; Emmanuel, Zaikov, 1986, and others. We will focus our attention on some issues that are less often in the spotlight, although they are extremely important for understanding the essence of classical theory.

The classical theory of nutrition is quite modern, that is, it meets the criteria of today and has played an exceptional role in the progress of a number of sciences and technologies. It first began to form when it became clear that the ancient schemes of blood circulation and digestion were incorrect and should be replaced: the first - by the doctrine of blood circulation, originally expressed by W. Harvey in 1628 and refuted the ideas that prevailed in the time of Galen, the second - by new ideas about digestion, developed by R. Reaumur and L. Spallanzani. The latter is especially important, since the idea of u200bu200bpreparing body fluids from food was replaced by a fundamentally new idea of u200bu200bdecomposing food into elements, some of which (the actual 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 views on the essence of nutrition and its disorders, as well as on industrial technologies, one way or another related to food products.

The theory of balanced nutrition in its modern form is not so much a theory as a paradigm, that is, a set of theories, methods, and ways of thinking. It is one of the most beautiful creations of the human mind, one of its 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 19th – early 20th century. This theory is associated with ideas about ideal food and optimal balanced nutrition, which were based on balanced approaches to the assessment and diet, which retain their significance today.

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

1. nutrition maintains the molecular composition of the body and compensates for its energy and plastic expenditure;
2. The ideal diet is one in which the intake of nutrients corresponds as closely as possible (in terms of time and composition) to their consumption;
3. the entry of nutrients into the blood is ensured 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 significance – 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;
6. food is utilized 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 of conservation of constancy of the molecular composition of the organism and nutrition

In his work devoted to the main results of the development of biological sciences in the 19th century, I. M. 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. In relation to living organisms, one could also speak of the law of conservation of their molecular composition.

The balanced approach is that the nutrients entering the body must compensate for their losses associated with the 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 such a set of substances that compensates for the substances spent on building body structures and work. Consequently, the balanced approach is associated with maintaining the constancy of the molecular composition of living systems.

Protein and amino acid requirements according to age (according to: FAO/WHO.., 1973)

Food component	Amount of substance consumed at age
	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	30	10
Leucine	161	45	14
Lysine	103	60	12
Methionine + cystine	5	27	113
Phenylalanine + tyrosine	125	27	14
Threonine	87	35	7
Tryptophan	17	4	4
Valin	93	33	10
Total amino acid requirements	714	261	84
Ratio of total amino acid requirement to protein requirement	0.39	0.33	0.15

Food

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

1. actual food substances – proteins, carbohydrates, fats, vitamins, etc.
2. ballast substances;
3. harmful (toxic) compounds.

If the valuable part of food is the nutrients needed for metabolism, then food can be purified from ballast according to classical theory.

The classical theory of balanced nutrition, at least at a sufficiently high level of development, made it possible to answer the questions of what the ideal food and the minimally adequate diet should be, what food defects and to what extent would affect the functions of the organism or could prove incompatible with life. Indeed, defective food, consisting of a set of substances lacking certain necessary components, could cause illnesses and even death in experimental animals. On the other hand, an artificial diet, characterized as complete in the light of the theory of balanced nutrition, could indefinitely support the life of not only a given individual, but also the offspring it reproduces. However, as will be shown below, such an approach to the composition of food contained errors that seem obvious to an objective observer if he switches to the positions of the new theory of adequate nutrition.

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The main consequences of the theory of balanced nutrition

The theory of balanced nutrition is remarkable not only for its logical coherence and clarity and experimental validity, but also for its ability to predict unknown phenomena that were later discovered, or patterns that can be and were actually discovered under certain experimental conditions. Knowing the set of necessary nutrients, it is possible to design food rations sufficient for the survival, normal functioning and development of organisms. If any disturbances occur, as the theory of balanced nutrition postulates, the defect should be attributed to the deficiency of one or more necessary nutritional factors. It was in this way that vitamins, microelements, essential amino acids, etc., necessary for the body were discovered one after another. In particular, it was demonstrated that approximately half of the 20 amino acids that make up proteins are essential for the implementation of certain metabolic functions. The number of essential amino acids varies from 10 to 13 depending on the animal species, its diet, etc. Thus, humans have 10 essential amino acids, rats and chickens have 13, and the average animal has 12. However, organisms of all species have 8–9 common essential amino acids. Interestingly, in chickens at least three essential amino acids (tyrosine, cystine, and hydroxylysine) out of 13 can be synthesized only with a limited supply of food substrates (review: Parks, 1982).

The achievements listed above were truly remarkable consequences of the consistent application of the theory of balanced nutrition. According to this theory, not all components of food are necessary to maintain the body's vital functions, but only the useful ones. By concentrating them, one can obtain so-called enriched food products.

Based on this idea, it was possible to increase the proportion of nutrients in food and improve the ratio between them, bringing it closer to the ideal. (By the ideal ratio of nutrients, most researchers understood such a ratio of incoming food substances that would best meet the energy and plastic needs of the body.)