Scientific Theories of Nutrition

These include the following:

· Classical theory of balanced nutrition by academician A. A. Pokrovsky (60s of ХХ century).

· Theory of adequate nutrition by аcademician A. M. Ugolev (1975) — in addition to the theory of rational nutrition the membraneous and endocellular digestion is taken into account.

· Functional-homeostatic theory of nutrition by V. V. Vanchanen (1995) also takes into account functions and biological effects of different nutrients.

Nonconventional (Unscientific) Concepts of Nutrition

These contain both rational moments and antiscientific statements. They include:

· Vegetarianism (veganstvo)

· Nutrition of macrobiotics (Japan)

· The concept of “yan” and “in” (China)

· Nutrition in yogi system

· Separate nutrition by G. Shelton

· Nutrition of the ancestors (raw food, dry food)

· Reduced nutrition (theory of “alive energy” in vegetable food)

· Concept of coefficients of alimentary value by E. Carise (“point diet”) (Germany)

· Complete long-lived or temporary starvation

· Absolutization of nutrition optimality (Selective diet for each separate person — USA)

 

Recommendations for Practical Classes on the Theme

Key Questions

· Types of nutrition (rational, preventive, clinical, clinical-preventive), their differentiation and purposes.

· The basic principles of a balanced diet.

· Theories of nutrition. Functions of food. Concept of dietary and food status of the man, methods of its study.

· Methods of controlling the observance of balanced diet principles in a separate man and in collectives of people.

· Methods of assessment of a daily energy consumption of a human organism and food value of foodstuffs.

· Bases of nutrition at unfavourable ecological conditions.

· Norms of nutrition, parameters which are taken into account at their elaboration.

· Classification of alimentary and alimentary-conditioned diseases, examples, causes, manifestations, treatment and prevention.

Self Test

1. What methods are used to determine the caloricity of man’s nutrition?

A. direct and indirect calorimetry

* B. a laboratory and calculation method

C. a tabular-chronometric method

D. a spectrophotometric method

2. The optimal number of meals for an adult man is

A. 2-3 times a day

* B. 4-5 times a day

C. 5-6 times a day

D. when the feeling of hunger occurs

E. every 2-3 hours

3. A clinical nutrition is developed for:

A. diseases caused by ecological conditions

* B. for feeding patients in medical establishments

C. diseases which badly yield to treatment

D. persons contacting with occupational hazards

4. On medical examination of male drivers in 10 % of persons an increased body weight (65 % higher than normally) was revealed. What is their nutritional state?

A. Normal status (adequate nutrition)

B. Obesity of 1st degree

C. Obesity of 2nd degree

* D. Obesity of 3rd degree

E. Obesity of 4th degree

5. Determine the caloricity of a student’s diet, which basic exchange makes up 900 Kcal, and energy losses in all kinds of activity during a day make up 2,100 Kcal.

A. Caloricity of a daily diet is 900 Kcal.

B. Caloricity of a daily diet is 2,100 Kcal

* C. Caloricity of a daily diet is 3,090 Kcal

D. Caloricity of a daily diet is 90 Kcal

E. Caloricity of a daily diet is 1,545 Kcal

Problem Solving

1. The diet of a miner includes 90 grams of proteins, 65 grams of fats and 650 grams of carbohydrates. Dietary habits are chaotic. An interval between meals is very large. What group of work intensity does the miner refer to? What is the amount of his energy losses? What is the caloricity of the submitted diet? Will it cover energy losses of the miner? Estimate this diet.

2. A 39-year-old surgeon spends 3,100 Kcal daily. The diet of the surgeon contains 93 g of proteins (including 40 g of animal origin), 116 g of fats and 300 g of carbohydrates. Caloricity of the diet is 2,651 Kcal. He usually has three meals every day: breakfast — at 7.30, dinner — at 15.00, supper — at 20.00. The distribution of caloricity by meals is as follows: breakfast — 20 %, dinner — 50 %, supper — 30 %. Determine the group of work intensity, estimate caloricity of nutrition and diet regimen. Give recommendations for balanced nutrition.

3. Patient Н. aged 63 suffers from excessive body mass, there are expressed signs of coronary atherosclerosis, hypertension. He has meals 3 times a day, avoiding fatty and spicy food. Estimate his nutritional state. What recommendations for correction of nutrition of antisclerotic orientation should be given in this case?

4. A patient aged 53 has a body weight of 82 kg at a height of 162 cm. She has 3 meals a day; the diet is usual. On examination an increased sugar level in blood (during last 5 years) has been revealed. In anamnesis: her mother was ill with diabetes mellitus. Estimate the nutritional state. Give recommendations for preventive nutrition.

5. Estimate the nutrition rationality of citizen N., aged 65, having 3 meals a day (at 8 a.m., at 4 and 8 p.m.), consuming 100 g of proteins, 100 g of fats and 500 g of carbohydrates. A daily energy allowance is 2,700 Kcal.

Standard Answers

1. The miner belongs to the 4th group of work intensity. Depending on age, the amount of his daily energy losses makes up 3,900-4,300 Kcal. The caloricity of his diet is = 90 х 4.1 + 65 х 9.3 + 650 х 4.1 = 3,638 Kcal. The diet of the miner by caloricity does not correspond to his energy losses. The regularity of meals is disturbed. The time and frequency of meals should be regulated.

2. By energy losses the doctor-surgeon relates to the 3rd group of work intensity. Caloricity of his diet does not correspond to energy losses. A qualitative structure of the diet has deviations. The total amount of proteins (93g) in the diet corresponds to physiological norms, but the content of animal proteins is below the recommended norms — 43 % (instead of 55-60 %), total amount of fats in the diet is sufficient (116 g). The amount of carbohydrates in the diet is much lower than the norm. Instead of 426 g it makes up 300 g. The ratio of proteins, fats and carbohydrates in the diet is not rational: it is 1:1.2:3.2, while normally it is 1: 1:4-5. An interval between meals is more than 7 hours. The conclusion: the nutrition of the doctor-surgeon is not rational and imbalanced.

3. The nutritional status is excessive. Alimentary obesity, the development of ischemic cardiac disease in connection with hypercholesterolemia are probable. A fractional nutrition (6-8 times a day) with a ratio of P:F:C = 1:0.8:3, limitation of fats and unprotected carbohydrates to limit the caloricity of food up to 2,000-2,400 Кcal a day are necessary. The inclusion in a diet of alimentary antisclerotic factors is necessary, e.g. irreplaceable aminoacid methyonin (cheese, cottage cheese), PNFA (vegetable oil, fat of sea fish), phosphatides (vegetable oil, etc.), antioxidant vitamins C, A and Е.

4. The nutritional status is excessive. Alimentary obesity is quite probable. The exclusion of unprotected carbohydrates from a diet, fractional nutrition (6-8 times a day) with a ratio of P:F:C = 1:0.8:3, limited amount of fats are necessary. Daily caloricity of food should be 2,200 Кcal. It is necessary to include sugar substitutes (sorbite, xylite, fructose, etc.) in meals, to provide optimal supply of diet with vitamins.

5. We begin solving the problem with estimation of caloric content of nutrition with the help of calorimetric factors (At burning 1g of proteins and carbohydrates gives 4.1 Kcal, and 1g of fats –9.3 Kcal of heat):

100 x 4.1 + 100 x 9.3 + 500 x 4.1 = 3,390 Kcal,

This exceeds a daily energy allowance (2,700 Kcal). Besides a nonoptimal balance of proteins, fats and carbohydrates (1:1:5) is observed, which for elderly people should make up 1:0.8:3.

The regimen of nutrition is also irrational: three meals a day (it should be four meals a day), there are nonoptimal intervals between taking meals (between breakfast and dinner — 8 hours, between dinner and supper — 4 hours), These time intervals should make up 4 -5 hours.

The conclusion: the nutrition does not meet the demands of a balanced diet. It is nec­essary to decrease the consumption of fats by 20 g, carbohydrates — by 200g, to have 4 meals a day with intervals of 4-5 hours.

 

 

Theme No 5.

Value of Various Nutrients in Nutrition.

Functions of Proteins, Fats and Carbohydrates in the Body

A section of hygiene of nutrition devoted to studying the functions of food substances (nutrients) in organism is called nutriology.

Structure of Foods

v Nutrients — proteins, fats, carbohydrates, vitamins, mineral substances.

v Non-alimentary substances are substances adding organoleptic properties, i.e. color, smell, etc. to foods.

v Antialimentary substances — antitrypsins (in raw egg protein), antivitamins (ascorbinase, thiaminase), antimineral substances (phytates, oxalates).

v Toxic substances:

Ø inherent in foods — toxins of poisonous mushrooms, solanine in potato, etc.

Ø casually obtained pollutants of the environment — pesticides, heavy metals, dioxines, etc.

Table 17

Functions of Nutrients

Function	Nutrients
Energy	carbohydrates, fats, proteins, organic acids, etc.
Plastic	proteins, minerals, fats, carbohydrates
Bioregulatory	proteins, vitamins, mineral substances
Adaptive-regulatory	proteins, water
Immunoregulatory	proteins, vitamins, etc.
Treatment-and-rehabilitation	dietary foods with the improved content of nutrients and adequate caloricity
Signal-motivation	gustatory and extractives (spice, seasoning)

Role of Proteins in Nutrition

Proteins perform a great number of very important functions in the body: structural (construction of tissues), protective (gamma-globulins, etc.), regulatory (hormones, enzymes), transport (hemoglobin of blood), energy (14 % of daily calories).

According to their value, proteins are classified into high-grade and less high-grade.

Attributes of High-Grade Proteins

v Presence in proteins of irreplaceable amino acids at an optimal ratio. By this criterion proteins are placed in the following order: protein of eggs, milk, meat, fish, soya, sunflower.

v Good assimilability of protein in organism. There are 3 groups of proteins:

Ø easily assimilated — milk, fish,

Ø moderately assimilated — meat, eggs (after thermal processing),

Ø badly assimilated — leguminous, bread, mushrooms.

v High biological value. After absorption a greater part of irreplaceable amino acids should be used for the main functions of proteins, except for energy.

Parameters of Protein Value

1. Aminoacidic number (AAN) in %%:

 

The composition of ideal protein (FАО/WHO) in g per 100 g of protein: valine — 5, leucine — 7, lysine — 5.5, isoleucine — 4, methionine — 3.5, threonine — 4, tryptophan — 1, phenylalanine — 6.

AAN of key products: an egg — 100 %, cow milk — 95 %, rice — 67 %, wheat — 53 %.

 

 

2. The ratio of irreplaceable and replaceable amino acids in protein:

 

 

3. Protein efficiency ratio (PER) > 2.5

 

where:

W1 — the initial mass of the body

W2 — mass of an animal body at the end of experiment

В — amount of protein (in g), received by the animal during experiment.

 

 

4. Net protein utilization (NPU) > 0.7

 

A — quantity of nitrogen in meal (in g)

where U — quantity of nitrogen discharged

A with urine (in g)

F — quantity of nitrogen discharged with feces (in g)

      Irreplaceable Amino Acids and Their Functions

Irreplaceable amino acids are not synthesized in a human organism and should be supplied from outside with foods. Among the 20 amino acids eight are irreplaceable for an adult person. They are methionine, lysine, tryptophan, leucine, isoleucine, threonine, valine, phenylalanine.

Methionine. A daily need is 2-3 g. It regulates the exchange of fats, phosphatides and cholesterol — an antisclerotic factor. It is contained in milk, cottage cheese, eggs, legumes, meat, fish.

Lysine. A daily need is 3-5 g. It participates in synthesis of hemoglobin, supports a nitrogenous balance, regulates content of Са in blood. It is contained in milk, meat, fish, soya. Its content in cereals is little.

Tryptophan. A daily need is 1.6 g. It stimulates growth of tissues, synthesis of blood proteins and hemoglobin, maintains a nitrogenous balance. It is contained in little portions in different food proteins.

For children, in addition to above mentioned, 2 more irreplaceable amino acids are necessary — аrginineand histidine. They are conditionally irreplaceable, synthesized in the organism but in insufficient amount for a growing organism, since they stimulate growth, development, metabolism, hematosis.

A Protein Norm and Protein Minimum

A protein norm is a necessary daily amount of protein for a person, which allows the protein to fulfill all its functions. It is a part of the nutrition norms of the population (Table 18). It depends on age, sex, intensity of work. For adults on average it makes up 70-100 g a day. The optimal ratio of animal and vegetable proteins for adults is 50: 50%, for children 60: 40%.

 

Table 18

A Daily Need of Protein (g/kg of body mass)

Country	Men aged 18-59	Women aged 18-59
FAO \ WHO	0.75	0.75
USA	0.80	0.80
Canada	0.77	0.69
England	1.15	1.0
Russia	0.93 — 1.7*	0.96 — 1.4*
Ukraine	0.83 — 1.53*	0.83 — 1.4*

Note: * — depending on age and work intensity

A protein minimum is the necessary amount of protein for maintenance of nitrogen balance in organism — at that all protein is spent on decomposition and formation of nitrogen. Calculation: daily in the organism 6-7g of nitrogen are lost, 1 g of nitrogen is formed at decomposition of 6.25 g of protein (upon the whole about 40 g that is less than 50 % of protein norm). At nutrition on this level the basic functions of protein are not fulfilled, that can result in acquired immunodeficiency.

A Protein Problem and Ways of Its Solving

On a global scale nowadays in the world 50 % of the necessary amount of protein for nutrition of all population of the planet is produced. Almost in all countries, especially in those with an insufficient level of economic development and a low living standard, part of the population experience either shortage of protein in general, or shortage of high-grade (animal) proteins, that affects the population health.

The traditional ways of solving a protein problem are as follows:

· Increase of agricultural production by extensive and intensive ways (at these agrochemicals should be used, that results in contamination of foods and pollution of biosphere)

· Increase of a crop preservation by means of chemicals

· A wide use of protein products of the ocean (but they are very expensive, may cause allergic reactions and accumulate pollutants from the sea water).

· Isolation of protein concentrates from soya, sunflower and their addition to sausages up to 20-30%.

Unconventional ways of solving a protein problem include the following:

· Application of microbiological synthesis (growth of some microbes on sugar production wastes, on oil, but it is very difficult to refine protein from waste products, and such protein cannot be used in man’s nutrition).

· Search of profitable ways of synthesis of irreplaceable amino acids (for the present such chemical synthesis is very expensive).

Role of Fats in Nutrition

The structure of food fats includes: neutral fats (ethers of glycerin and fat acids), fatty substances — phosphatides, mineral substances, fat-soluble vitamins (in some fats).

Functions of fats in nutrition: energy (30-32% of daily calories, 1g fat gives 9 Kcal), regulatory, plastic, protective (from mechanical and temperature effects), gustatory.

Characteristics of Fat Acids

According to the content of free (double) links in formula, fat acids are subdivided into saturated, unsaturated and polyunsaturated.

v Saturated fat acids (SFA) are stearin, palmitic acids in animal fats, butyric and caproic acids — in vegetable oils. They are nonreactive, absorbed worse than others, perform basically an energy function. They are contained in the beef, mutton fat. At excessive use they contribute to the development of atherosclerosis due to plenty of cholesterol and absence of antisclerotic factors.

v Monounsaturated fat acids (MUFA) — oleic acid — contain one free link in the formula; they are better absorbed, perform basically an energy function. They are found in vegetable fats.

v Polyunsaturated fat acids (PUSA) — linoleic, arachidonic acids (omega-6 family), linolenic acid, etc. (omega-3). They have several free links in the formula. They are the most biologically active and valuable among fat acids. They fulfill:

Ø a regulative function, controlling the cholesterol exchange (an antisclerotic factor), reducing coagulability of blood and permeability of vessels.

Ø a protective function, increasing the resistance of organism to infections, toxicants, excess ultra-violet rays (antioxidants).

Ø a plastic function: PUSA are included into vessel walls and myelinic membranes of the nerves.

Suppliers of PUSA: PUSA of omega-6 family are contained in unrefined vegetable oils, PUSA omega-3 are contained in sea fish oils (biologically are most active).

Phosphatide Value

Fatty substances are those in which one fatty acid is replaced by a phosphoric acid and nitrogen base. Their representatives are: lecithin, cephalin. They participate in synthesis of nucleic acids, in cholesterol exchange (an antisclerotic factor). A plastic role is as follows: they are included into cell protoplasm, especially of the nervous system and liver. Suppliers are: liver, brain, egg yolk, butter, lard, unrefined vegetable oils.

Sterols. They are divided into phytosterols and zoosterols (Cholesterol). Despite a widespread opinion about its harm, cholesterol is very important for an organism. Its plastic function is as follows: it is contained in cell protoplasm, creates elasticity of tissues as hydrophylic colloid due to preserving water. A regulative function includes synthesis of vitamin D, bile acids, sex and steroid hormones. A protective function is inactivation of hemolytic poisons.

According to modern concepts the development of atherosclerosis has a multifactorial etiology, which basis is the disturbance of a fatty exchange and increased endogenic synthesis of cholesterol; excess of alimentary cholesterol is of a comparatively small significance — it is an alimentary risk factor of atherosclerosis.

Value of Carbohydrates in Nutrition

Functions of carbohydrates include the following:

· an energy function (56 % of caloric content of a diet per day), 1 g = 4 Kcal

· a regulatory function (a cellular tissue stimulates the motility and secretion of intestines)

· a plastic function (carbohydrates are included in the structure of protoplasm and cellular membranes)

· a protective function (carbohydrates are bound to heavy metals, cholesterol; glucose inactivates cyanides),

· a gustatory function — a sweet taste.

Table 19

Classification of Carbohydrates

CHEMICAL	HYGIENIC
1. Monosaccharides (Glucose, fructose)	1. Unprotected (refined) from absorption
2. Disaccharides (Saccharose, lactose)	2. Protected (starch)
3. Polysaccharides (starch, pectins)	3. Overprotected (Cellulose, pectin substances)

 

In hygiene carbohydrates are subdivided according to degree of absorption:

· The unprotected (refined) carbohydrates aremono- and disaccharides (glucose, lactose, etc.). They are quickly absorbed in the organism and supply energy. At consumption of plenty of such carbohydrates alimentary adiposity, diabetes mellitus and caries may develop.

· To protected carbohydrates starch relates. It is slowly absorbed in organism and supplies most of the energy.

· Overprotected carbohydrates are а cellular tissue, pectin substances.

 

Recommendations for Practical Classes on the Theme

Key Questions

1.Food structure. The basic groups of nutrients.

2.Significance of proteins in nutrition:

concept of a protein norm and protein minimum, signs of full value of proteins and protein products;

irreplaceable amino acids for adults and children; representatives, role in organism, a daily need, foods-suppliers;

3.Significance of fats in nutrition:

- classification of fat acids, representatives, role in organism;

- polyunsaturated fat acids, representatives, their role, foods-suppliers;

- phosphatides, representatives, their role, foods-suppliers;

- cholesterol, functions in organism. Alimentary antisclerotic factors.

4.Significance of carbohydrates in nutrition:

hygienic classification of carbohydrates, representatives;

- hygienic characteristics of various carbohydrates.

Self-control Tests

1. What percentage of total fats should fats of a vegetable origin make up in a balanced diet of an adult man?

* A. not less than 30 %

B. not more than 30 %

C. not less than 50 %

D. not more than 20 %

E. not less than 70 %

2. The signs of full value of proteins include the following:

* A. an optimal ratio of irreplaceable amino acids

B. convenience of thermal processing without loss of food value

* C. good assimilability

* D. high biological value

E. performance of energy function

3. Identify the alimentary antisclerotic factors.

* A. methionine

B. lactose

* C. PUSFA

D. vitamin C

* E. phospholipids

Problem Solving

1. Suffering from bilateral pneumonia, patient N. received intensive antibacterial therapy, which resulted in dysbacteriosis of intestines. What changes expedient to the diet of the patient will you recommend?

2. What foods are the prevailing source of phospholipids?

3. Energy losses of a miner aged 35 make up 4,100 Kcal. The analysis of a daily food allowance has shown that its caloricity is equal to 3,640 Kcal. It contained proteins — 100 g, fats — 90 g, carbohydrates — 598 g. Dietary habits provide four meals a day: breakfast — at 6.00, lunch — at 11.00, dinner — at 16.00, supper — at 20.00. Caloricity is distributed by meals: breakfast — 20 %, lunch — 15%, dinner — 40 %, supper — 25 %. Determine the group of work intensity, estimate value of nutrition, balance of the diet and dietary habits.

Standard Answers:

1. It is necessary to increase the amount of dairy products (kefir, yoghurt, acidophilin) in the diet.

2. Cereals, oil, leguminous cultures.3. The 4th group of work intensity. Daily caloricity should make up 3,900-4,300 Kcal. The diet meets to principles of balanced meals.

 

Theme No 6.

The Significance of Vitamins and Minerals in Nutrition

Value of Vitamins in Nutrition

Vitaminsare the low-molecular organic substances, biologically active in very small amounts.

Functions of vitamins:

· regulatory — they form enzymes and regulate metabolism,

· protective — they increase the resistance of organism to the unfavourable climatic factors, harmful physical and chemical influences, infections, etc. (vitamin C is an antioxidizer).

Classification of Vitamins

Water-Soluble Vitamins

Vitamin C — Ascorbic acid

Vitamin В1 — Thiaminum

Hepatoflavin — Riboflavinum

Vitamin В3 or В5 — pantothenic acid

Vitamin B6 — pyridoxine, pyridoxal, pyridoxamine

Vitamin В12 — cyanocobalamin

Vitamin Н — biotin

Vitamin РР — Niacin, nicotinamidum

Folic acid

Liposoluble Vitamins

Vitamin A — Retinolum, retinolacetat, retynal

Vitamin D — ergocalciferol (D2), cholecalciferol (D3)

Vitamin E — admixture of tocopherols

Vitamin K — admixture of naphthoquinones

Vitamin-like Substances

Choline

Inosite — Vitamin B 8

Lipoic acid — Vitamin U

Orotic acid — Vitamin B 15

Pangamic acid — Vitamin В15

Carnitine

Para-aminobenzoic acid

Biologically fissile materials — Bioflavonoids

 

       Sources of vitamins

Vitamins are formed basically in plants, and also accumulate in animal organisms. A person receives water-soluble vitamins with vegetable food, fat-soluble ones — with animal and vegetable food.

Some vitamins can be synthesized in a human organism:

· Vitamins of group B, especially B12, are formed in intestines at microflora activity;

· Calciferoles (vitamin D3 — cholecalciferol) are formed in the skin from provitamin dehydrocholesterol at ultra-violet irradiation.

· Vitamin A (retinol) is formed from beta-carotenes of vegetable food in very insignificant amounts (1/6 of need for vitamin A).

 

Types of Vitamin Status of Organism

By level of vitamin supply of organism the following are distinguished:

· Avitaminosis — a complete absence of vitamin in nutrition for a long time;

· Hypovitaminosis — insufficient supply of organism with vitamins (about 50 % of requirement);

· Subhypovitaminosis — a boundary condition between hypovitaminosis and a normal vitamin state;

· Normal supply of organism with vitamins;

· Hypervitaminosis — an excess intake of vitamins (vitamins A and D, as a rule).

Avitaminosis and hypovitaminosis can be exogenic and endogenic (the latter is caused by disturbance of vitamin absorption).

Methods of diagnostics of vitamin status are as follows:

· According to symptomatology of disturbances, characteristic of each avitaminosis connected with a concrete vitamin (scurvy, beriberi, etc.).

· Biochemical methods (by content of vitamines in blood or urine and comparing the results with the norm).

· Functional tests (skin haemorrhage at vitamin C hypovitaminosis).

 

Factors influencing the vitamin requirement of organism are divided into:

v Exogenic:

Ø a phsychoemotional and physical overstrain

Ø work at high and low temperature

Ø work in mines, in the Far North

Ø contact with industrial poisons, at medicine intake (antibiotics)

Ø work with radiation, noise, vibration

Ø smoking

Ø seasonal fluctuations — insufficient amount of vitamins in a diet in winter and spring.

v Endogenic:

Ø age

Ø pregnancy and lactation

Ø infectious diseases

Ø endocrine diseases (hyperthyroidism, increase of metabolism in organism)

Ø intestinal diseases (disturbance of vitamin absorption, resection of intestines).