HUMAN BIOCHEMISTRY - L. V. Kapilevich - 2016

PART 1. SPORTS BIOCHEMISTRY

BIOCHEMICAL BASES OF NUTRITION

The diet must qualitatively and quantitatively meet the body's demand for substances required for Cells and Tissues to synthesize their own structures essential for vital processes, as well as for adaptive and defensive reactions.

Organic and inorganic substances supplied with food serve as the Starting Material for building living tissue and its continuous renewal, as well as the sole source of energy for humans and animals.

Principles of Diet Planning

Based on METABOLISM/2.html">THE CONCEPT OF rational balanced Nutrition developed by A. A. Pokrovsky and other scientists, planning a diet (i.e., the daily quantity and composition of food products required by an individual) should follow several key principles:

1. The caloric intake of the diet must correspond to the body's Energy Expenditure across all types of life activities.

2. The Nutritional Value of food components must be taken into account. The diet should contain an optimal amount of Proteins, fats, CARBOHYDRATES, minerals, Vitamins, and Water for a given individual or professional group.

3. It is important to properly distribute the caloric intake among individual meals throughout the day in accordance with biorhythms, as well as the schedule and nature of work and other activities.

4. Applying technological Processing Methods that ensure the removal of harmful substances without reducing the Biological value of food or leading to The formation of toxic products.

5. Ensuring the organoleptic qualities of food to facilitate its Digestion and assimilation.

6. The presence of dietary fiber in the diet to help eliminate toxic Metabolic waste products from the body.

Caloric Value of the Diet

The energy reserve in food is determined using a bomb calorimeter—a closed chamber immersed in a water bath. A precisely weighed sample is placed inside the chamber, filled with pure oxygen, and ignited. The amount of released energy is measured by The change in Temperature of the water surrounding the chamber.

During oxidation:

✵ 1 g of carbohydrates yields 17.17 kJ (4.1 kcal);

✵ 1 g of fat yields 38.96 kJ (9.3 kcal);

✵ 1 g of protein yields 22.61 kJ (5.4 kcal).

An overly scarce diet, in which the ENERGY VALUE OF the daily ration does not cover the energy expended during the day, leads to a negative Energy balance. In this case, the body mobilizes all its resources to cover the resulting energy deficit. First, the body begins to use all incoming nutrients, including proteins, as an energy source, and second, it starts burning stored energy reserves—not only fat, but also tissue protein, which leads to The Development of Protein deficiency.

A positive energy balance, where the caloric content of the daily diet significantly exceeds energy expenditure, also leads to unpleasant consequences: the development of obesity and related diseases such as atherosclerosis, Hypertension, and many others.

Thus, both positive and negative energy balances adversely affect health, causing Metabolic Disorders and functional and morphological changes in various body systems.

Any human activity is accompanied by energy expenditure; the amount of energy required for various types of activities is presented in Table 3.

Class="center">Table 3. Human energy expenditure during various activities

In addition, There is a conventional Classification of labor activity, where each type corresponds to a specific daily energy expenditure (Table 4).

Table 4. Daily energy expenditure According to the type of labor

Dietary Balance

Modern data on the body's nutrient requirements and the interplay between them are summarized in The Theory of balanced nutrition. According to this concept, optimal nutrient assimilation and overall bodily function require an intake of all essential nutrients in specific proportions.

When evaluating a diet, its balance across multiple parameters is taken into account. For instance, the standard ratio of proteins, fats, and carbohydrates is considered to be 1:1,1:4.1 for young men and women engaged in mental work, and 1:1.3:5 for those performing heavy physical labor. In these calculations, the amount of protein is taken as a unit.

When assessing protein balance, it is taken into account that animal-derived proteins should account for 55% of the total protein intake. Vegetable oils, serving as sources of Essential Fatty acids, should comprise up to 30% of the total dietary fats. The approximate carbohydrate balance is as follows: starch — 75-80%, easily digestible carbohydrates — 15-20%, and dietary fiber and Pectins — 5% of the total carbohydrates. The recommended balance of essential vitamins per 4.184 mJ (1000 kcal) of the diet is: Vitamin C — 25 mg, B1 — 0.6 mg, B2 — 0.7 mg, B6 — 0.7 mg, and PP — 6.6 mg. These values are higher in clinical nutrition.

The optimal ratio of calcium, phosphorus, and magnesium for assimilation is 1:1.5:0.5.

The vitamin and mineral content of staple foods is presented in Table 5.

Table 5. Vitamin and mineral content in staple foods (mg per 100 g of product)

Dietary Regimen

To ensure that absorption processes occur at maximum intensity and that the body can fully utilize the ingested nutrients, it is necessary not only to tailor the diet to age and activity type, but also to maintain a proper eating schedule.

Meals should be taken at scheduled times. This is of great importance because the secretory activity of the digestive glands begins even before food is consumed. Failure to follow a regular eating schedule disrupts this well-established digestive function. For an adult, four meals a day is considered most optimal, or at least three meals. The higher the caloric content of the diet, the greater the meal frequency. For athletes, six to eight meals a day are permissible.

With a three-meal schedule, which is acceptable for an adult, food should be distributed as follows: breakfast should account for 30% of the daily calorie intake, lunch for 45-50%, and dinner for 20-25%. For a four-meal schedule, the distribution should be: first breakfast — 25%, second breakfast — 10%, lunch — 45%, and dinner — 20% of the daily intake.

Nutritional Features for Athletes

The Role of nutrition in training elite athletes cannot be overstated. Modern sports records demand a corresponding level of preparation. Increased training loads, intense competition schedules, frequent changes in climate zones and time periods, training in mid-altitudes, as well as advanced technical equipment — all these elements define elite sports and require tremendous physical and mental effort from athletes. A rational, balanced diet is one of the most critical components in ensuring a high level of functional readiness in athletes. Diets recommended for competitors in various sports disciplines are tailored to their training phase, season (Energy Requirements are approximately 10% higher in winter), climatic conditions, age, gender, body weight, sports experience, and other individual parameters. Furthermore, an athlete's diet must:

1) correspond to their current energy expenditure;

2) be balanced, meaning it must contain all essential nutrients (proteins, fats, carbohydrates, vitamins, mineral salts, BIOLOGICALLY ACTIVE SUBSTANCES) in the correct proportions;

3) include foods of both animal and plant origin;

4) be easily digestible by the body.

Food preparation and culinary processing are vital aspects of athletic diets. Particular attention should be paid to preserving the natural properties of foods to the maximum extent, ensuring variety, and providing appealing presentation. For elite athletes, 4 to 5 meals a day are preferred.

The caloric content of the diet must match the athlete's energy expenditure, which in turn depends on age, gender, sports experience, qualification level, and, above all, the specific sport. The quantitative ratio of Macronutrients varies strictly among athletes of different disciplines, depending on The Nature of their training and competitive activities. Table 6 presents the daily requirements for energy and major nutrients per 1 kg of body weight for various sports. Athletes specializing in endurance sports are recommended a diet where proteins provide 14-15% of energy expenditure; for speed-strength sports, this figure is 17-18%, and in certain cases up to 20% (bodybuilding, weightlifting).

Table 6. Daily requirements for energy and major nutrients per 1 kg of body weight for various sports

Protein intake exceeding 3 g/kg is not recommended even for athletes in disciplines such as weightlifting, throwing, and bodybuilding, as the body is generally unable to cope with breaking down and assimilating such a massive amount of protein. Conversely, inadequate protein intake (less than 2 g per kg of body weight) fails to support normal metabolic processes, potentially leading to increased excretion of essential vitamins—such as vitamin C, thiamine, riboflavin, pyridoxine, and niacin—as well as potassium salts. Alongside their plastic (structural) function, Proteins can also serve as an energy source for the body. Specifically, 10–14% of ingested protein can be oxidized to supply necessary energy. In this regard, specific demands are placed on the quality of consumed protein, its amino acid profile, and the presence of Essential Amino Acids (Table 7).

Table 7. Recommended daily intake of essential amino acids (in mg per kg of body weight)

It is generally considered optimal for the diet to contain 55–65% of proteins of animal origin.

Prior to intense training sessions and competitions, dietary fat content should be reduced, as fats are poorly digested under high physical and emotional stress. During periods of maximal and submaximal exertion, the body's energy supply is sustained primarily by carbohydrates; fructose is recommended for carbohydrate loading. Its advantage over glucose is that fructose intake does not cause significant fluctuations in Blood sugar (glucose) levels and therefore does not trigger an excessive Insulin spike from the Pancreas. Furthermore, Glycogen depletion in skeletal Muscles is significantly lower when fructose is consumed compared to glucose.

One of the Key Components of A balanced diet is obtaining adequate amounts of VITAMINS AND MINERALS through food (or via pharmacological supplements). It is worth noting that the values presented in Table 8 are 1.5–2 times higher than the figures reported by American authors, which is likely due to differences in dietary patterns and food quality in the United States.

The Need for supplemental vitamins (beyond those found in food) by no means implies that higher doses will enhance athletic performance. On the contrary, vitamin overdoses can lead to severe adverse health consequences.

Table 8. Daily Vitamin Requirements for athletes across various sports disciplines (in mg)

Thus, it can be safely concluded that a complete, balanced diet is one of the most critical elements in the biomedical support of training and competitive performance. For rational pharmacological support, the interaction between medications and food components, as well as the optimal timing of administration, is of utmost importance. Key factors influencing drug dissolution and absorption include the composition and temperature of food, as well as the presence of healthy intestinal microflora.

Medications are frequently mixed with fruit or vegetable juices in an attempt to mask an unpleasant taste or make them easier to swallow. However, juices contain various organic acids that can break down certain compounds, particularly Antibiotics. As a general rule (unless otherwise specified), medications should be taken on an empty Stomach; this prevents interactions between drugs and food components, significantly limits the Adverse effects of digestive juices, and eliminates the food-induced delay in drug absorption. This ensures maximum bioavailability of pharmacological agents for the body. Choleretic agents are best administered 5–10 minutes before a meal so that they stimulate Bile secretion just as food enters the duodenum. Post-meal administration is generally recommended for water-insoluble, fat-soluble drugs (such as Fat-soluble vitamins A, D, E, and K), as well as preparations containing potassium, bromine, or sodium salts, and reduced iron. Taking medications before meals may occasionally cause irritation of the gastric mucosa, which can be mitigated by washing the medicine down with water, starch mucilage, or milk.

Review Questions

1. What is the role of nutrition?

2. List the principles of a rational diet.

3. What methods are used to determine the caloric content of food?

4. What does the term "basal metabolic rate" mean?

5. What methods can be used to assess human energy expenditure?

6. What is the recommended daily protein intake for athletes?

7. Is it possible to completely eliminate dietary fats?

8. Which Organic compounds are the most efficient Energy Sources?

9. Why is the consumption of dietary fiber (ballast substances) necessary?

10. What factors determine the frequency of meals per day?

11. What are the reasons for specialized diets in athletes?

12. What requirements must an athlete's diet meet?

13. What factors determine an athlete's energy expenditure?

14. What is the optimal quantitative ratio of the main nutritional components for sports such as gymnastics, marathon running, and cycling?

15. Why is there a limit on the amount of protein that can be consumed?

16. Which Amino acids are classified as essential?

17. Why is it preferable to consume fats of plant origin and dairy fats?

18. What is recommended to wash down medications with?