HUMAN BIOCHEMISTRY - L. V. Kapilevich - 2016

PART 1. SPORTS BIOCHEMISTRY

VITAMINS

Vitamins are low-molecular-weight Organic compounds required in small amounts for the normal functioning of the body. The Human Body cannot synthesize most of these substances, and until recently, they were obtained solely from food. Some vitamins are produced in limited quantities by the intestinal microflora.

The Role of vitamins in the human body

Vitamins play a vital role in ensuring the normal functioning of the human body. They act as biocatalysts for Chemical Reactions involved in building and constantly renewing the body's living structures and in regulating METABOLISM.

The body's requirement for vitamins

The body requires vitamins in amounts ranging from several micrograms to several milligrams (Table 1).

A deficiency of vitamins in food or altered absorption processes leads to Metabolic Disorders and, ultimately, to hypovitaminosis and avitaminosis. An excessive intake of vitamins results in a condition known as hypervitaminosis (Table 2).

Avitaminosis refers to the virtually complete absence of a specific vitamin in the body, manifesting as distinct symptom complexes such as scurvy or pellagra. Hypovitaminosis is defined as a vitamin content in the body that is lower than required. Clinically, hypovitaminosis manifests only through isolated, mild symptoms specific to a particular avitaminosis, as well as nonspecific general symptoms common to various types of hypovitaminosis (e.g., decreased appetite and performance, rapid fatigue). A deficiency of several vitamins simultaneously is referred to as polyhypovitaminosis.

Classic avitaminoses are very rare, occurring mainly under conditions of prolonged starvation, where vitamin deficiency accompanies nutritional marasmus; during forced, drastic reductions in dietary variety (e.g., when food delivery is impossible for remote expeditions or encircled troops); with the intake of large amounts of Antivitamins; and in certain hereditary enzymopathies or severe Digestive System disorders accompanied by malabsorption syndrome.

Class="center">Table 1. Daily requirement of an adult for vitamins and mineral elements

Table 2. Some potential side effects of excessive vitamin intake

Hypovitaminoses are much more common. In addition to the factors listed above, their causes may include prolonged parenteral Nutrition, irrational Chemotherapy, chronic intoxications (including infectious diseases), and malignant neoplasms. Furthermore, The Development of hypovitaminosis is promoted by the widespread dietary use of refined foods stripped of vitamins during Processing (fine-milled bread, sugar, etc.); the loss of vitamins during prolonged storage and improper culinary preparation; and the trend toward replacing fresh foods with canned goods in home cooking. Vitamin deficiency reduces the body's adaptive capacity, resulting in lower Resistance to Infectious and toxic factors, decreased physical and mental performance, delayed recovery from acute illnesses, and an increased likelihood of chronic disease exacerbations.

Classification of Vitamins

All vitamins are divided into Water-soluble and fat-soluble.

Brief Characteristics of Individual vitamins

Water-soluble

Vitamin B1 (thiamine) promotes the active utilization of Proteins, fats, and CARBOHYDRATES in metabolism. It plays an active role in regulating Cardiac Activity and bowel function, and is highly important in Lipid Metabolism by synthesizing Fatty acids. Vitamin B1 hypovitaminosis impairs the function of both The Heart Muscle and the Central Nervous system. This vitamin is abundant in coarse-ground flour (especially rye bread), potatoes, legumes, cabbage, and in animal-derived foods such as Kidneys, Liver, and Brain.

Vitamin B2 (riboflavin) is paramount for regulating digestive function and, in combination with vitamin A, Vision. This vitamin also actively influences protein and Carbohydrate Metabolism. Hypovitaminosis B2 leads to stunted GROWTH AND DEVELOPMENT, Hair loss, inflammation of the mucous membranes of the eyes and Oral Cavity, anemia, and impaired liver function. Vitamin B2 is abundant in dairy products, meat, liver, kidneys, heart, egg yolk, mushrooms, and nutritional Yeast. It is also found in vegetables and fruits.

Vitamin B3 (niacin) lowers Cholesterol levels, AIDS in the assimilation of proteins, fats, and sugars, reduces high Blood pressure, Supports The Nervous System and gastrointestinal tract, maintains healthy Skin, prevents diseases such as pellagra, and enhances physical performance. It is found in meat, milk, eggs, fish, poultry, and grains. Deficiency leads to dizziness, weakness, and gastrointestinal disorders.

Vitamin B5 (also known as PP or nicotinic acid) is actively involved in cellular Respiration, stimulates cellular metabolism, enhances digestive enzyme activity, and participates in Blood Coagulation mechanisms. A deficiency of this vitamin leads to inflammatory and degenerative skin changes, up to the development of pellagra. The digestive system is severely affected, with chronic diarrhea being one of the distressing symptoms. Nervous system damage manifests as various neuropsychiatric disorders. Hypovitaminosis PP typically occurs in monotonous diets. Foods rich in this vitamin include nutritional yeast, meat, liver, legumes, buckwheat and pearl barley, potatoes, nuts, cheese, as well as rye bread, milk, and cabbage.

Vitamin B6 (pyridoxine) regulates metabolic processes in the nervous system, skin, and liver. Its deficiency in the body results in general weakness, increased fatigue, neurasthenic symptoms, and difficulty walking. The main dietary sources of vitamin B6 are grains, yeast, meat, egg yolk, and many fresh vegetables.

Vitamin B12 (cyanocobalamin) is an essential component required for the normal synthesis of a range of Amino Acids. It plays a vital role in hematopoiesis, particularly in red blood Cell maturation and blood clotting, and significantly impacts carbohydrate and lipid metabolism. Hypovitaminosis B12 leads to anemia caused by a sharp decline in red blood cell count. Rich sources of vitamin B12 include liver, meat, eggs, fish, fermented dairy products, and yeast.

Vitamin B15 (calcium pangamate) positively influences lipid metabolism, improves Tissue and organ oxygenation, and regulates muscular and hepatic function. It exhibits anti-sclerotic properties and is found in a variety of foods.

Vitamin C (ascorbic acid) activates digestive Enzymes and is strictly necessary for the growth and Development of the young body. It plays an active role in the synthesis of various Hormones and regulates the acid-base balance of the blood, while also having a major function in vascular regulation and carbohydrate metabolism. A deficiency in vitamin C reduces work capacity and immune defense, making the body susceptible to infections; in severe cases, it causes scurvy. Rose hips, black currants, lemons, and many other vegetables, fruits, and berries are exceptionally rich in vitamin C. It should be emphasized that vitamin C is sensitive to culinary processing, rapidly breaking down under excessive heat, prolonged storage of salted and pickled vegetables, as well as in compotes and preserves. Therefore, vegetables, fruits, and berries are best consumed fresh. When boiling, it is recommended to drop them into boiling water and cook in a tightly covered pot.

Fat-soluble

Vitamin A participates in phosphorus metabolism, promoting the proper development and formation of bones—a process of utmost importance during youth, which is why this vitamin is often referred to as the growth vitamin. It also maintains the health of the skin and mucous membranes and stimulates pancreatic function. This vitamin is essential for normal vision and is known to regulate lipid metabolism. A Vitamin A deficiency quickly disrupts metabolism, leading to skin conditions such as furunculosis and eczema, impairs vision, and lowers Immunity, resulting in a heightened Susceptibility to infectious diseases.

Vitamin D plays an active role in Mineral Metabolism—primarily Calcium and phosphorus—which is particularly crucial for children, earning it the alternative name of anti-Rickets vitamin. Its deficiency in children leads to rickets and impairs parathyroid gland function, resulting in skeletal abnormalities. Butter, whole milk, egg yolks, fish oil, and the liver of cod and other fish are exceptionally rich in vitamins D and A. Additionally, vitamin D can be synthesized in the body under The Influence of ultraviolet solar radiation, whereas vitamin A is synthesized in the human liver from carotene (provitamin A), which is abundantly found in carrots, spinach, lettuce, tomatoes, sorrel, and rose hips.

Vitamin E (tocopherol) is also known as the reproduction vitamin because it exerts a regulatory effect on sexual development, particularly during the prenatal stage. It is found in varying amounts in both animal-derived products and leafy greens.

Vitamin K regulates blood clotting by acting on the liver to stimulate the synthesis of relevant enzymes. A deficiency in vitamin K impairs prothrombin formation, significantly increasing the predisposition to hemorrhaging. Foods rich in this vitamin include cabbage, other leafy greens, rowan berries, carrots, and tomatoes.

Self-Assessment Questions

1. What is the Biological Role of vitamins?

2. Into what two groups are vitamins divided?

3. What is the difference between avitaminosis and hypovitaminosis?

4. List the causes of hypovitaminosis.

5. Can vitamins be consumed in unlimited quantities?

6. In which human body processes does vitamin B12 participate?

7. Which foods contain high amounts of vitamin K?

8. Which Vitamins can be synthesized in the human gut, and under what conditions?