Vitamins are a group of low molecular weight biologically active substances that are involved in the regulation of many biochemical reactions and body functions. Vitamins are not formed in the human body or are formed in small quantities, so they are considered essential nutrients.
The number of known vitamins of direct importance for nutrition and health reaches twenty. All of them are of great importance in the regulation of metabolism and physiological functions. The daily human need for vitamins is a few milligrams or micrograms and depends on age, gender and level of physical activity. Only vitamins C and P are needed by the body in large quantities – up to 100 mg of vitamin C and 30 mg of vitamin P. For athletes, the daily intake of vitamins is increased by 2-4 times, which is associated with the intensification of metabolism during training.
The action of many vitamins on metabolism is interconnected with enzymes. Therefore, the high activity of enzymes and their effect on the metabolic rate depends on the provision of the body with vitamins. Depending on the availability of vitamins, it is customary to distinguish such conditions of the body as beriberi, hypovitaminosis and hypervitaminosis.
Avitaminosis is a specific metabolic disorder caused by a prolonged absence (deficiency) of any vitamin in the body, which leads to a certain disease or death of the body. Hypovitaminosis is a condition of the body associated with an insufficient (reduced) amount of vitamins in the body. It manifests itself in rapid fatigue, decreased efficiency, visual acuity in the dark, peeling of the skin, and a decrease in the body’s resistance to infectious diseases. Hypervitaminosis is a violation of biochemical processes and functions due to excessive (long-term) intake of vitamins in the body. Hypervitaminoses are characteristic of fat-soluble vitamins, especially A and D, which can accumulate in the body’s fat depots. The causes of hypo- and avitaminosis in humans may be dietary disturbances or absorption of vitamins in the intestines, their undersupply in case of increased demand, for example, during strenuous exercise. Hypovitaminosis can most often be observed at the end of winter and in spring, when Vitamins are depleted in food.
Vitamins are divided into two groups: fat-soluble (A, D, E and K) and water-soluble (C, P, H, vitamins of group B, etc.).
Fat soluble vitamins
Vitamin A (retinol) is found in animal products such as animal and fish liver, butter, egg yolk, and plant products, especially in various types of vegetables (carrots are most famous in this regard). Fruits and fruits also contain provitamin A (carotene).
Vitamin A is necessary for the growth process, ensuring normal vision. It promotes the growth and regeneration of the skin and mucous membranes. In the absence of this vitamin, drying and keratinization of tissues occurs, as a result of which infections often develop. Damage to the cornea and connective tissue of the eyes can lead to complete loss of vision.
Vitamins of group D (calciferols) are found in fish products, to a lesser extent – in dairy products. Under the influence of sunlight, the body itself can synthesize this vitamin from certain precursors – provitamins. Vitamin D regulates the exchange of calcium and phosphorus, promotes their absorption from the intestines and deposition in the bones. Deficiency of this vitamin in children leads to rickets.
Vitamin E (tocopherol) is found in significant quantities in vegetable oils, the germs of cereal seeds (barley, oats, rye and wheat), as well as in green vegetables. Vitamin E is one of the most powerful antioxidants, i.e. Protects cell membrane lipids and fatty acids from excessive peroxidation, preserving their biological functions. It affects the function of the sex and other endocrine glands, maintains the elasticity of blood vessels, reduces blood clotting, enhances protein synthesis in skeletal muscles, showing an anabolic effect.
Vitamin K (phylloquinone) is found in vegetables (spinach, green peas, etc.), fish, meat. Vitamin K is part of the enzymes that regulate blood clotting processes. Insufficiency of this vitamin in a person can occur when there is a violation of resorption (absorption) in the gastrointestinal tract (for example, in diseases of the liver and gallbladder) or the cessation of its synthesis by intestinal bacteria. The lack of vitamin K is manifested mainly in the occurrence of bleeding, so how this vitamin is involved in the formation of an important substance for blood coagulation – prothrombin.
Water Soluble Vitamins
From the group of water-soluble vitamins, consider the B vitamins, vitamin C and bioflavonoids (vitamin P).
Vitamin B1 (thiamine) is found primarily in the germs and seed coats of cereal crops, in yeast, nuts, legumes, as well as in some animal products – heart, liver, kidneys. Black bread is a rich source of this vitamin.
Vitamin B1 is involved in the regulation of carbohydrate metabolism. It is part of the enzymes involved in the biosynthesis of nucleic acids. He also takes part in the transformation of amino acids, is involved in protein and fat metabolism. Therefore, with an increase in the intake of carbohydrates in the body, the need for this vitamin increases. The same happens with an increase in the intensity of energy metabolism. Deficiency of this vitamin causes severe disorders of the nervous system (polyneuritis).
Vitamin B2 (riboflavin) is found in significant amounts in the liver, kidneys, yeast, and dairy products. This vitamin is involved in the processes of tissue respiration, is part of the enzymes that regulate the most important stages of metabolism. With β-avitaminosis, the processes of tissue respiration are weakened, which causes growth retardation, increased breakdown of tissue proteins, a decrease in the number of leukocytes in the blood, and dysfunction of the digestive organs. An increase in the amount of carbohydrates and fats in the diet leads to an increase in the need for riboflavin.
Vitamin B6 (pyridoxine) enters the body in the composition of foods such as wheat flour, legumes, yeast, liver, kidneys and some others, and is also produced by intestinal microbes. Being a part of transaminase enzymes that catalyze the transamination of amino acids, pyridoxine plays an important role in protein metabolism. Vitamin Wb is also of great importance in the metabolism of fats (lipotropic effect), in hematopoiesis, in the regulation of acidity and gastric secretion. Manifestations of vitamin Wb deficiency are growth retardation, dermatitis, memory impairment, and a decrease in the number of lymphocytes in the blood. A person’s need for vitamin Wb increases with an increase in the amount of protein in the composition of food, as well as during physical exertion.
The B vitamins also include nicotinic acid or niacin (vitamin PP). A person receives nicotinic acid in bread, in various cereals, liver, meat, fish. Vitamin PP is part of the most important enzymes that catalyze the processes of tissue respiration by transferring hydrogen. Lack of nicotinic acid causes pellagra – a disease that manifests itself in a combination of dermatitis, intestinal dysfunction and mental pathology.
Vitamin B12 (cyanocobalamin) enters the human body as part of animal products (liver, kidneys, fish). Cyanocobalamin increases the number of red blood cells, is involved in the synthesis of nucleic and amino acids. This leads to the activation of protein synthesis, growth and recovery processes. In case of violation of the absorption of vitamin Bp, anemia develops, which is associated with inhibition of the formation of red blood cells.
Vitamin C (ascorbic acid) is found mainly in fresh vegetables and fruits. Rich sources of this vitamin are rose hips, black currants, citrus fruits, dill, sweet peppers, parsley, spinach, tomatoes, cabbage. Grinding and long-term storage, cooking and canning of these products significantly reduce their vitamin C content.
Ascorbic acid is involved in redox processes. It is necessary for normal protein metabolism, for the formation of connective tissue, including in the walls of blood vessels, for the synthesis of steroid hormones of the adrenal glands, which play an important role in the body’s adaptation to stressful situations, etc.
C-vitamin deficiency causes a serious disease (scurvy), which is characterized by hemorrhages (due to increased fragility and permeability of the walls of blood vessels), a decrease in physical performance, a weakening of the function of the cardiovascular system, etc.
The need for ascorbic acid during intense muscular activity increases significantly. To increase physical performance, an increased supply of this vitamin to the body is necessary. However, its long-term consumption in quantities significantly exceeding the normal requirement can lead to the body becoming addicted to increased doses. In this case, when returning to the usual, normal amounts of vitamin C in the diet, phenomena of its deficiency may occur.
Vitamin P (rutin) belongs to bioflavonoids, the total number of which reaches one hundred and fifty. Vitamin P is found in plant foods. Much has been established in the action of vitamins C and P. Vitamin P is also involved in redox reactions and stimulates tissue respiration. It has a capillary-strengthening effect and the ability to reduce the permeability of vessel walls. Lack of vitamin P in the diet causes capillary fragility, hemorrhage. Vitamin P enhances the reduction of dehydroascorbic acid to ascorbic acid.
Recently, ideas about the role of vitamins in the body have been enriched with new data. It is believed that vitamins are able to improve the internal environment, increase the functionality of the main systems, the body’s resistance to adverse factors. Consequently, vitamins are considered by modern nutritional science as an important means of general primary prevention of diseases, increasing efficiency, and slowing down the aging process.