Vitamin D.

Vitamin D belongs to the group of vitamins that the human body can synthesize on its own under certain conditions: the presence of the sterol group provitamins (sitosterol, stigmasterol, ergosterol) supplied with plant food, the 7-dehydrocholesterol provitamin, which is formed in the tissues of the person himself from cholesterol and a sufficient amount of sunshine. rays. In addition to these conditions, the age of a person matters, since aging skin (namely, the synthesis process takes place in it) gradually loses its ability to synthesize vitamin D, and the amount of melanin contained in the skin and giving it a tanned appearance reduces the synthesis of vitamin D, due to the fact that melanin has the ability to filter UV radiation.

Synthesized in the skin and ingested with food, vitamin D is absorbed by the cells of the small intestine in the presence of enzymes and enters the various structures of the body in the form of metabolites and catalysts (vitamins). In the liver, vitamin D is hydroxylated, resulting in the formation of the compound 25-oxyvitamin, which is then hydroxylated in the kidneys to 1,25-dioxycholecaciferol (this is an active metabolite of vitamin D that mimics the work of a hormone, which is why vitamin D is sometimes called hormone-D). A unique feature of the 1,25-dioxycholecaciferol metabolite is its ability to influence the reabsorption of calcium in muscle tissue and kidneys by stimulating the protein that transports calcium ions and stimulating the transcription of DNA and RNA.

The synthesis of the 1,25-dioxycholecaciferol metabolite is regulated by parathyroid hormone, the concentration of which, according to the principle of reverse interaction, is influenced by the level of the 1,25-dioxycholecaciferol metabolite itself and the concentration of calcium ions in the blood plasma. This is a very complex relationship, the violation of which leads to a number of severe conditions: hypothyroidism, hyperthyroidism.

The main function of vitamin D in the body is to regulate bone mineral metabolism and maintain the properties of bone tissue, which ensure the formation and growth of the skeleton.

Vitamin D regulates the metabolism of calcium, phosphorus and magnesium ions. By creating favorable conditions for absorption in the small intestine. It is vitamin D that maintains the level of calcium and phosphorus in the blood plasma until the concentration of these elements is exceeded, therefore, an excess of vitamin D can be dangerous, since it provokes hypercalcemia.

The benefits of vitamin D in maintaining the health of the body are multiple:

Regulates bone mineralization and prevents osteomalacia, osteoporosis;
Prevents the development of a state of hypocalcemia;
Provides favorable conditions for the functioning of the cardiovascular system (affects the state of the myocardium, arterial hypertension);
Provides a normal state of neuromuscular fibers, thereby preventing the development of diseases such as multiple sclerosis, convulsive syndromes, myopathies;
It has a beneficial effect on the condition of the skin, slowing down the processes of increased keratinization (especially in cases of skin diseases);
Provides the right conditions for digestion;
Responsible for the strength of tooth enamel, nails and the normal condition of hair;
Regulates global metabolic processes in the cells of the body, preventing the development of pathological conditions in the kidneys, liver, intestines, bladder, mammary glands;
It forms the basis of osteogenesis and is responsible for the correct formation of the human skeleton throughout his life.

Lack of vitamin D leads to the development of hypovitaminosis D, which is reflected in disorders of the structure and growth of bone tissue (rickets, curvature of the spine and other bones of the skeleton, osteoporosis), indigestion, formation of tissues of teeth, nails, hair, disorders in the functioning of the neuromuscular apparatus (osteomyelitis ), metabolic disorders (type 2 diabetes mellitus). Experimental studies also provide evidence on the development of breast, endometrial, kidney, colorectal, ovarian, esophageal cancer and other cancers with reduced levels of vitamin D in the body.

Sources of vitamin D, in addition to its natural synthesis in human skin, are provitamins synthesized by plants and vitamin synthesized by animals:

Plants food:

Parsley, Alfalfa, Nettle, Horsetail, yeast, molds contain ergosterol - a vitamin D provitamin,
Oats (up to 200 IU / 100g),
Rice (up to 170 IU / 100g).

Animals food:

Fish oil (cod, salmon, mackerel, herring) (up to 800 - 1600 IU / 100g),
Egg yolk (25 - 100 IU / 100g),
Butter (up to 35 IU / 100g),
Cheese (up to 7 IU / 100g),
Sour cream (up to 50 IU / 100g),
Liver (pork, beef) (up to 50 IU / 100g).

The body's daily need for vitamin D:

For an adult healthy person, it is 100 IU,
For healthy adolescent children, it is 400 IU,
For healthy newborns, it is 400 IU,
For healthy pregnant women, it is 400-500 IU.

If it is necessary to change the dose of vitamin D intake per day, this issue is discussed with the doctor, taking into account analyzes of the level of calcium and phosphorus in the blood plasma and under the control of these indicators.

In 2013, the ESCEO (European Society for the Clinical and Economic Aspects of Osteoporosis and Osteoarthritis) recommendations were published on the prescription of vitamin D, which indicated the safe limits of vitamin D intake per day: the norm of 800-1000 IU, with osteoporosis and overweight of 1500-2000 IU ... The total intake of vitamin D from different sources (UV, food, drugs) should not exceed 4000 IU per day. 1 IU of vitamin D = 0.025 mcg.

Drugs that replenish the amount of vitamin D in the body:

Ergocalciferol (synonym: Calciferol) - vitamin D2 is produced in the form of:

Dragee ergocalciferol,
A solution of ergocalciferol in oil,
Fish fat,
Dihydrotachysterol (solution).

Cholecalciferol - Vitamin D3 is available as:

Videhol (solution in oil),
Aquadetrim (drops),
Vigantol (oil solution),
Calcium D3-Nycomed (chewable tablets),
Fosavance (tablets),
Calcitriol, Alfacalcidol (capsules),
Alpha-D3-TEVA (capsules).

Vitamin D is insoluble in water, but soluble in fats, so its intake must be accompanied by a certain amount of fat-containing food. Vitamin D is well absorbed in the presence of vitamin E, vitamin A , group B.

Since vitamin D tends to be deposited in excess of it in the body, its overdose causes intoxication, which is reflected in the following symptoms: