Provitamins examples. What vitamins are meant under the general designation "vitamin A"? Exceptions to use

Vitamins– these are organic compounds that are directly involved in the metabolic processes of the body. Coming mainly with food, these substances become components of the active centers of catalysts. But what does this mean?! Everything is extremely simple! Any reaction that occurs inside the human body, whether it is the digestion of food or the transmission nerve impulses in neurons, occurs with the help of special enzyme proteins, which are also called catalysts. Thus, due to the fact that vitamins are part of enzyme proteins, their presence in them makes possible process metabolism (these are the chemical reactions that occur in the body and serve the purpose of maintaining life in it).

In general, vitamins are substances of the most diverse nature of origin, which are necessary for the full development and functioning of the human body, because by their essence and the tasks they perform, they are activators of many life processes.

As for the history of vitamin research, it dates back to the end of the nineteenth century. For example, the Russian scientist Lunin studied the influence mineral salts on the condition of laboratory mice. In the study, one group of mice was fed a diet of components milk (casein, fats, salt and sugar were introduced into their diet), while another group of mice received natural milk. As a result, in the first case the animals were significantly exhausted and died, while in the second case the condition of the rodents was quite satisfactory. Thus, the scientist came to the conclusion that there are also certain substances in the products that are necessary for the normal functioning of a living organism.

However, it is worth noting that the scientific community did not take Lunin’s discovery seriously. But in 1889, his theory was confirmed. Dutch doctor Eijkman, examining mysterious illness Beriberi found out that it can be stopped by replacing refined grains in the diet with “coarse” unrefined ones. Thus, it was found that the husk contains a certain substance, the consumption of which causes the mysterious illness to recede. This substance is vitamin B1.

In subsequent years, in the first half of the 20th century, all other vitamins known to us today were discovered.

The concept of “vitamins” was first used in 1912 by the Polish scientist Casimir Funk, who, with the help of his research, was able to extract substances from plant foods that helped experimental pigeons recover from polyneuritis. IN modern classification these substances are known as thiamine (B6) and niacin (B3). He was the first to propose calling all substances from this area the word “Vitamins” (Latin: Vita - life and Amines - the name of the group to which vitamins belong). It was these scientists who first introduced the concept of vitamin deficiency, and also the doctrine of ways to cure it.

We all know that the names of vitamins, as a rule, consist of a single letter of the Latin alphabet. This trend makes sense in the sense that the vitamins were discovered in this order, that is, they were given names according to alternating letters.

Types of vitamins

Types of vitamins are most often isolated only according to their solubility. Therefore, the following varieties can be distinguished:

Fat-soluble vitamins - this group can be absorbed by the body only when taken along with fats, which must be present in human food. This group includes vitamins such as A, D, E, K.
Water-soluble vitamins - these vitamins, as the name implies, can be dissolved with ordinary water, which means that there are no special conditions for their absorption, because there is a lot of water in the human body. These substances are also called enzyme vitamins because they constantly accompany enzymes (enzymes) and contribute to their full action. This group includes vitamins such as B1, B2, B6, B12, C, PP, folic acid, pantothenic acid, biotin.

These are the main vitamins that exist in nature and are necessary for the full functioning of a living organism.

Sources – which foods contain them?

Vitamins are found in many foods that we are used to eating as food. But at the same time, vitamins are actually a mystery to scientists, because some of them the human body can produce independently, while others under no circumstances can be formed independently and enter the body from the outside. In addition, there are varieties that can only be fully digested under certain conditions, and the reason for this is still not clear.

You can see the main sources of vitamins from food in the table below.

Table 1 - List of vitamins and their sources

Vitamin name	Natural springs
	The main sources are the liver of various animals, whole milk dairy products, and egg yolks. Its predecessor, provitamin A, can be obtained from foods such as carrots, parsley, carrots, apricots, melons and other rich orange and red foods.
Vitamin D (calciferol)	The peculiarity of the absorption of this vitamin is that its full effect is possible only if there is a sufficient amount of calcium and phosphorus in the body. Moreover, vitamin D is precisely the vitamin that the body is able to produce independently under the influence of sun rays getting on the surface of the skin. In addition, you can additionally get it using products such as vegetable oil, eggs, fish.
Vitamin E (tocopherol)	Almost all vegetable oils can be a source of this vitamin; in addition, almonds and peanuts are rich in it.
Vitamin K	Poultry, particularly chicken, sauerkraut, spinach and cauliflower.
Vitamin B1 (thiamine)	Products such as all legumes, pork, hazelnuts, and any herbal products coarse. In addition, dry brewer's yeast is a valuable source of this vitamin.
Vitamin B2 (riboflavin)	The presence of this vitamin is especially rich here. chicken liver and various dairy products.
	All vegetables that are green, chicken, nuts, meat by-products.
	One of the most common vitamins because it is found in many foods of both plant and animal origin. And rice, offal, and yeast are especially rich in its content.
Vitamin B6 (pyridoxine)	Sprouted wheat, bran, cabbage and many other products that are consumed raw.
	Green leafy vegetables, nuts, bananas, eggs.
Vitamin B12 (cyanocobalamin)	Seafood in particular seaweed and caviar various types fish, cottage cheese, yeast and offal.
	Citrus fruits, bird cherry, currants, many fruits, cabbage of any kind and green vegetables.
Vitamin H (biotin)	Legumes, in particular soybeans and soy products, bananas, egg yolk, dairy products and liver.

In addition to natural sources of vitamins, they are now very popular vitamin complexes, which can be purchased. They exist great amount varieties, the composition and concentration of vitamins in them are different, because each is designed to solve a particular problem. So you can find vitamins for adults, for men, for pregnant women. They are formed on the basis of which vitamins are consumed more than others in this case and which reserves need to be replenished. Vitamin complexes in capsules have an undeniable advantage over natural ones - they are composed in such proportions in which they will have the maximum effect on the body; you can create a diet of the same usefulness from natural products very difficult, and sometimes requires in-depth knowledge of biology and chemistry.

But many scientists believe that the usefulness synthetic drugs much lower than natural ones due to worse digestibility. Others, on the contrary, call vitamin ampoules a panacea and a solution to problems in modern world, in which it is difficult to find harmless and environmentally friendly clean products. Which opinion is considered correct is still unknown.

The role of vitamins in the human body; their benefits; consequences of shortage

The importance of the effect of vitamins on the human body and their benefits is perfectly illustrated by the fact that there is not a single vital system, not a single ongoing process that could function without the influence of vitamins.

Not having or not getting enough vitamins can have undesirable health consequences. There is even a concept of vitamin deficiency, which is the name given to a state of insufficient necessary substances, manifested by various symptoms.

Table 2 - List of vitamins, their functions and consequences of deficiency

Vitamin name	Functions performed	Consequences of lack
Vitamin A (retinol, betacarotene)	Very important vitamin for the organs of vision, in addition, it forms the immune system and affects the condition and growth of hair and nails, can promote elasticity skin.	The most striking manifestation of a lack of this vitamin is manifested in “night blindness,” which consists of a deterioration in the ability to see in the dark and twilight. Moreover, in bad situations is fraught with complete loss of vision. In children, the deficiency manifests itself in slow physical and mental development. In addition, a small amount of vitamin A in the body worsens the condition of hair, nails and skin.
Vitamin D (calciferol)	Forms the human bone structure, promotes the healthy development of teeth and bones. In addition, it regulates cell activity.	Problems and fragility skeletal system, rickets in children. In addition, it can provoke excessive nervous excitability.
Vitamin E (tocopherol)	Acts in the body as an antioxidant, protecting cell membranes from free radicals. Helps normal blood circulation, and also participates in the formation of muscles.	Disturbances in the structure of muscle tissue and weak immunity. In addition, a lack of vitamin can provoke the formation of tumors.
Vitamin K	Its effect on the body is that it promotes normal blood clotting.	Hemorrhagic syndrome can be a consequence of a lack of this vitamin, in which blood clotting worsens and there is a danger of bleeding, both external and internal.
Vitamin B1 (thiamine)	Helps extract energy from carbohydrates obtained. Improves appetite and shapes normal development nervous system.	A lack of vitamin B1 can lead to serious problems with the cardiovascular system.
Vitamin B2 (riboflavin)	A very important “detail” in metabolism; in addition, it is involved in correct composition all mucous membranes of the body.	Such consequences as the appearance of cracks in the skin, general deterioration of the condition of the skin, anemia, insomnia and dizziness.
Vitamin B3, PP (nicotinic acid)	It affects cholesterol levels in the body, organizes proper metabolism, and is also considered a vitamin for memory.	When there is a shortage general weakness, bad feeling and disorders in the nervous system.
Vitamin B5 (pantothenic acid)	Promotes good fat and protein metabolism.	Due to the fact that this vitamin is so common and found in many foods, deficiency is very rare. Mainly affects disorders of the adrenal glands.
Vitamin B6 (pyridoxine)	Very important for metabolism, blood circulation and amino acid metabolism.	Mainly affects the functioning of the nervous system and can cause weakness, depression and anemia.
Vitamin B9 (folic acid)	It mainly affects the correct transfer of genetic information from mother to fetus, and also affects the level of hemoglobin in the blood.	Shortage leads to abnormal development fetus during pregnancy.
Vitamin B12 (cyanocobalamin)	Participates in the formation of blood and the “correct” level of iron in the blood. In addition, it ensures metabolism at the cellular level.	Severe cases of anemia and hair loss.
Vitamin C (ascorbic acid)	Very strongly affects the formation of collagen, which is responsible for elasticity and protective functions skin. In addition, it is responsible for strong immunity and protects the heart from overload.	The most important disease that occurs with a long-term lack of vitamin C is scurvy, in which the gums bleed, the immune system is weakened and the person quickly gets tired.
Vitamin H (biotin)	Mainly involved in proper metabolism.	Metabolic dysfunctions and digestibility of various nutritional components.

Daily norm

It is necessary to maintain the daily intake of vitamins in order to maintain the normal functioning of all body systems. There should be neither a deficiency of these substances nor an excess of them. Both cases can lead to very unpleasant consequences.

Approximate daily intake of vitamins for different people age groups We present in the table what follows.

Table 3 - Daily intake of vitamins for different age categories

Vitamin name	Necessary daily norm
Vitamin name	Newborns and children up to one year old	Children from 1 to 10 years old	Adult men and women	Aged people
Vitamin A (retinol, betacarotene)	400 mcg	500-700 mcg	3400-5000 IU	3600-6000 IU
Vitamin D (calciferol)	10 mcg	2.5-4 mcg	100-500 IU	150-300 IU
Vitamin E (tocopherol)	3-4 mcg	5-7 mcg	25-40 IU	45-60 IU
Vitamin K (phylloquinone)	5-10 mcg	15-30 mcg	50-200 mcg	70-300 mcg
Vitamin B1 (thiamine)	0.3-0.5 mg	0.7-1 mg	1.1-2.5 mg	1.5-3 mg
Vitamin B2 (riboflavin)	0.3-0.5 mg	0.7-1.2 mg	1.3-3 mg	2-3.5 mg
Vitamin B3, PP (nicotinic acid)	5-6 mg	9-12 mg	12-25 mg	15-27 mg
Vitamin B5 (pantothenic acid)	2-3 mg	3-5 mg	5-12 mg	7-15 mg
Vitamin B6 (pyridoxine)	0.3-0.6 mg	1-1.2 mg	1.6-2.8 mg	up to 20 mg
Vitamin B9 (folic acid)	not installed	not installed	160-400 mcg	200-500 mcg
Vitamin B12 (cyanocobalamin)	0.3-0.5 mcg	0.7-1.4 mcg	2-3 mcg	2.5-4 mcg
Vitamin C (ascorbic acid)	25-35 mg	40-45 mg	45-100 mg	55-150 mg
Vitamin H (biotin)	10-15 mcg	20-30 mcg	35-200 mcg	up to 300 mcg

*IU stands for international unit. In pharmacology, it is a measure for substances such as vitamins, hormones, medications and so on. ME is based on the biological activity of each specific substance. Thus, IU does not have a standardized size and it can be different for each specific substance.

Negative effects of vitamins; their possible harm

The negative effects of vitamins can occur when our body receives an excessive dose of one or more vitamins.

It should be noted that when obtaining vitamins from food, it is extremely difficult to get hypervitaminosis - an excess of vitamins, because there they are in small quantities and, thanks to their natural structure, are very easily and well absorbed and processed by the body.

The situation is much more complicated with synthetic vitamins, which are freely available. Because very often in this way, without taking into account the recommended doses of vitamins, people consume them in very large quantities, believing that in this way they bring themselves much more benefit. But each vitamin can either positively affect any process in the body or cause irreparable harm.

So, an excess of vitamin C can make blood vessels very fragile. Vitamin D in large quantities will cause your blood pressure to jump and lead to loss of consciousness. And a lot of vitamin A, according to most scientists, can even provoke the occurrence of tumors.

Thus, it should be remembered that only common sense, moderation and correct knowledge about the nature of vitamins and correct dosage can give you much more benefit than an inordinate desire to get as much as possible from them. And of course, pay attention to products with high content essential vitamins precisely because of their seasonality, because tomatoes in winter will not give you any benefit. Therefore, build your diet correctly, focusing on fresh food, and in winter on synthetic vitamins in the correct dosage.

Vitamin A belongs to the group of fat-soluble compounds (lipovitamins). It is able to be deposited in the body, mainly in the liver.

According to WHO, with vitamin A deficiency, none of the food products can cover its deficiency, and therefore it is necessary to take retinol in the form of pharmacological preparations.

Vitamin A is formed in the body from provitamins – “carotenoids” – supplied from outside. The term comes from carrot (English), since these precursor substances were first discovered in carrots. Related compounds are present in a wide range of vegetables and fruits (especially yellow, red and orange), as well as in algae and certain types mushrooms

Currently, science knows more than half a thousand carotenoids.

The most common ones are:

a-, b- and d-carotene;
zeaxanthin;
lutein;
lycopene

Beta-carotene undergoes oxidation in the human liver and, when broken down, forms vitamin A.

The unit of measurement for retinol is 1 ER, which corresponds to 1 mcg of retinol, 6 mcg of b-carotene, or 12 mcg of other carotenoids.

1 mcg is 3.33 IU for retinol or 10 IU for b-carotene.

Important:It has been experimentally proven that beef, skim milk, and grain crops do not contain sufficient quantity carotene and retinol, i.e. they cannot serve as complete sources of vitamin A.

Animal products containing vitamin A:

beef liver;
Cod liver;
fish fat;
caviar sea fish;
whole milk;
cream;
egg yolk.

Plant sources:

carrot;
tomatoes;
pepper ("Bulgarian" and hot cayenne);
spinach;
broccoli;
parsley;
parsley;
peas;
soya beans;
apples;
(kelp algae).

Important:Provitamin A is present in large quantities in herbs such as alfalfa, horsetail, peppercorn, lemongrass, nettle, sage, hops, plantain, etc.

Vitamin A is involved in a number of metabolic processes occurring in human body. It plays an important role in the regulation of protein biosynthesis and ensures the stability of cell membranes. Connection is necessary for formation bone tissue, as well as enamel and dentin. Thanks to him, they are formed necessary for a person fat reserves.

Note:It has been known since ancient times that consuming liver improves visual acuity and helps prevent or cure night blindness.

Retinol is necessary for adequate photoreception (light perception); it takes part in the biosynthesis of retinal pigment. The most important carotenoids prevent cataracts and significantly reduce the likelihood of developing degeneration " macular spot" - pathology, which is one of the main causes of blindness.

Vitamin A is one of the most effective natural antioxidants. It minimizes the harmful effects of free radicals, which allows the use of retinol and carotenoids for prevention and treatment (in complex therapy) oncological diseases. During clinical trials b-carotene has been shown to reduce the likelihood of relapses malignant neoplasms after surgery.

The antioxidant effect helps prevent the development of a number of serious pathologies heart and blood vessels.

Vitamin A can increase serum concentrations necessary for the body high density lipoproteins.

The carotenoid lycopene, which is found in large quantities in tomatoes, prevents the deposition of cholesterol on vascular walls, thus protecting a person from and his dangerous consequences. This provitamin also reduces the likelihood of developing malignant breast and prostate cancer.

The condition of the nonspecific condition largely depends on vitamin A. The compound is capable of increasing the body's resistance to infectious agents of bacterial and viral nature(phagocytic activity of leukocytes increases significantly).

A sufficient intake of vitamin A from food reduces the likelihood of developing colds, as well as genitourinary and respiratory systems and organs gastrointestinal tract.

Children who eat well and regularly receive retinol and carotenoids in the required amount are much easier to tolerate "" and ".

Constant presence in serum is sufficient high level retinol significantly increases the life expectancy of patients suffering.

Vitamin A is actively involved in the process of regeneration of the epithelial layer of the skin and mucous membranes. Its drugs are widely used in the treatment of any (, etc.), as well as skin damage due to mechanical injuries or burns. By stimulating the process of collagen biosynthesis, retinol ensures rapid healing, greatly reducing the risk of developing secondary infectious complications. Vitamin A significantly improves the quality of tissue that is formed again at the site of significant damage.

Note:included in many modern cosmetic preparations included are retinoid substances, which are nothing more than synthetically produced analogues of vitamin A. Creams with retinoids are very good for sunburn.

The beneficial effect of retinol on epithelial cells provides improvement functional activity bronchi and lungs. Providing patients with vitamin A supplements can speed up recovery from such organ pathologies digestive tract, How peptic ulcer and colitis (inflammation of the mucous membranes of the walls of the large intestine).

Retinol is one of the most important organic compounds, necessary for normal intrauterine development future child.

Women who are preparing to become mothers are advised to consume adequate amounts of vitamin A to improve fetal nutrition and reduce the likelihood of having an underweight baby.

For pregnant women, the daily intake of retinol should be 750-770 mcg. Recommended for nursing mothers Russian doctors the norm is more - 1200-1300 mcg.

Important: During pregnancy, you should not consume more than 6000 IU per day, since high doses have a teratogenic effect on the fetus. For the same reason, fish oil is strictly contraindicated for women during pregnancy.

How much vitamin A is needed per day?

The average vitamin A intake for an adult is 3300 IU (1000 mcg) per day. Against the background of pathologies caused by hypovitaminosis A, it is recommended to increase consumption by 3 times (up to 10,000 IU).

Important: climatic conditions may affect the body's need for vitamin A. Cold weather does not have any effect on retinol metabolism, but hot climate makes its own adjustments: the need for this vitamin increases significantly.

Babies in their first year of life require 400 mcg of retinol per day. Children from 1 to 3 years old need 450 mcg of the vitamin, from 4 to 6 years old - 500 mcg, and from 7 to 10 years old - 700 mcg per day.

For teenagers, the norms are the same as for adults.

Note:The need is reduced in women who take birth control pills.

Hypovitaminosis: causes and symptoms

The level of vitamin A in plasma is considered insufficient if it is below 0.35 µmol/l.

Even at a level of 0.70-1.22 µmol/l, the amount of retinol in its main “storage”, i.e. in the liver, is noticeably reduced.

The main reasons for the development of hypovitaminosis include:

To fully absorb vitamin A, you need to consume enough fat and complete protein. It must be present in food, the absence of which makes it difficult to absorb retinol.

Important:Hypovitaminosis A is quite often observed in vegetarians who do not replace animal products with the required amount of complete plant protein.

Typical manifestations of hypovitaminosis include:

increased temperature sensitivity;
decreased pain threshold;
early aging of the skin (appearance of wrinkles);
dryness and flaking of the skin;
redness of the eyelids;
feeling " foreign body"or "sand" in the eyes;
accumulation of mucus and formation of crusts in the corners of the eyes;
urinary incontinence (sphincter weakness);
hyperesthesia (pathologically high degree of sensitivity) of tooth enamel;
deterioration of erectile function;
early ejaculation.

A very characteristic manifestation of retinol deficiency is hemeralopia - a significant deterioration of vision at dusk.

Consequences of vitamin A deficiency:

xerophthalmia (dry cornea);
corneal clouding;
precancerous pathologies and skin cancer;
atrophic gastritis;
intestinal inflammation;
pancreatitis;
decreased sex drive;
mastopathy;
malignant tumors of the mammary glands;
gynecological diseases (etc.);
cachexia (exhaustion);
anemia (anemia);
frequent respiratory infections;
cystic liver formations;
insomnia.

Indications for taking vitamin A

Vitamin A is prescribed orally for injection(v/m) or for local application if diagnosed:

pathologies of the skin and mucous membranes;
inflammation of the cornea and conjunctiva of the eyes;
burns, fractures and other injuries (to speed up regeneration).

Mild and moderate hypovitaminosis requires doses of up to 33,000 IU for adult patients and from 1,000 to 5,000 for children. At skin diseases dosages are higher - 50000-100000 and 5000-10000 IU, respectively.

Hypervitaminosis

Important:vitamin A provides toxic effect per body when consuming 25,000 IU per day.

Symptoms of hypervitaminosis:

pain in the abdominal area;
hepatosplenomegaly;
alopecia;
arthralgia;
“jams” in the corners of the mouth;
delay of menstruation;
dry skin;
increased fragility and thickening of the nail plates.

Important:A lack of zinc leads to impaired absorption of retinol.

The combination of vitamin A and ethanol causes more liver damage than exposure to alcohol.

Description

Retinol is fat soluble, so it requires fats to be absorbed by the digestive tract, as well as minerals. Its reserves remain in the body long enough that it does not need to be replenished every day. There are two forms of this vitamin: this is ready-made vitamin A (retinol) and provitamin A (carotene), which is converted into vitamin A in the human body, so it can be considered plant form Vitamin A. Vitamin A is pale yellow in color and is produced from the red plant pigment beta-carotene.

Compounds similar in structure:

retinol (vitamin A alcohol, vitamin A 1, axerophthol);
dehydroretinol (vitamin A 2);
retinal (retinene, vitamin A-aldehyde);
retinolic acid (vitamin A-acid);
esters of these substances and their spatial isomers.

Sources

Vegetables (carotene)	Animals	Synthesis in the body
Green and yellow vegetables (carrots, pumpkin, bell peppers, spinach, broccoli, green onions, parsley), legumes (soybeans, peas), peaches, apricots, apples, grapes, watermelon, melon, rose hips, sea buckthorn, cherries; herbs (alfalfa, borage leaves, burdock root, cayenne pepper, fennel, hops, horsetail, kelp, lemongrass, mullein, nettle, oats, parsley, peppermint, plantain, raspberry leaves, clover, rose hips, sage, bearberry, violet leaves , sorrel).	Fish oil, liver (especially beef), caviar, milk, butter, margarine, sour cream, cottage cheese, cheese, egg yolk	Formed as a result of the oxidative breakdown of β-carotene

The best sources of vitamin A are fish oil and liver, followed by butter, egg yolks, cream and whole milk. Cereal products and skim milk, even with vitamin supplements, are unsatisfactory sources, as is beef, which contains trace amounts of vitamin A.

Functions

Vitamin A is involved in redox processes, regulation of protein synthesis, promotes normal metabolism, the function of cellular and subcellular membranes, plays an important role in the formation of bones and teeth, as well as fat deposits; necessary for the growth of new cells, slows down the aging process.

Vitamin A supports night vision by producing a pigment called rhodopsin, which can detect minimal light, which is very important for night vision. It also helps to moisturize the eyes, especially the corners, protecting them from drying out and subsequent injury to the retina.

Vitamin A is essential for the normal functioning of the immune system and is an integral part of the process of fighting infection. The use of retinol increases the barrier function of mucous membranes, increases the phagocytic activity of leukocytes and other factors of nonspecific immunity. Vitamin A protects against colds, flu and infections respiratory tract, digestive tract, urinary tract. The presence of vitamin A in the blood is one of the main factors responsible for the fact that children in more developed countries tolerate such diseases much more easily. infectious diseases like measles, chickenpox, whereas in countries with low level life is much higher mortality from these “harmless” viral infections. Providing vitamin A prolongs the life of even AIDS patients.

Retinol is necessary for the maintenance and restoration of epithelial tissues that make up the skin and mucous membranes. It’s not for nothing that in almost all modern cosmetics contains retinoids - its synthetic analogues. Indeed, vitamin A is used in the treatment of almost all skin diseases (acne, pimples, psoriasis, etc.). In case of skin damage (wounds, sunburn) Vitamin A accelerates the healing process, and also stimulates collagen synthesis, improves the quality of newly formed tissue and reduces the risk of infections.

Due to its close connection with the mucous membranes and epithelial cells Vitamin A has a beneficial effect on the functioning of the lungs, and is also a worthwhile addition in the treatment of certain diseases of the gastrointestinal tract (ulcers, colitis).

Retinol is necessary for normal embryonic development, nutrition of the fetus and reducing the risk of pregnancy complications such as low birth weight of the newborn.

Vitamin A takes part in the synthesis steroid hormones(including progesterone), spermatogenesis, is an antagonist of thyroxine - the thyroid hormone.

Both vitamin A and β-carotene, being powerful antioxidants, are means of prevention and treatment cancer diseases, in particular, preventing the reappearance of the tumor after surgery.

Both vitamin A and β-carotene protect brain cell membranes from destructive action free radicals, while b-carotene neutralizes the most dangerous species free radicals: radicals polyunsaturated acids and oxygen radicals.

The antioxidant effect of β-carotene plays an important role in the prevention of heart and artery diseases, it has protective effect in patients with angina pectoris, and also increases the level of “good” cholesterol (HDL) in the blood.

Lutein and zeaxentin are the main carotenoids that protect our eyes: they help prevent cataracts and also reduce the risk of macular degeneration ( the most important body vision), which in every third case is the cause of blindness. With vitamin A deficiency, keratomalacia develops.

Another carotenoid, lycopene (found mainly in tomatoes), protects against atherosclerosis by preventing the oxidation and accumulation of low-density cholesterol on the walls of arteries. In addition, it is the most powerful carotenoid in terms of protection against cancer, especially breast, endometrial and prostate cancer.

Daily requirement

900 mcg (3000) for adults (for pregnant women 100 mcg more, for nursing mothers - 400 mcg more);
400-1000 mcg for children, depending on age and gender;
For diseases associated with retinol deficiency, the dosage can be increased to the upper permissible level consumption - 3000 mcg.

The above dosages apply exclusively to the retinoid form of vitamin A. The carotenoid form is not as toxic.

Interactions

Vitamin E (tocopherol) protects vitamin A from oxidation both in the intestines and in tissues. Therefore, if you are deficient in vitamin E, you cannot absorb the required amount of vitamin A and therefore the two vitamins must be taken together.
Zinc deficiency can impair the conversion of vitamin A into its active form. Because your body, without sufficient zinc, cannot synthesize vitamin A-binding protein—the transport molecule that transports vitamin A through the intestinal wall and releases it into the blood—zinc deficiency can result in poor supply of vitamin A to tissues. These two components are interdependent: thus, vitamin A promotes the absorption of zinc, and zinc also acts in relation to vitamin A.
Mineral oil, which can sometimes be taken as a laxative, can dissolve fat-soluble substances (such as vitamin A and beta-carotene). These vitamins then pass through the intestines without being absorbed because they are dissolved in mineral oil, from which the body cannot extract them. Permanent use mineral oil can thus lead to vitamin A deficiency.
For normal absorption of vitamin A, the presence of fats and proteins in the diet is necessary. The difference between edible oil and mineral oil is that the body can absorb edible fat along with the vitamin A dissolved in it; The body does not absorb mineral oil.

Notes

Vitamins
Fat-soluble vitamins	Vitamin A(Retinol) Vitamin D (Ergocalciferol D 2, Cholecalciferol D 3) Vitamin E (Tocopherol) Vitamin F Vitamin K Ubiquinone (Q)
Water-soluble vitamins Group B	Thiamine (B 1) Riboflavin (B 2) Nicotinic acid (PP, B 3) Choline (B 4) Pantothenic acid (B 5) Pyridoxine (B 6) Biotin (B 7) Folic acid (B 9) Cyanocobalamin (B 12) Inositol (B 8)
Other water-soluble vitamins:	Ascorbic acid (C) S-methylmethionine (U)

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Vitamin A (retinol and other retinoids) and provitamin A (β-carotene and other carotenoids) affect almost all organs and systems of the body and play a critical role for its normal functioning.

Description of Vitamin A:
Vitamin A is a group of fat-soluble substances similar in composition (retinol and other retinoids) that enter the human body with products of animal origin. Vitamin A can also be synthesized directly in the human body from provitamin A supplied with plant foods. Vitamin A does not dissolve in water, and in order for it to be absorbed and benefit the body, a fatty environment is required. When cooking foods, up to 50% of this vitamin is lost. Both deficiency and excess of vitamin A in the human body can cause serious diseases.

Why does the body need vitamin A?

Vitamin A is very important for proper operation immune system, protects the body from many viruses and infections.
Vitamin A is also important for of cardio-vascular system, it prevents bad cholesterol from accumulating.
Helps the endocrine system function normally.
The condition of a person’s skin depends on the amount of this vitamin. Sufficient intake of vitamin A in the body helps restore all layers damaged tissue and cope with a variety of skin problems such as eczema, psoriasis, acne, burns, wounds and so on. This is why some people call vitamin A the “skin” vitamin.
Vitamin A is very important for vision. It affects the condition of the retina, the perception of light by photoreceptors, as well as color perception.
Vitamin A helps regulate metabolic processes and synthesis of protein compounds in the body.
Participates in the formation and growth of new cells and affects tissue respiration.
Vitamin A has antioxidant properties and helps slow down the aging process in the body, preventing the occurrence and development of cancer.
During pregnancy, vitamin A is necessary not only for the woman, but also for the developing fetus for its normal nutrition and development.
This vitamin is very important for normal physical and mental development children and adolescents, since it is involved in almost all basic functions of the body.

Interaction of vitamin A with other substances:
In order for vitamin A to be well absorbed, the body must have a sufficient amount of vitamin B, as well as phosphorus.
As mentioned above, a fatty environment is necessary for the absorption of vitamin A, therefore, when consuming foods containing carotenoids (provitamin A), it is necessary to add vegetable oil or sour cream.
Alcohol and some medications interfere with the absorption of vitamin A.

The body's daily requirement for vitamin A:
The daily requirement for vitamin A depends on gender, age, physical and mental stress, weight, and even climate and time of year.
The daily requirement for this vitamin in men is about 1000 mcg, in women – about 800 mcg, in children and adolescents – 300-700 mcg, depending on age and weight. The need for vitamin A increases during breastfeeding, during illness, during hot periods, and during heavy physical exertion.

Products containing vitamin A:
Vitamin A is found in animal products, and provitamin A is found in foods plant origin and dairy products. At the same time, experts recommend that 1/3 of vitamin A enter the human body with animal products, and 2/3 in the form of provitamin A with products of plant origin.

Sources of vitamin A (retinol and other retinoids):
- (V beef liver vitamin A is much more than in pork);
— Butter;
— Sour cream, cottage cheese and others;
- Egg yolk;
— Liver of sea fish;
- and other products.

Sources of provitamin A (β-carotene and other carotenoids):
— (fresh and dried apricots);
— ;
- And ;
— ;
— ;
— ;
- and other products.

Lack of vitamin A in the body:
A lack of vitamin A in the body primarily affects vision. The more acute and prolonged the deficiency of this vitamin, the more serious the consequences for the eyes. With a lack of vitamin A, dry skin and mucous membranes may occur, frequent colds, violation menstrual cycle in women, destruction of bone tissue (especially teeth), brittle hair and nails, infertility in men, mental disorders, diseases of the digestive, endocrine, genitourinary and other body systems. And this is far from full list possible consequences.
Vitamin A deficiency can be replenished with vitamin-containing medications, but this is done only as prescribed by a doctor.

Excess vitamin A in the body:
An excess of vitamin A in the body is no less dangerous than its deficiency. An excess of this vitamin can also cause problems with skin, hair and nails. Joint pain, illness internal organs, enlarged liver and spleen and other problems in the body can be caused by an excess of vitamin A. It should be noted that food extremely rarely causes an excess of vitamin A in the body, especially if a person is balanced. As a rule, taking medications to replenish vitamin A is most often the cause of an excess of this vitamin. Taking such drugs is not permissible without consulting a doctor.

TAKE CARE OF YOURSELF AND BE HEALTHY!

Vitamin A receives little attention in the media, and as a result, people are often unaware of how much they consume and how much they need to stay healthy. This is despite mounting evidence that suggests vitamin A plays significant role in reducing the risk of many modern diseases. What exactly is vitamin A? This article will tell you about vitamin A, how it works in the body and what foods are rich in it.

Vitamin A belongs to a group of similarly structured fat-soluble compounds that include retinol, retinoic acid, and also include carotenoids such as beta-carotene.

It is these carotenes that are responsible for the color of many vegetables, such as carrots and peppers. Carotene is not vitamin A, in fact it is a provitamin, which means that only after entering the body, carotene is converted into a vitamin, which the body then processes and uses for its own purposes.

This conversion is not very efficient and occurs at approximately a 2:1 ratio. Retinol is true vitamin A, its structure allows it to be fat soluble. Unlike many vitamins, vitamin A is toxic in large doses, meaning its content in supplements must be controlled.

When consuming foods containing provitamin A, get toxic doses almost impossible.

How does vitamin A work in the body?

The benefits of vitamin A for the retina are very well known, and the ability of the eyes to see at night also depends on it. Retinol is converted to retinal, a pigment that is a light-sensitive molecule found on the retina.

Light comes into contact with the retina, causing a chain chemical reaction, which is ultimately interpreted in our brain by such a function of our body as vision. A slight deficiency of vitamin A is known to reduce the ability to see in the dark, and ultimately lead to night blindness.

Vitamin A plays a very important role in the immune system; this vitamin is necessary for the body to produce cells for the innate and adaptive immune systems. These immune cells necessary to destroy pathogens and infections that would otherwise damage cells.

Vitamin A deficiency is strongly associated with increased risk development of modern diseases such as cardiovascular diseases and cancer. It is not yet known exactly how vitamin A helps the body reduce damage caused by pathogenic microorganisms, and prevent the development of cancer cells.

Vitamin A is necessary for the transcription of a number of genes, which is very important for the healthy functioning of all cells in the body. The effect of vitamin A is special meaning for the skin, it converts immature skin cells into mature ones.

The skin has greater resistance when pathogenic microbes come into direct contact with the skin. When the skin is injured, it increases its ability to heal. IN reproductive function this vitamin also plays a significant role, its participation in embryonic development simply necessary.

Vitamin A, which foods contain it?

Vitamin A differs from other vitamins in that it can be found in foods of plant and animal origin. Beta-carotene, for example, is found in large quantities in carrots and peppers. Once in the body, it is converted into retinol before the body can use this vitamin. This conversion is not a very effective source for sufficient supply of the vitamin to our body.

Animal sources of vitamin A (fatty fish, liver, egg yolk) contain retinol, which is biologically active form, that is, animal products are more valuable than plant products.

There are many signs by which you can understand that the body does not have enough vitamin A, these include: poor wound healing, decreased vision, dandruff, rash-affected skin, premature appearance of wrinkles, pain, weight loss, loss of appetite.

There are also known signs of vitamin A excess: sluggish general state, menstrual irregularities, nausea, gait disturbance, painful sensations in the bones.

Conclusions about the benefits of vitamin A

Despite the lack of mention of vitamin A in products mass media, compared to vitamins such as C or D, it is also important for maintaining healthy body.

Vitamin A is involved in a number of biological functions, and vitamin deficiency is associated with an increased risk of cancer and cardiovascular diseases. Especially important it has benefits for the immune system, skin health and good vision.

Food sources vitamins can be fatty fish, organ meats such as liver, brightly colored vegetables (carrots, peppers, pumpkin).

Vitamin A - video

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