Provitamin examples. What vitamins are referred to 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. Acting 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 takes place inside the human body, whether it is the digestion of food or the transmission nerve impulses on neurons, occurs with the help of special proteins-enzymes, which are also called catalysts. Thus, due to the fact that vitamins are part of protein enzymes, they, by their presence in them, make possible process metabolism (these are the chemical reactions that take place 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, in their essence and tasks performed, they are activators of many life processes.

As for the history of vitamin research, it dates back to the late nineteenth century. For example, the Russian scientist Lunin studied the influence mineral salts on the condition of laboratory mice. During the study, one group of mice were fed a diet of constituent parts 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 emaciated 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 still some 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 nevertheless confirmed. Dutch doctor Eikman, examining mysterious disease beriberi found that replacing refined grains with “coarse” unrefined grains in the diet can stop it. Thus, it was found that the husk contains a certain substance, the consumption of which causes the mysterious ailment 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.

For the first time, the concept of "vitamins" was used in 1912 by the Polish scientist Kazimir Funk, who, with the help of his research, managed to extract substances from plant foods, they helped experimental pigeons recover from polyneuritis. IN modern classification these substances are known as thiamine (B6) and nicotinic acid (B3). For the first time, he proposed to call all substances from this area the word "Vitamins" (lat. Vita - life and Amines - the name of the group to which vitamins belong). It was these scientists who first introduced the concept of beriberi, and he also owns the doctrine of how to cure it.

We all know that the names of vitamins, as a rule, are in a single letter of the Latin alphabet. This trend makes sense in the sense that vitamins were discovered in that 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 together 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 such vitamins 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 - what products contain?

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

You can find the main sources of getting 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, dairy products from whole milk, egg yolks. Its precursor, provitamin A, can be obtained from foods such as carrots, parsley, carrots, apricots, melons, and other rich orange and red foods.
Vitamin D (calciferol)	A feature 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. At the same time, vitamin D is exactly the vitamin that the body is able to produce on its own under the influence of sun rays falling on the surface of the skin. In addition, you can additionally get it with the help of 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 meat, particularly chicken, sauerkraut, spinach, and cauliflower.
Vitamin B1 (thiamine)	They have a fairly large presence in their composition of products such as all legumes, pork, hazelnuts, and any herbal products coarse grinding. In addition, dry brewer's yeast is a valuable source of this vitamin.
Vitamin B2 (riboflavin)	It is especially rich in the presence of this vitamin in chicken liver and various dairy products.
	All vegetables that are green in color, chicken meat, nuts, organ meats.
	One of the most common vitamins, because it is found in many products of both plant and animal origin. And rice, offal, yeast are especially rich in its content.
Vitamin B6 (pyridoxine)	Sprouted wheat, bran, cabbage and many other foods that are eaten raw.
	Green leafy vegetables, nuts, bananas, eggs.
Vitamin B12 (cyanocobalamin)	Marine products in particular sea kale and caviar various kinds 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 are now very popular vitamin complexes that 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. Complexes of vitamins 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, make up 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 due to the worst 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 use; consequences of a shortage

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

The absence or lack of sufficient amounts of vitamins can have undesirable health consequences. There is even the concept of beriberi, the so-called state of insufficient amount essential substances manifested by various symptoms.

Table 2 - List of vitamins, their functions and the 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 the lack of this vitamin is manifested in "night blindness", which consists in the deterioration of the ability to see in the dark and twilight hours of the day. And in bad situations 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 frame, promotes the healthy development of teeth and bones. It also regulates cell activity.	Problems and fragility skeletal system, rickets in children. In addition, it can provoke excessive nervous excitability.
Vitamin E (tocopherol)	Acts as an antioxidant in the body, protecting cell membranes from free radicals. Helps normal blood circulation, in addition, participates in the formation of muscles.	Violations in the structure of muscle tissue and weak immunity. In addition, vitamin deficiency can lead to the formation of tumors.
Vitamin K	Its effect on the body is that it contributes to normal blood clotting.	Hemorrhagic syndrome can be a consequence of a lack of this vitamin, in which blood clotting deteriorates and there is a risk of bleeding, both external and internal.
Vitamin B1 (thiamine)	Helps to extract energy from the received carbohydrates. Improves appetite and forms 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 the metabolism, in addition, it is involved in correct composition all mucous membranes of the body.	Such consequences as the occurrence of cracks in the skin, a general deterioration in the condition of the skin, anemia, insomnia and dizziness.
Vitamin B3, PP (nicotinic acid)	It affects the level of cholesterol in the body, organizes the correct metabolism, and is also considered a vitamin for memory.	When there is a shortage general weakness, bad feeling and disturbances in the nervous system.
Vitamin B5 (pantothenic acid)	Promotes good fat and protein metabolism.	Due to the fact that this vitamin is very common and found in many foods, its deficiency is very rare. It mainly affects disorders in the work of the adrenal glands.
Vitamin B6 (pyridoxine)	It is 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, in addition, it affects the level of hemoglobin in the blood.	Deficiency leads to wrong 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 provides metabolism at the cellular level.	Severe cases of anemia and hair loss.
Vitamin C (ascorbic acid)	It greatly affects the formation of collagen, which is responsible for elasticity and protective functions skin cover. In addition, it is responsible for strong immunity and protects the heart from overload.	The most important disease that occurs with a prolonged 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 disorders and digestibility of various nutritional components.

Daily rate

It is necessary to maintain the daily intake of vitamins in order to maintain the normal functioning of all body systems. There should not be either a deficiency of these substances or their excess. Both cases can lead to very unpleasant consequences.

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

Table 3 - Daily intake of vitamins for different age categories

Vitamin name	Required daily rate
Vitamin name	Newborns and children up to a year	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. IU is based on the biological activity of each specific substance. Thus, IU does not have a standardized size, and for each specific substance it can be different.

Negative effects of vitamins; their possible harm

The negative effects of vitamins can be manifested in cases where our body receives an excessive dose of any 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, due to the 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, not taking into account the recommended doses of vitamins, people use them in a very in large numbers believing that in this way they bring themselves much more benefit. But each vitamin can both positively affect any process in the body, and cause irreparable harm.

So, an excess of vitamin C can make blood vessels very fragile. Vitamin D in large quantities will make your blood pressure jump, leading 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 immoderate desire to get as much as possible from them. And of course, pay attention to products with great content essential vitamins precisely in connection with their seasonality, because tomatoes in winter will not give you any benefit. Therefore, build your diet correctly, focusing in the warm season on fresh food, and in winter 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 the WHO, with hypovitaminosis in vitamin A, none of the food products can cover its deficiency, and therefore the intake of retinol in the form of pharmacological preparations is required.

Vitamin A is formed in the body from provitamins - "carotenoids" coming from outside. The term comes from carrot (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, more than half a thousand carotenoids are known to science.

The most common of these are:

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

Beta-carotene undergoes oxidation in the human liver, and, splitting, forms vitamin A.

The unit of measurement for retinol is 1 ER, which corresponds to 1 µg of retinol, 6 µg of b-carotene, or 12 µg 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, skimmed milk, and cereals contain no enough carotene and retinol, i.e., cannot serve as full-fledged sources of vitamin A.

Animal foods containing vitamin A:

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

Plant Sources:

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

Important:in large quantities, provitamin A is present in herbs such as alfalfa, horsetail, pepper, lemongrass, nettle, sage, hops, and plantain.

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. The connection is necessary for the formation bone tissue as well as enamel and dentin. Thanks to him, they form necessary to a person fat reserves.

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

Retinol is necessary for adequate photoreception (perception of light); it takes part in the biosynthesis of retinal pigment. The most important carotenoids prevent cataracts and significantly reduce the likelihood of degeneration. yellow spot"- a pathology that 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 the prevention and treatment (as part of complex therapy) oncological diseases. During clinical research b-carotene has been shown to reduce the likelihood of relapses malignant neoplasms after the surgical intervention.

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

Vitamin A is able to increase serum concentration 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 the person from and his dangerous consequences. This provitamin also reduces the likelihood of developing malignant and breast cancer, as well as prostate cancer.

The state of non-specific depends largely on vitamin A. The compound is able to increase the body's resistance against infectious agents of bacterial and viral nature(significantly increases the phagocytic activity of leukocytes).

Sufficient intake of vitamin A with food reduces the likelihood of developing colds, as well as infections of the genitourinary and respiratory systems and bodies gastrointestinal tract.

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

Continuous 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 preparations are widely used in the treatment of any (, etc.), as well as skin damage due to mechanical injuries or burns. Due to the stimulation of the collagen biosynthesis process, retinol ensures the fastest healing, greatly reducing the risk of developing secondary infectious complications. Vitamin A significantly improves the quality of tissue that is newly formed at the site of significant damage.

Note:included in many modern cosmetic preparations retinoids are included, which are nothing more than synthetic analogues of vitamin A. Retinoid creams are very good for sunburn.

The beneficial effect of retinol on epithelial cells provides an improvement functional activity bronchi and lungs. Receiving vitamin A preparations for patients can speed up recovery in 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 needed for normal prenatal development future child.

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

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

Important: during childbearing, you can not consume more than 6000 IU per day, because high doses have a teratogenic effect on the fetus. For the same reason, during pregnancy, women are categorically contraindicated in fish oil.

How much vitamin A is required per day?

The average intake of vitamin A 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 has no effect on the metabolism of retinol, but hot climate makes its own adjustments: the need for this vitamin increases significantly.

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

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

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

Hypovitaminosis: causes and symptoms

Plasma vitamin A levels are considered insufficient if they are 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:

For the full assimilation of vitamin A, it is necessary to consume a sufficient amount of fat and complete protein. It must be present in food, the absence of which makes it difficult to absorb retinol.

Important:hypovitaminosis A is often observed in vegetarians who do not replace animal products with the necessary amount of high-grade vegetable protein.

The characteristic manifestations of hypovitaminosis include:

increased temperature sensitivity;
lowering the pain threshold;
early aging of the skin (the appearance of wrinkles);
dryness and peeling of the skin;
redness of the eyelids;
feeling " foreign body"or" sand "in the eyes;
accumulation of mucus and the 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 in vision at dusk.

Consequences of vitamin A deficiency:

xerophthalmia (dryness of the cornea of the eyes);
clouding of the cornea;
precancerous pathologies and skin cancer;
atrophic gastritis;
intestinal inflammation;
pancreatitis;
decrease in sexual desire;
mastopathy;
malignant tumors of the mammary glands;
gynecological diseases (etc.);
cachexia (exhaustion);
anemia (anemia);
frequent respiratory infections;
cystic formations of the liver;
insomnia.

Indications for taking vitamin A

Vitamin A is administered orally, for injection(w / m) or for local application if diagnosed:

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

Mild and moderate hypovitaminosis require doses 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 has toxic effect on the body when consuming 25,000 IU per day.

Symptoms of hypervitaminosis:

pain in the abdominal region;
hepatosplenomegaly;
alopecia;
arthralgia;
"Zaedy" 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 a violation of the absorption of retinol.

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

Description

Retinol is fat soluble, so fats are required for it to be absorbed by the digestive tract, as well as minerals. In the body, its reserves remain long enough not to replenish its reserves every day. There are two forms of this vitamin: it is ready-made vitamin A (retinol) and provitamin A (carotene), which in the human body turns into vitamin A, so it can be considered vegetable form vitamin A. Vitamin A has a pale yellow color, which is formed from the red plant pigment beta-carotene.

Structurally related compounds:

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

Sources

Vegetable (carotene)	Animals	Synthesis in the body
Green and yellow vegetables (carrots, pumpkin, bell peppers, spinach, broccoli, green onion, parsley), legumes (soybeans, peas), peaches, apricots, apples, grapes, watermelon, melon, rose hips, sea buckthorn, cherries; herbs (alfalfa, pins, burdock root, Kayen pepper, fennel, hops, horsetail, kelp, lemon cerebral, nettles, oats, parsley, peppermint, plantain, raspberry leaves, clover, rosehips, sage, braids, leaves of violet, dungeon).	Fish oil, liver (especially beef), caviar, milk, butter, margarine, sour cream, cottage cheese, cheese, egg yolk	Formed as a result of oxidative cleavage 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 negligible amounts of vitamin A.

Functions

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

Vitamin A supports night vision by producing a pigment called rhodopsin that can capture minimal light, which is essential for night vision. It also helps to moisturize the eyes, especially the corners, preventing 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 infection-fighting process. The use of retinol increases the barrier function of the 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. Security with vitamin A prolongs life even for AIDS patients.

Retinol is essential for maintaining and restoring the epithelial tissues that make up the skin and mucous membranes. Not in vain 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.). Skin injuries (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 association with 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.

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

Both vitamin A and β-carotene, being powerful antioxidants, are means of prevention and treatment. cancer, 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 action of β-carotene plays an important role in the prevention of diseases of the heart and arteries, it has protective action in patients with angina pectoris, and also increases the blood levels of "useful" cholesterol (HDL).

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 "strong" carotenoid in terms of protection against cancer, especially breast, endometrial and prostate cancer.

daily requirement

900 mcg (3000) for adults (for pregnant women, more by 100 mcg, for lactating women - by 400 mcg);
400-1000 mcg for children, depending on age and gender;
In diseases associated with retinol deficiency, the dosage may be increased to the upper acceptable level consumption - 3000 mcg.

The above dosages refer 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 these two vitamins must be taken together.
Zinc deficiency can lead to impaired conversion of vitamin A to its active form. Because your body cannot synthesize vitamin A binding protein, the carrier molecule that transports vitamin A across the intestinal wall and releases it into the blood, without sufficient zinc, a zinc deficiency can lead to poor absorption of vitamin A to tissues. These two components are interdependent: for example, vitamin A promotes the absorption of zinc, and zinc also acts on 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 as they are dissolved in mineral oil from which the body cannot extract them. Permanent application mineral oil, thus, can lead to a lack of vitamin A.
For the normal absorption of vitamin A, the presence of fats and proteins in the diet is necessary. The difference between edible and mineral oil is that the body can absorb edible fat along with the vitamin A dissolved in it; Mineral oil is not absorbed by the body.

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, Β 3) Choline (Β 4) Pantothenic acid (Β 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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A group of fat-soluble compounds derived from b ionone. In nature, the most common are: retinol (vitamin A1, axerophthol, I), dehydroretinol (vitamin A2), retinal (retinene, vitamin A1 aldehyde, II), retinoic acid (III). Contained in animals ... ...

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VITAMIN E- Solution for injection Composition. 5 ml contains tocopherol acetate 300 mg. Indications. Hypovitaminosis E, infertility treatment. Application and doses. Intramuscularly or orally. Large animals 300 600 mg. Pigs, calves, sheep 100 200 mg. Dogs, cats... Imported veterinary drugs

A group of fat-soluble compounds derived from naphthoquinone. The most important representatives: phylloquinone (vitamin K1), multiprenylmenaquinones (vitamins K2 (30), K2 (35), differing in the length of the lateral isoprenoid chain, menadione (vitamin K3, lateral ... ... Biological encyclopedic dictionary

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 an essential 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 animal products. Vitamin A can also be synthesized directly in the human body from provitamin A supplied with plant food. Vitamin A does not dissolve in water, and in order for it to be absorbed and benefited by the body, a fatty environment is needed. Up to 50% of this vitamin is lost during cooking. 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 correct operation immune system, protects the body from many viruses and infections.
Vitamin A is important for of cardio-vascular system It prevents bad cholesterol from accumulating.
Helps the endocrine system to function properly.
The amount of this vitamin depends on the condition of the human skin. Sufficient intake of vitamin A helps to restore all layers damaged tissue and deal 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 state 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, prevent the onset and development of cancer.
During pregnancy, vitamin A is necessary not only for a woman, but also for a developing fetus for its normal nutrition and development.
This vitamin is very important for normal physical and mental development children and adolescents, as it is involved in almost all major bodily functions.

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

Daily requirement of the body for vitamin A:
The daily requirement for vitamin A depends on gender, age, physical and mental stress, weight, and even climate and season.
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 a hot period of time, during heavy physical exertion.

Foods 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 plant products.

Vitamin A sources (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 marine 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:
The lack of vitamin A in the body affects primarily 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), fragility of hair and nails, infertility in men, mental disorders, diseases of the digestive, endocrine, genitourinary and other systems of the body. And it's far from full list possible consequences.
Vitamin A deficiency can be corrected with vitamin-containing preparations, but this is done only as prescribed by a doctor.

An excess of 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 manifest itself in problems with the skin, hair and nails. Joint pain, disease internal organs, enlarged liver and spleen and other problems in the body can be caused by an excess of vitamin A. At the same time, it should be noted that foods rarely cause an excess of vitamin A in the body, especially if a person is balanced. As a rule, it is the intake of drugs to replenish vitamin A that most often causes an overabundance of this vitamin. These drugs should not be taken without consulting a doctor.

SAVE YOURSELF AND BE HEALTHY!

Vitamin A receives little attention in the media, and as a result, people are often unaware of how much they are consuming and how much they need to stay healthy. And this despite all the great evidence that indicates that vitamin A plays significant role in reducing the risk of many modern diseases. What is Vitamin A Really? This article will talk 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 includes retinol, retinoic acid, and also includes 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 when carotene enters the body it 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 about 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, which means that its content in supplements should be controlled.

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

How Vitamin A Works in the Body

The benefits of vitamin A for the retina of the eye 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, this causes 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 eventually leads to "night blindness".

Vitamin A plays an important role in the immune system and is essential for the body to produce cells for the innate and adaptive immune systems. These immune cells needed to kill pathogens and infections that would otherwise damage cells.

Vitamin A deficiency is strongly associated with increased risk development of modern diseases such as cardiovascular disease and cancer. It is not yet known exactly how vitamin A helps the body reduce the 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 body cells. The effect of vitamin A has special meaning for the skin, it converts immature skin cells into mature ones.

Integuments have a greater resistance when pathogenic microbes enter directly onto 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 just necessary.

Vitamin A, what foods contain

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 to retinol before the body can use this vitamin. This transformation is not a very efficient source for a sufficient intake of the vitamin in our body.

Animal sources of vitamin A (oily 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 one can understand that the body lacks vitamin A, these include: poor wound healing, decreased vision, dandruff, skin affected by a rash, premature wrinkles, soreness, weight loss, loss of appetite.

There are also known signs of an overabundance of vitamin A: sluggish general state, menstrual disorders, nausea, gait disturbance, pain in the bones.

Conclusions on 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 disease. Especially importance it has for the immune system, for the health of the skin and for good vision.

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

Vitamin A - video

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