Is vitamin a available in powder form? Vitamin a - what is useful for the body. The use of vitamin A

Vitamin A (Retinol) - a representative of the class of fat-soluble vitamins, is able to accumulate in the body. Essential for vision and bone growth, healthy skin and hair, normal immune system function, etc. Unstable in its pure form, found in both plant foods and animal sources.

Vit. A was discovered in 1913. Then two groups of scientists, independently of each other, found that the yolk of a chicken egg and butter contain a certain substance that stimulates the growth of animals.

After that, during the First World War, numerous cases of xerophthalmia and keratophthalmia, dryness and pathological keratinization of the sclera and cornea of ​​​​the eyes were described. At the same time, the relationship of these diseases with a deficiency of butter in the diet was noted.

The substance isolated from butter was originally designated as fat-soluble factor A. Later, in 1916, it was renamed vit. A. In 1921, signs of beriberi A were described, in 1931 the structure of the vitamin was described, and in 1937 Vit. A was obtained in crystalline form.

Varieties

In addition to Retinol vit. A includes a group of vitamers, substances similar in chemical composition and in their action. These substances are called retinoids. In addition to Retinol (vit. A 1), this includes its derivatives:

• Retinal is an aldehyde form of vit. A 1
• 3-dehydroretinol (vit. A 2) - trans-isomer of Retinol
• 3-dehydroretinal is the aldehyde form of vit. A 2
• Retinoic acid is the acidic form of vit. A 2
• Retinyl acetate, retinyl palmitate are ether derivatives of Retinol.

These are just the basic shapes. Along with them, there are many other retinoids that occur naturally or are formed in the body of humans and mammals during metabolic reactions. The functions of many of them remain poorly understood. By the name of the main component, A 1, this vitamin is commonly called Retinol.

Physical properties

The chemical name of Retinol is trans-9,13-Dimethyl-7-(1,1,5-trimethylcyclohexen-5-yl-6)-nonatetraen-7,9,11,13-ol (as palmitate or acetate). Formula - C 20 H 30 O. This chemical compound is a yellowish prismatic crystals with a specific odor and a melting point of 64 0 C.

It dissolves well in fatty substances and other organic solvents - ethyl and methyl alcohols, dicyclohexane, dichloroethane. Practically insoluble in water. Unstable in the environment - is destroyed by atmospheric oxygen and solar ultraviolet radiation. Other substances from the group of retinoids have similar properties.

Physiological action

• Metabolism

With its participation in the body, many redox reactions are carried out. It regulates all types of metabolism. It stimulates protein biosynthesis, activates many enzyme systems.

• Immunity

Retinol is an excellent immunomodulator. It enhances the phagocytic activity of leukocytes, stimulates the production of antibodies, participates in the synthesis of interferon and lysozyme. Thus, it strengthens the immune system and increases the body's resistance to many types of bacterial and viral infections. It is also an excellent antioxidant that prevents free radical damage to tissues. Antioxidant and immunostimulatory action leads to the fact that atypically changed cells are recognized in time, destroyed, and cancerous tumors do not develop.

• Skin and mucous membranes of internal organs

Vitamin A normalizes the growth and division of epithelial cells, prevents excessive keratinization. It also stimulates collagen synthesis. As a result, the barrier resistance of the mucous membranes of the respiratory, gastrointestinal tract and genitourinary system to the action of pathological agents increases. The skin under its action becomes elastic, without wrinkles, edema, age spots and other signs of aging.

• The cardiovascular system

Reduces the formation of low-density cholesterol, which is responsible for the formation of atherosclerotic plaques. Being an antioxidant, it prevents sclerotic and dystrophic changes in the myocardium.

• Musculoskeletal system

Increases the strength of ligaments, bones, cartilage. Promotes the growth of bones in length.

• Endocrine system

Retinol is involved in the synthesis of adrenal and sex hormones. It also reduces the level of thyroxine in case of its excessive production by the thyroid gland.

• reproductive system

In men it stimulates spermatogenesis, in women it ensures the normal course of the menstrual cycle. During pregnancy, this vitamin, along with other factors, forms the growth and proper development of the fetus.

• visual system

It has a tremendous impact on the state of the visual analyzer. Retinal is part of Rhodopsin. This visual pigment provides light sensitivity to the rod receptors in the fundus. Precursors of Retinol, carotenoids, moisturize the cornea and sclera, prevent their pathological keratinization (hyperkeratosis), the development of cataracts. And this vitamin also maintains in proper condition the function of the macula - the place of greatest visual perception of the retina.

daily requirement

In this table, IU are international units that reflect the activity of the drug. As for vit. And, here 1 IU corresponds to 0.3 mcg.

Signs of deficiency

A typical manifestation of beriberi A - the so-called. night blindness or hemeralopia, deterioration of twilight vision. Also, from the side of the eyes, keratomalacia, xerophthalmia will be noted, manifested by softening, dryness of the cornea, redness of the sclera with pathological lacrimation. In this case, visual acuity will be reduced, often a cataract is formed.

At the same time, the skin is dry, flaky, with an unhealthy color, pustular rash and reduced elasticity. Favorable conditions are created on such skin for various dermatitis, psoriasis, eczema.

The barrier function of the mucous membranes of the internal organs decreases. In combination with low immunity, this will be accompanied by frequent bronchitis, pneumonia, erosive and inflammatory processes in the gastrointestinal tract, inflammation of the genitourinary system with urinary incontinence.

The reproductive system suffers - the menstrual cycle in women is disturbed, the man complains of erectile dysfunction and early ejaculation. Often formed male and female infertility.

There is a general weakness, increased fatigue, drowsiness during the day and insomnia at night. On the part of the psyche, unmotivated irritability, anxiety and depression are noted. There is an increased risk of malignant tumors, especially breast cancer, and in smokers and those who often suffer from colds - lung cancer.

Deficiency predisposes:

• lack of intake of Retinol and carotenoids with food
• diseases of the gastrointestinal tract, in which its absorption is disturbed
• deficiency of other nutrients, in particular, zinc, vit E (Tocopherol), vit B 4 (choline).

Avitaminosis, as a rule, develops with a combination of these adverse factors.

In addition, under some conditions, the need increases. This:

• physical exercise
• psycho-emotional stress
• period of growth and puberty
• x-ray studies
• taking cholesterol-lowering drugs
• diabetes
• stay in a hot climate
• increased load on the visual analyzer (long sitting at the computer, watching TV)
• alcohol abuse
• pregnancy and breastfeeding.

Foods rich in vitamin A

Retinol enters the body with food. The content of vit. And in 100 g of food products:

It is easy to see that the largest number of vit. And it is found in products of animal origin, while in greens and vegetables it is not so much. Although you should not completely focus on the data from the table. The fact is that in most well-known products, vitamin A is not represented by Retinol, but by its precursors, provitamins, carotenoids.

These substances include alpha, beta and gamma carotene. The most active of them is beta-carotene. This is a natural pigment of bright red color, which is transformed during metabolic processes.

Especially a lot of beta-carotene and other carotenoids in vegetables and fruits that have an orange-red color. Red carrots are not rich in vitamin A, as many believe, but in its provitamin, beta-carotene. In general, carotenoids are found mainly in plant foods, while animal foods are rich in Retinol - milk, cheese, cod liver and liver of mammals, egg yolk. In addition, in terms of its activity, beta-carotene is many times weaker than Retinol - 12 μg of this provitamin is equivalent to 1 μg of Retinol.

Synthetic analogs

The most commonly used in clinical practice are Retinol acetate and Retinol palmitate. These medications are available in the following dosage forms:

• dragee 3300 IU
• capsules with oily solution for oral administration 3300 IU
• capsules with oily solution for oral administration 5000 IU
• capsules with oily solution for oral administration 33000 IU
• coated tablets 33000 IU
• solution for external use 3.44%, 100,000 IU/ml
• injection solution 0.86%, 25,000 IU/ml
• injection solution 1.72%, 50,000 IU/ml
• injection solution 3.44%, 33,000 IU/ml.

Injections of oil solutions are done only intramuscularly, they should be done into a vein by no means! A solution for external use is used in the treatment of skin diseases, and preparations for internal use are used to prevent beriberi A and treat conditions associated with it.

To prevent the development of hypervitaminosis A, you must carefully follow the dosages that the doctor determines. Usually drugs with a content of 3300 IU are used for prophylactic purposes, and more “heavy” dosage forms are used for therapeutic purposes.

Along with Retinol acetate and palmitate, vitamin A is present in many vitamin and mineral complexes, including:

• Supradin,
• Duovit,
• Complivit,
• Vitrum,
• Aevit, and many others.

In addition to pharmaceuticals Vit. It is included in many dietary supplements and cosmetic products for skin and hair care. Unlike natural Retinol, which breaks down quickly, synthetic retinoids are more stable and retain their properties for quite a long time.

Indications for use

Along with the prevention and treatment of beriberi A, synthetic retinoids as part of complex treatment are used in the following conditions:

• eye diseases with damage to the eyelids, sclera, cornea, retina - hemeralopia, retinitis pigmentosa, keratomalacia, xerophthalmia and keratophthalmia
• diseases of the stomach and intestines, the consequences of operations on the gastrointestinal tract with malabsorption of vit. A
• skin diseases and injuries - eczema, psoriasis, seborrheic dermatitis, neurodermatitis, mild burns and frostbite
• acute and chronic infections, incl. influenza, pneumonia, bronchitis, childhood infectious diseases (measles, scarlet fever, chicken pox, etc.).
• rickets in children
• malignant tumors of the skin, leukemia.

Metabolism

The absorption of Retinol, which is part of food products and drugs, is carried out in the upper sections of the small intestine. As part of the food comes esterified Retinol (in the form of esters) or carotenoids. In the intestinal lumen, under the action of pancreatic and enteric enzymes, Retinol esters are destroyed (hydrolyzed, emulsified) with the formation of free Retinol.

Further, in the mucous membrane of the small intestine, with the participation of specific enzymes, esters of Retinol fatty acids are again synthesized. In this form, it enters the lymph and in its composition is delivered to the liver. Here it is deposited in the form of the ether compound Retinyl palmitate. In addition to the liver, vitamin A is deposited in the lungs, kidneys, retina, adrenal glands, mammary glands, and adipose tissues.

But still, the main depot is the liver - up to 80% of vit. And in the form of Retinyl palmitate. In case of insufficient income or with its increased consumption, these reserves may be enough for 2-3 years. If necessary, Retinol from the liver with the participation of zinc is released again and binds to the protein transthyretin. Then it is delivered to the cells of organs and tissues, where it combines with retinol-binding protein (RBP), which is also synthesized by the liver.

Being chemically an alcohol, Retinol destroys cell membranes. Therefore, before entering the cell, Retinol is transformed into Retinal and Retinoic acid. In comparison with Retinol, these compounds are milder and do not have a destructive effect on cells. Carotenoids are absorbed in the intestine 6-12-24 times worse (depending on the type). Their transformation into Retinal is carried out in the cells of the small intestine with the participation of a specific enzyme containing iron.

The activity of this enzyme depends on the state of the thyroid gland. With its insufficient function (hypothyroidism), this process will be disrupted, and unutilized carotenoids will accumulate in the body. In this case, pseudo-jaundice will be noted - staining of the skin and mucous membranes in a rich yellow color.

Vit. And it is better absorbed in combination with fats and proteins. Therefore, starvation, restrictive diets, passion for plant foods - all this makes it difficult for the absorption of vit. And it contributes to its deficiency. It is also difficult to absorb Retinol in diseases of the liver, gallbladder and pancreas, when its emulsification and hydrolysis are disturbed. The unabsorbed part of vit. And in the form of various metabolites is removed through the kidneys and intestines.

Interaction with other substances

• Zinc

Promotes the release of vitamin A from the depot. Therefore, against the background of a deficiency of this mineral, activation will be slow.

• Dietary fats and proteins

Facilitate the absorption of vitamin A in the small intestine.

• Vegetable oils, laxatives

Being fat soluble, vit. A easily dissolves in these substances and is removed from the intestines. Therefore, regular intake of vegetable oils will lead to malabsorption.

• Enterosorbents

They also interfere with the absorption of Retinol.

• Vit. E (Tocopherol)

Prevents destruction. Therefore, a deficiency of vit. E is often accompanied by a deficiency of vit. A. For this reason, it is advisable to take both vitamins together.

Signs of hypervitaminosis

Due to the ability to accumulate, the daily dose of Retinol for children should not exceed 900 mcg, and for adults - 3000 mcg. Eating only food rich in vit. A is unlikely to cause hypervitaminosis A.

Although one remarkable case was described in medical practice, when a group of polar explorers decided to eat the liver of a polar bear. In a harsh climate, the body of this animal has adapted to accumulate vit. And in huge quantities. And since the main depot of the vitamin is the liver, the polar explorers got a real poisoning with Retinol, and most of the unfortunate people died. But such cases are unique, and are not the rule.

Basically, hypervitaminosis A develops with an overdose of synthetic retinoids or when they are combined with food rich in vit. A. The main signs of hypervitaminosis A:

• abdominal pain, diarrhea
• nausea, vomiting
• general weakness
• hepatomegaly and splenomegaly - enlargement of the liver and spleen in size
• redness and itching of the skin, sweating at night
• pseudojaundice
• hair loss, dandruff
• drowsiness, insomnia
• bleeding gums, mouth ulcers
• soreness and swelling of soft tissues
• muscle cramps
• confusion.

In pregnant women, an overdose of Vit. And it can provoke a teratogenic effect - a violation of embryonic development and the appearance of deformities in the fetus.

The trouble is that due to some similarity of manifestations, hypervitaminosis A can be mistaken for its deficiency. And then, instead of stopping taking the vitamin and changing the nature of the diet, on the contrary, increase its dosage and take food rich in Retinol and carotenoids. To prevent this from happening, with any alarming symptoms, you need to consult a doctor and undergo the necessary laboratory tests.

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 of fungi.

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 RE, 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 insufficient amounts of carotene and retinol, i.e., they cannot serve as full-fledged sources of vitamin A.

Animal foods containing vitamin A:

• beef liver;
• Cod liver;
• fish fat;
• sea ​​fish caviar;
• 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 in the 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 of bone tissue, as well as enamel and dentin. Thanks to him, the fat reserves necessary for a person are formed.

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 developing macular degeneration, 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) of oncological diseases. In clinical studies, it has been proven that b-carotene reduces the likelihood of recurrence of malignant neoplasms after surgery.

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

Vitamin A is able to increase the serum concentration of high density lipoproteins necessary for the body.

The carotenoid lycopene, which is found in large quantities in tomatoes, prevents the deposition of cholesterol on the vascular walls, thus protecting a person from its dangerous consequences. This provitamin also reduces the likelihood of developing malignant and mammary glands, 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 a bacterial and viral nature (the phagocytic activity of leukocytes is significantly increased).

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

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

The constant presence of a sufficiently high level of retinol in the serum 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:many modern cosmetic preparations include retinoid substances, 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 improves the functional activity of the bronchi and lungs. Receiving vitamin A preparations for patients can speed up recovery from such pathologies of the digestive tract as 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 the normal intrauterine development of the unborn 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. For nursing mothers, the norm recommended by Russian doctors is higher - 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 can affect the body's need for vitamin A. Cold weather has no effect on retinol metabolism, but a 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 of "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 prescribed orally, for injection (IM) or for topical 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. For skin diseases, the dosages are higher - 50000-100000 and 5000-10000 IU, respectively.

Hypervitaminosis

Important:vitamin A has a toxic effect on the body when consumed 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.

Chem. Name: retinol, dehydroretinol;
Solubility: fat soluble;
Diseases from deficiency: xerophthalmia, night blindness;
Max level: 3000 mcg;

Vitamin A (retinol, from English. carrot - carrot) belongs to the group of fat-soluble vitamins and antioxidants, and takes part in many physiological processes. Vitamin A is the first representative of its group, isolated in its pure form, and named after the first letter of the alphabet.

It was synthesized from carrots, thanks to which the second name was obtained - retinol. At the end of the 19th century, scientists discovered that Vitamin A is found in pure form only in animal products..

Carrots and other plants contain a proretinoid called carotene. It turns into retinol only when it enters the body. But this discovery doesn't make vegetables and fruits any less important sources of vitamin A.

What is Vitamin A good for?

Retinol- An antioxidant that reduces the damaging effects of free radicals on cell walls. It affects the differentiation of fetal tissues. The normal operation of the following systems depends on vitamin A:

The immune system

• has an antitumor effect
• needed to ensure full phagocytosis;
• increases the resistance of mucous membranes to the action of microorganisms;
• stimulates the work of humoral (antibodies) and cellular immunity.

Nervous system

• responsible for normal twilight vision;
• protects the brain from free radical damage;
• affects the formation of the nervous system in the fetus.

Digestive system

• stimulates glycogen synthesis;
• accelerates the formation of proteins in the liver;
• increases the content of good cholesterol in the blood;
• prevents infection of the gastrointestinal tract.

Skin and mucous membranes

• necessary for the normal state of skin derivatives - hair and teeth;
• responsible for the timely renewal of skin cells;
• controls the normal functioning of the mucous membranes;
• facilitates the course of skin diseases.

daily requirement

Our body is able to accumulate retinol. With a significant increase in the dosage of the drug, intoxication may occur, in order to prevent an excess of vitamin A in the blood, it is necessary to control the dose.

The need for retinol increases in people who perform heavy physical work and receive a large load on their eyesight. The dosage is increased for patients with vitamin A deficiency, pregnant and lactating mothers.

What foods contain vitamin A

Most Retinol among plants contain yellow vegetables and fruits - carrots, pumpkin, apricot, melon and sea buckthorn. It is also abundant in rose hips, viburnum, parsley, tomatoes, hawthorn and dill.

Food table with Vitamin A

Preparations with Vitamin A

Types of drugs

The pharmaceutical industry produces vitamin A in several forms. This allows patients to choose the most appropriate treatment option for them. In pharmacies, retinol can be found in the form of such preparations:

1. Vitamin A in oil- is available for injection, internal and external use both in pure form and as part of multivitamin preparations.
2. Vitamin A capsules- used for oral administration. This is the same oil solution of retinol, but it is more convenient to dose it, and the capsule allows you not to feel the specific taste of the vitamin.
3. Vitamin A in the form of an ointment- available for external use in the treatment of skin diseases. At observance of dosages does not cause a significant increase in the level of retinol in the blood.
4. Vitamin A tablets- available for adherents of tablet forms, and those who have allergic reactions to the components of other retinol preparations.

Preparations

digestibility

The absorption of vitamin A depends on the presence of tocopherol (vitamin E) in the diet, which plays the role of a stabilizer-antioxidant. Retinol dissolves only in fat, so low-fat foods slow down its absorption. Vitamin A-based preparations should be taken no earlier than 10-15 minutes after eating.

Proretinoids are better absorbed in the presence of zinc, and this element should be present in the diet. While taking retinol, the body must be provided with B vitamins, phosphorus and calcium.

Compatibility and interaction with other drugs

Do not drink alcohol while taking retinol. This combination can cause liver damage. It is undesirable to take it simultaneously with other retinoids, as this leads to vitamin A hypervitaminosis.

The same effect gives the simultaneous use of retinol and oral contraceptives. The intake of the latter increases the amount of protein in the blood that is responsible for the transport of vitamin A.

Laxatives of mineral origin, amyl nitrite and cholestyramine slow down the absorption of vitamin A. With their simultaneous use, dose adjustment of the latter is necessary.

Taking tetracyclines along with retinol can cause an increase in intracranial pressure. Glucocorticoid steroids are direct vitamin A antagonists.

Vitamin A deficiency

If the body stops receiving retinol from food, then the reserves accumulated in the liver will be used for some time. Vitamin A deficiency occurs when it is absent from the diet for a long time. WITH

The most well-known symptom of hypovitaminosis A is night blindness. With this disease, a person begins to see poorly at dusk, up to complete loss of vision in the absence of normal lighting.

This is due to the fact that retinol is necessary for the synthesis of purpura, the substance responsible for the light sensitivity of the eyes. With a lack of vitamin A, other symptoms appear, such as:

Vitamin A deficiency symptoms

• dry skin and its derivatives (nails and hair);
• lethargy and suppression of appetite;
• decreased immunity, manifested by frequent infections;
• weight loss up to extreme exhaustion;
• insomnia and mental disorders;
• decrease in potency;
• skin rash;
• problems with fertilization up to infertility;
• the risk of oncology increases;
• in children and adolescents, growth slows down;
• due to the weakening of tooth enamel, caries develops.

Vitamin A overdose

The human body is not able to quickly remove retinol. Despite this, an excess of vitamin A in the diet cannot lead to intoxication. The extra vitamin will not be absorbed.

Vitamin A hypervitaminosis occurs with a severe overdose of pharmaceutical forms of the drug. Pathology is accompanied by the following symptoms:

Vitamin overdose

• bleeding from the gums;
• enlargement of the liver and spleen;
• fragility of nails and hair;
• dry skin;
• migraine;
• vomit;
• diarrhea;
• lethargy and oppression;
• in pregnant women, miscarriages and fetal developmental disorders are possible.

Video Vitamin A

Kalorizator 2020 - Vitamins, instructions for medicines, proper nutrition. All information is for informational purposes only. When treating, be sure to consult a doctor.

Vitamin A, otherwise known as retinol, is a fat-soluble vitamin that is an antioxidant. It was opened one of the first in 1913 and in accordance with this received the designation of the first letter of the Latin alphabet. For the first time, vitamin A was obtained from carrots - therefore, all A vitamins are called carotenoids (from the English carrot). Carotenoids are found in mushrooms, meat, plants and, when ingested, are converted into vitamin A.

Vitamin A in foods

The best sources of vitamin A are liver and fish oil. Next in descending order are egg yolks, butter, whole (not skimmed) milk and cream. The products-suppliers of this vitamin of plant origin are yellow and green vegetables (carrots, sweet peppers, pumpkin, spinach, green onions, parsley), apricots, peaches, apples, watermelons, melons, grapes, cherries, rose hips, legumes (peas and soybeans) . In addition, some medicinal herbs contain vitamin A: fennel, horsetail, hops, lemongrass, nettle, mint, raspberry leaves, sage, sorrel.

Vitamin A in animal products is represented by fish oil, caviar, beef liver, butter, margarine, whole milk, sour cream, cottage cheese, egg yolk, cheese.

Action of vitamin A

The effect of vitamin A on the human body is enormous. It is actively involved in redox processes, contributes to the regulation of protein synthesis, the normal functioning of metabolism, the performance of the functions of subcellular and cellular membranes, the formation of teeth and bones, including body fat. Vitamin A is necessary for the full growth of new cells in the body and slows down the aging process. In addition, the vitamin is an essential element that allows you to ensure the normal functioning of the human immune system.

The use of retinol in sufficient quantities can increase the protective function of the mucous membranes, increase the activity of leukocytes and other elements of nonspecific immunity. This substance protects our body from infections, colds, flu, diseases of the urinary system and gastrointestinal tract. The presence of a sufficient amount of vitamin A in the blood of children from developed countries explains the fact that they more easily tolerate infectious diseases such as chickenpox, measles, while in countries with a low standard of living, mortality from these seemingly harmless childhood diseases is widespread.

Vitamin A or its synthetic analogues - retinoids - are an integral element of all cosmetic products aimed at restoring the tissues that make up the mucous membranes and skin. Vitamin is used as a medicine to eliminate skin diseases of various etiologies (psoriasis, acne, pimples). With sunburn, vitamin A stimulates collagen production, speeding up regeneration processes and reducing the risk of infection.

Being a powerful antioxidant, vitamin A is an excellent prophylactic against cancer, protects the body's cell membranes from the damaging effects of oxygen free radicals and polyunsaturated acids. In addition, the action of retinol extends to the cardiovascular system, preventing the occurrence of heart disease and increasing the level of "useful" cholesterol in the blood.

The main carotenoids, zeaxanthin and lutein, play a critical role in protecting our eyes by reducing the risk of cataracts and macular degeneration.

Vitamin A requirement

According to studies, no single product can compensate for the lack of vitamin A in the body, if any, therefore, in order to eliminate the deficiency, additional intake is necessary. The recommended daily dose of vitamin A is:

• 3000 IU (900 mcg) for men;
• 2300 IU (700 mcg) for women.

In diseases associated with a lack of retinol in the body, the daily dosage of the vitamin can be increased to 10,000 IU. It is not recommended to take more than 6000 IU of the vitamin per day for pregnant women, since large amounts of retinol can have a teratogenic effect on the intrauterine development of the fetus.

With caution, vitamin A should be taken by patients with asthmatic manifestations of allergic diseases. Retinol should also be avoided in people with hypothyroidism.

Indications for the use of vitamin A

The use of retinol is advisable for:

• Diseases of the mucous membranes and skin lesions (burns, seborrheic eczema, candidiasis, allergic dermatoses);
• Eye diseases (keratitis, conjunctivitis);
• The need to activate the processes of tissue regeneration and healing after surgery, fractures, burns, wounds.

In addition, vitamin A is an integral component of complex therapy in the treatment of:

• Acute and chronic diseases of the biliary tract and liver;
• Acute and chronic pneumonia;
• iron deficiency anemia.

Signs of vitamin A deficiency (hypovitaminosis)

Retinol deficiency is characterized by a serum vitamin A content below 0.35 µmol/L. Clinically significant symptoms of vitamin A deficiency in the body are:

• Dandruff;
• Premature aging of the skin;
• Increased temperature and pain sensitivity;
• Sensitivity (hyperesthesia) of tooth enamel;
• Accumulation of mucus or hardened crusts in the corners of the eyes, increased tearing in the cold;
• Accelerated ejaculation, weak erection in men;
• Weak sphincter of the bladder;
• Hemeralopia ("night blindness");
• Frequent colds, respiratory infections, chronic pneumonia;
• Anemia, exhaustion, insomnia.

The causes of vitamin A deficiency in the body are:

• Unbalanced diet;
• Inadequate dietary intake of retinol;
• Limiting fat intake;
• Diseases of the digestive tract;
• Malabsorption syndrome;
• Resection of the small intestine;
• Insufficient intake of vitamin E, an antioxidant that prevents the oxidation of retinol.

Signs of too much vitamin A (hypervitaminosis)

Signs of a retinol overdose are similar to those of a vitamin A deficiency. These include:

• Pigmentation and dry skin, brittle nails, hair loss;
• Delayed menstruation, abdominal pain, dyspeptic disorders;
• Articular pain, diffuse thickening of the bones;
• Enlargement of the spleen and liver.

special instructions

According to medical research, the interaction of vitamin A with alcohol leads to liver damage to a greater extent than when taking an alcoholic drink alone. This fact should be borne in mind when using alcohol-containing drugs.

Vitamin A is a group of 4 chemicals: retinol, dehydroretinol, retinoic acid, and retinal. They are all different forms of vitamin A and affect different organs. For ease of perception and memorization, it is customary not to separate the functions of these substances and describe what vitamin A is useful for, in the aggregate of its forms.

What is vitamin A useful for, why does the body need it

The role of vitamin A in the human body cannot be overestimated. It is involved in the preservation of immunity, acts as an antioxidant, is necessary for vision, and is involved in redox processes. It plays an important role in metabolism and in the structure of bone tissue, teeth and hair, improves metabolism.

By supporting immune T-cells, vitamin A fights tumors and slows down cell aging, which allows a person to look younger. It also improves the growth of the embryo, is responsible for the concentration of cholesterol in the blood and is involved in the synthesis of steroid hormones. This list of positive qualities does not allow us to question the benefits of vitamin A.

Group A vitamins

The group of retinoids by origin is usually divided into two forms: retinol contained in animal products, and carotene - from plant products, this is the precursor of retinol. The importance of vitamin A for the body is difficult to overestimate, knowing how it affects the human body.

First of all, it affects vision, being part of the visual pigment, which is responsible for the light and color perception of the eye. It prevents damage to cellular DNA, preserves the integrity of cells, improves tissue healing and is involved in the formation of red blood cells. In addition, it increases the number of leukocytes - the main defenders of the human body, improves immunity, reducing the risk of infectious diseases by 2-3 times.

Vitamin A is found in some cosmetic products. Retinoic acid is able to stimulate the production of collagen in the skin, which is responsible for elasticity and youth. For men and women, the compound is useful in that it affects the synthesis of sex hormones - testosterone and estrogen, and therefore participates in the maturation of germ cells.

A valuable quality of beta-carotene is the neutralization of free radicals, which is used for the prevention and treatment of cancer.

Daily rate

Depending on age and gender, the daily intake of a vitamin for the human body will be different. It is customary to calculate it in milligrams or in IU (international units). Pregnant women should take vitamins of group A for the normal development of the fetus and continue to provide the child with retinoids and carotenoids after birth. The following table will help you calculate the optimal dose:

Read also The need of the adult human body for vitamin B12: what is it for, daily allowance, content in products

The daily requirement for the human body may increase under certain circumstances:

• when breastfeeding;
• with daily sitting at the computer;
• during physical activity;
• in hot climates;
• during active growth of the body;
• with alcohol abuse.

With a shortage of retinoids and carotenoids in food, they should be taken in the form of dosage forms.

List and table of products

Which products contain a group of retinoids, the table will help you figure it out.

The human body should receive 1/3 of retinol and 2/3 of beta-carotene, since the activity of the first is 3 times higher than the activity of the second. This means that in the daily diet you need to include a large number of vegetables and fruits of bright red, yellow and orange colors.

Top 10 foods with the highest content

Retinol takes part in the work of the cells of the human body, and carotenoids must first be converted from plant foods into a bioavailable form. To get 1 unit of retinol, you need to process 3 units of carotenes. Therefore, to obtain the daily norm of vitamin A, it is more expedient to eat a piece of beef liver than several kilograms of peaches. This means that in the list of products containing vitamin A, the main places belong to products of animal origin.

Of all the foods that contain vitamin A, most of it is in any liver. It can be consumed in the form of various dishes or bought dried in capsules.

• 1st place - fermented cod liver oil or cod liver itself (cooked, a lot and canned);
• 2 - beef, lamb or chicken liver;
• 3 - chicken yolks;
• 4 - butter and cream;
• 5 - carrots (the leader in the content of carotene among vegetables);
• 6 - red rowan;
• 7 - parsley and dill;
• 8 - spinach and celery;
• 9 - dried apricots;
• 10th place - wild rose and sorrel.

Instead of eating vegetables and fruits, you can also drink freshly prepared juice from them, which will also have a beneficial effect on health.

Drugs in a pharmacy, list and instructions for use

If an insufficient amount of carotene and retinol enters the body with food, you need to take them in the form of drugs. Today, their assortment in pharmacies is large, and the choice depends on the preferences of the buyer himself.

Vitamin A is produced:

• in the form of capsules: retinol acetate 3300, 5000, 33000 IU; etretinate (tigazon) 0.01 and 0.025 g each; isotretinoin (roaccutane) 2.5, 5, 10 and 20 mg;
• in the form of tablets of 33,000 IU (retinol acetate and retinol palmitate);
• in the form of a solution for injection in ampoules of 25,000, 50,000, 100,000 IU / 1 ml (retinol acetate);
• in a dragee of 3300 IU (retinol acetate and retinol palminate);
• in an oil solution for oral administration of 100,000 IU / ml in 10 ml vials;
• in an oil extract from the liver of cod fish in vials of 50 and 100 mg;
• in the form of a cream 0.05% or 0.1% in tubes of 20 g.

In the pharmacy you can find the following names of vitamin complexes containing retinol: Aevit, Gendevit, Undevit, Akvital and various multivitamin preparations - Centrum, Complivit, Revit, Alphabet, etc.

To get the therapeutic effect of retinoids and avoid overdose, you need to know how to properly take vitamin A. The dose depends on age and gender.

Intramuscularly, an oil solution of vitamin A is administered, taking into account the nature of the disease, in the form heated to body temperature: for adults - 10,000-100,000 IU, for children - 5,000-10,000 IU.

For the treatment of burns, wounds or ulcers, an oily solution is used in the form of compresses, which are applied to the lesion 5-6 times a day.

With long-term treatment of eye diseases, injections alternate with oral retinol.

Pregnant women and children should be taken with caution.

Some factors require an increased or decreased intake of retinoids. So, people who are on a diet and do not get enough fat need additional vitamin A supplements. Diseases of the liver, intestines, gallbladder lead to a lack of retinol in the body. While the use of oral contraceptives and hormonal agents, on the contrary, reduce the need for it.

What can a deficiency lead to?

The lack of retinoids in the body is fraught with unpleasant, and sometimes serious consequences. So, vitamin A deficiency can lead to:

• peeling and premature aging of the skin;
• skin rash;
• reduced body resistance to various diseases;
• dry eyes and decreased visual acuity;
• conjunctivitis and cataracts;
• dandruff and hair loss;
• decreased appetite;
• development of cardiovascular diseases, etc.

Since retinol and carotene play the role of powerful antioxidants, vitamin A is responsible for the prevention of cancer and contributes to their treatment. The lack of retinoids can adversely affect the course of oncological processes.

Contraindications

Do not use preparations containing retinoids for people with hypersensitivity to these compounds. Vitamin C should be taken with caution by those suffering from alcoholism, cirrhosis of the liver, viral hepatitis, and renal failure. During pregnancy (especially in the 1st trimester), lactation, as well as in childhood or old age, the vitamin is also prescribed with caution.

It must be remembered that an excess of this bioorganic compound is no less dangerous than its deficiency. Hypervitaminosis occurs due to the fact that retinol is able to accumulate in tissues, therefore the prescribed daily dosage cannot be violated.

The side effect of vitamin A, in addition to pain at the injection site, is associated with symptoms of its overdose, which can be acute or take the form of chronic intoxication.

Acute overdose (observed 6 hours after drug administration):

• double vision;
• dizziness;
• irritability;
• osteoporosis;
• bleeding from the gums;
• dryness, the appearance of ulcers in the mouth;
• peeling of the lips, palms;
• confusion:
• increased intracranial pressure;
• Strong headache;
• nausea and vomiting;
• diarrhea;
• drowsiness

Chronic intoxication:

• loss of appetite;
• bone pain
• cracks and dry skin;
• dryness of the oral mucosa;
• gastralgia;
• hyperthermia;
• photosensitivity;
• hair loss;
• yellow-orange spots on the soles and palms, in the region of the nasolabial triangle;
• convulsions and many others.

Treatment for overdose is drug withdrawal and treatment of symptoms.

Vitamin A is a useful and necessary bioorganic compound for the human body. However, taking it thoughtlessly and in free quantities is wrong and dangerous. Before use, you should consult a doctor who will prescribe the right dose, taking into account all the individual characteristics of the patient.