Vitamin a. Chemists have shown how blue light destroys the retina. A vitamin derivative is part of the visual pigment.

Of course, we have all heard aboutvitamin A– that it is contained in carrots and is extremely important for vision. And when eating carrot juice, you should wash it down with fresh cream. But is this vitamin A so simple?

In fact, vitamin A is not like other vitamins we know. It is not a single chemical substance, but a general name for various compounds that have a common biological effect. One group, which includes retinol, retinal and retinoic acid, forms the vitamin A complex and is calledretinoids. Another group - pro-vitaminscarotenoids(primarily β-carotene) are capable of being transformed into retinol in the human body (however, only 10%). Despite the fact that both groups of substances have a unidirectional effect, the body receives them from different sources. What they also have in common is that they are absorbed with the participation of fats (therefore vitamin A is a fat-soluble vitamin).

Source retinoidsare animal products. Particularly rich in retinolfish oil, eggs, butter, milk, beef liver. The amount of retinoids in products can be significantly reduced if stored improperly or if fats spoil (rancid). Overheating (prolonged boiling) of fat during cooking leads to the same result. Culinary losses of retinol during heat treatment of products can reach 40%.

Retinol plays a critical role in the development of skin cells and bone tissue, and also ensures the functioning of the visual analyzer, being included in the visual pigment rhadopsin, which provides photoreception on the retina. Radopsin synthesis is especially increased in low light conditions, providing dark adaptation. Retinoic acid is a necessary component of biochemical reactions involving thyroid hormones and vitamin D. These processes ensure proper intrauterine development, stimulate growth, influence the development of blood cells, and promote the mobilization of stored iron for hemoglobin synthesis. Vitamin A deficiency in the diet accelerates the development of iron deficiency anemia and prevents additional intake of iron from food. In addition, the most important function of retinol is its antioxidant activity.

As already mentioned, the main sources of retinol are animal products. Moreover, the more fat a product contains, the more vitamin A it contains. From a hygienic point of view, this means thatshould not be increased retinol intake from food sources. However, not everything is so bad - pro-vitamins A, carotenoids, can be converted into retinoids in the body, thus, the lack of vitamin A can be replenished through plant foods.

In this regard, let's talk aboutcarotenoids. Their name comes from the Latincarota- names of the carrot family from which they were first isolated. Carotenoids include substances with different A-vitamin activity: carotene, cryptosanthin, as well as compounds not related to provitamins: lutein, zeaxanthin and lycopene. β-carotene has the highest vitamin activity among other carotenoids. Carotenoids perform several important functions in the body: A-vitamin, antioxidant and regulatory (at the cellular level). Although β-carotene has low activity (compared to retinol), carotenoids make a major contribution to maintaining vitamin status. Lutein and zeoxanthin provide retinal protection by selectively absorbing blue light in the visible spectrum.

The main source of carotenoids is plant products, usuallyred and yellow vegetables and fruits . However, in some leafy plants, in particularspinach, the abundance of chlorophyll masks the yellow-orange pigment and gives them a green color. Main dietary sources of β-caroteneare carrots, pumpkin, apricots, dried apricots, spinach. Lycopene enters the body fromtomatoes. Particularly rich in lutein and zeoxanthinbroccoli, pumpkin, zucchini, spinach . To meet the real need for carotenoids, it is not enough to constantly consume any plant products - it is necessary to ensure that the listed products are regularly included in the diet. Culinary losses of carotenoids during thermal processing of products can also reach 40%. Carotenoids are especially unstable in the light.

The combination of foods containing carotenoids with dietary fats increases the availability of these vitamins, so it is advisable to use, for example, the following dishes in the diet:grated carrots or vegetable salad with 10% sour cream, milk pumpkin porridge with butter. It would also be correct to include apricots, oranges, watermelon, and peaches as a third course in lunch.

Given the fact that retinoids and carotenoids enter the body from completely different sources, they are currently classified separately. Attempts are being made to establish their independent standards for intake into the body, although they usually use the general total physiological level of their daily requirement, which is expressed inretinol equivalent . This indicator has sexual differentiation and for men is 1 mg/day, and for women - 0.8 mg/day. The need for retinol itself is set at 40% of the retinol equivalent, which corresponds to 0.4 mg for men and 0.32 mg for women. And the need for β-carotene is set at 5 mg/day.

Deep deficit vitamin A in the diet (vitaminosis) develops in the absence of animal and varied plant foods, i.e. in conditions of hunger. In developing poor countries, against the background of general protein-energy deficiency, the organ of vision is very often affected in children - xerophthalmia with the development of blindness. In this case, secondary immunodeficiency also develops, most often accompanied by infections of the respiratory tract and genitourinary system.

At long-term insufficient intake vitamin A (hypovitaminosis) the first signs of retinol deficiency are follicular hyperkeratosis and general dryness of the skin, mucous membranes (for example, conjunctiva), a decrease in the time of dark adaptation of the eye to twilight conditions (night blindness).

Extreme food excess retinol (hypervitaminosis) can occur as a result of eating foods such as the liver of a polar bear and some marine mammals - an extremely rare case for modern humans. Retinol poisoning has also been described, an excess of which has accumulated in a traditional food product - chicken liver due to technological violations in the use of the vitamin as a feed additive in poultry farming. However, hypervitaminosis A most often occurs due to additional medications taken in large dosages. With prolonged intake of quantities of retinol many times (more than 10-20 times) exceeding the physiological norm, headaches, dyspeptic disorders (nausea, vomiting), damage to the skin of the face and scalp (itching, flaking, hair loss), pain in the bones and joints.

Despite the fact that carotenoids can be transformed into retinol, their excess from food is not converted into vitamin A when the liver depot is saturated. With a high intake of β-carotene due to medications or as a result of consuming large amounts of foods rich in it (for example, carrot juice), carotenoderma can develop - a yellow coloration of the skin.

When studying the effect of large doses (20-30 mg/day) of carotenoids with long-term use, data were obtained on an increase in mortality from lung cancer among long-term smokers who took this vitamin. This result confirms the need for caution in the use of dietary supplements, including vitamins, in people at risk of developing cancer - almost any length of smoking is accompanied by such a danger.

The material was prepared based on information from open sources.

Despite the fact that dozens of scientific papers have been devoted to the negative impact of screens on humans, modern people spend more and more time “in the company” of a TV, computer and smartphone. However, it is worth noting that until now it remained unclear exactly how the display light works. But now, chemists at the University of Toledo have finally identified the mechanism by which blue light emitted from digital devices turns molecules in the retina into true cell killers.

The most important role in the process of vision is played by retinal, a form of vitamin A. This substance is part of the main visual pigments and is involved in the creation of nerve signals from which the brain forms an image. And since without retinal the photoreceptors become completely useless, it must be constantly produced in the retina of the eye.

In a new study, a team led by Ajith Karunarathne found that when exposed to blue light, retinal triggers reactions that produce substances that are toxic to retinal cells. It is this process that leads to age-related macular degeneration, when the immune system gradually ceases to protect cells from destruction.

In the experiment, scientists injected retinal into a variety of cell types, including heart, cancer and nerve cells, and then exposed the samples to light of different wavelengths. And each time, under the rays of the blue part of the spectrum, the cells died, while other types of lighting did not have a negative effect.

"It's really toxic. The photoreceptor cells in the eye don't regenerate, and when they die, it's permanent," study co-author Kasun Ratnayake explained in a university press release.

But there is good news: it turned out that the antioxidant alpha-tocopherol, a derivative of vitamin E, saves you from the tricks of retinal. Unfortunately, over time, when the body begins to age or when the immune defense weakens, the ability to fight the effects of blue light in this way disappears.

In the United States alone, two million new cases of macular degeneration are detected annually, a group of diseases that damage the retina and impair central vision. Understanding exactly how ubiquitous blue light affects human health offers hope for developing ways to protect the younger generation in a high-tech world.

Researchers are now measuring the intensity of light coming from the screens of various devices to simulate the reaction of eye cells to the natural radiation that people encounter in everyday life.

According to Karunaratne, you can protect yourself from natural blue light by using sunglasses that filter out these waves along with ultraviolet radiation. In addition, many gadget manufacturers today install appropriate software filters on their new devices. On older device models, users can install programs that filter out the blue component themselves.

More details about the results of the study can be found by reading published in Scientific Reports.

Let us also add that today there are known cases of retinal restoration, for example, with the help of and. However, for now these are only experimental developments. However, the authors of the Vesti...

Visual phototransduction is a complex of processes that is responsible for the change (phototransformation) of pigments and their subsequent regeneration. This is necessary to transmit information from the outside world to neurons. Thanks to biochemical processes, under the influence of light of different wavelengths, structural changes occur in the structure of pigments that are located in the lipid bilayer region of the membranes of the outer lobe of the photoreceptor.

Changes in photoreceptors

Photoreceptors of all vertebrates, including humans, can respond to light rays by changing photopigments, which are located in bilayer membranes in the region of the outer lobe of cones and rods.

The visual pigment itself is a protein (opsin), which is a derivative of vitamin A. Beta-carotene itself is found in foods and is also synthesized in retinal cells (photoreceptor layer). These opsins or chromophores in a bound state are localized deep in the bipolar discs in the area of ​​the outer lobes of the photoreceptors.

About half of the opsins are contained in a lipid bilayer, which is connected externally by short protein loops. Each rhodopsin molecule has seven transmembrane regions that surround the chromophore in the bilayer. The chromophore is located horizontally in the photoreceptor membrane. The outer disk of the membrane region has a large number of visual pigment molecules. After a photon of light has been absorbed, the pigment substance passes from one isoform to another. As a result of this, the molecule undergoes conformational changes, and the structure of the receptor is restored. In this case, metarhodopsin activates the G protein, which triggers a cascade of biochemical reactions.

Photons of light affect the visual pigment, which leads to the activation of a cascade of reactions: photon - rhodopsin - metarhodopsin - transducin - an enzyme that hydrolyzes cGMP. As a result of this cascade, a closing membrane is formed on the external receptor, which is associated with cGMP and is responsible for the operation of the cation channel.

In the dark, cations (mainly sodium ions) penetrate through open channels, which lead to partial depolarization of the photoreceptor cell. At the same time, this photoreceptor releases a mediator (amino acid glutamate), which affects the inaptic endings of second-order neurons. Upon slight light stimulation, the rhodopsin molecule isomerizes into the active form. This leads to the closure of the transmembrane ion channel, and, accordingly, stops the cation flow. As a result, the photoreceptor cell hyperpolarizes, and mediators cease to be released in the zone of contact with second-order neurons.

In the dark, sodium ions (80%), calcium (15%), magnesium and other cations flow through transmembrane channels. To remove excess calcium and sodium during darkness, a cation exchanger operates in the photoreceptor cells. It was previously believed that calcium is involved in the photoisomeration of rhodopsin. However, there is now evidence that this ion plays other roles in phototransduction. Due to the presence of a sufficient concentration of calcium, rod photoreceptors become more receptive to light, and the recovery of these cells after illumination is significantly increased.

Cone photoreceptors are able to adapt to light levels, so the human eye is able to perceive objects in different lighting conditions (ranging from shadows under a tree to objects located on shiny, illuminated snow). Rod photoreceptors have less adaptability to light levels (7-9 units and 2 units for cones and rods, respectively).

Photopigments of exteroceptors of cones and rods of the retina

Photopigments of the cone and rod apparatus of the eye include:

• Iodopsin;
• Rhodopsin;
• Cyanolab.

All these pigments differ from each other in the amino acids that make up the molecule. In this regard, pigments absorb a certain wavelength, or rather a range of wavelengths.

Cone exteroceptor photopigments

The cones of the retina contain iodopsin and a type of iodopsin (cyanolab). All distinguish three types of iodopsin, which are tuned to wavelengths of 560 nm (red), 530 nm (green) and 420 nm (blue).

On the existence and identification of cyanolabe

Cyanolab is a type of iodopsin. In the retina of the eye, blue cones are located regularly in the peripheral zone, green and red cones are localized randomly over the entire surface of the retina. At the same time, the density of distribution of cones with green pigments is greater than that of red ones. The lowest density is observed in blue cones.

The following facts support the theory of trichromasia:

• The spectral sensitivity of the two cone pigments was determined using densitometry.
• Three pigments of the cone apparatus have been identified using microspectrometry.
• The genetic code responsible for the synthesis of red, blue and green cones has been identified.
• Scientists were able to isolate cones and measure their physiological response to irradiation with light of a specific wavelength.

The theory of trochromasia was previously unable to explain the presence of four primary colors (blue, yellow, red, green). It was also difficult to explain why dichromatic people were able to distinguish between white and yellow. Currently, a new retinal photoreceptor has been discovered, in which melanopsin plays the role of pigment. This discovery put everything in place and helped answer many questions.

Recent studies have also examined sections of avian retinas using a fluorescence microscope. In this case, four types of cones were identified (violet, green, red and blue). Due to opponent color vision, photoreceptors and neurons complement each other.

Rod photopigment rhodopsin

Rhodopsin belongs to the family of G-linked proteins, which is so named because of its transmembrane signal transduction mechanism. In this case, G-proteins located in the near-membrane space are involved in the process. When studying rhodopsin, the structure of this pigment was established. This discovery is very important for biology and medicine, because rhodopsin is the ancestor of the GPCR receptor family. In this regard, its structure is used in the study of all other receptors, and also determines functionality. Rhodopsin is named so because it has a bright red color (from Greek it literally translates as pink vision).

Day and night vision

By studying the absorption spectra of rhodopsin, it can be seen that reduced rhodopsin is responsible for the perception of light in low light conditions. In daylight, this pigment decomposes, and the maximum sensitivity of rhodopsin shifts to the blue spectral region. This phenomenon is called the Purkinje effect.

In bright light, the rod ceases to perceive daylight rays, and the cone takes on this role. In this case, photoreceptors are excited in three regions of the spectrum (blue, green, red). These signals are then converted and sent to the central structures of the brain. As a result, a color optical image is formed. It takes about half an hour for rhodopsin to fully recover under low light conditions. During this entire time, there is an improvement in twilight vision, which reaches a maximum at the end of the period of pigment restoration.

Biochemist M.A. Ostrovsky conducted a series of fundamental studies and showed that rods containing the pigment rhodopsin are involved in the perception of objects in low light conditions and are responsible for night vision, which is black and white.

Vitamin deficiency is expressed on the face. In addition to peeling skin, it leads to brittle hair and nails. These are symptoms that are easy to notice from the outside. Well, what's going on inside?

Internal organs also suffer noticeably from a lack of vitamins. The eyes are particularly damaged. These sensitive organs react painfully to any changes in the body. Why is vitamin deficiency dangerous for the eyes? Why does it occur? How to avoid it?

Consequences of ocular vitamin deficiency

If there is a deficiency of vitamins and minerals needed by the eyes, visual acuity may decrease. A common side effect of vitamin deficiency is night blindness. This illness is expressed in the deterioration of gloomy vision. Poor lighting may reduce your field of vision.

Typical signs of vitamin deficiency in the eyes include a feeling of sand in the eyes, redness and tearfulness. All this may be accompanied by pain.

The pathologies present are aggravated by vitamin deficiency. This condition is especially dangerous for glaucoma sufferers. Under the influence of this disease, the nutrition of the internal media of the eye is disrupted. Vitamin deficiency aggravates the situation. This can lead to progression of optic nerve atrophy. Blindness moves a few steps closer.

Why does vitamin deficiency occur?

Usually the cause of vitamin deficiency is seasonality. At the end of autumn, throughout winter and at the beginning of spring, a person’s diet may differ from summer. Due to the rise in prices of vegetables and fruits, many people practically exclude them from their diet. Weather conditions prevent the body from producing vitamins. The lack of sufficient sunlight and heat slows down this process. In addition, bad weather encourages most to be content with home leisure. Lifestyle becomes more passive. Along with it, the production of vitamins slows down.

But this is not the only compelling reason. Some people eat well and lead a healthy lifestyle, but still suffer from vitamin deficiencies.

This situation can occur while taking antibiotics and some other drugs.

Replenishment with vitamins

To ensure yourself good vision in any weather, you should feed your eyes with the necessary set of vitamins. What vitamins are required? Where to eat them?

Vitamin A / retinol / provitamin A / carotene

It is also called the vitamin of vision. It is part of the visual pigment of the retina (riboxin). This substance is also found in the visual pigment of cones (rhodopsin). These organs are necessary to perceive the light impulse and transmit it to the brain. Therefore, to maintain good vision, the body needs vitamin A. It is included in a number of delicious foods:

• Sorrel;
• Spinach;
• Carrot.
• Butter;
• Egg yolk;
• Cod liver;
• Fish oil.

B vitamins

They are necessary for the normal functioning of the nervous system and the tone of body tissues. These vitamins are found in:

• Green vegetables and fruits;
• Liver;
• Kidneys;
• Heart;
• Dairy products;
• Eggs.

Riboflavin/B2

Deficiency of this substance leads to inflammation of the mucous membrane of the eye. The result is a sensation of a foreign body in the eye, pain and lacrimation. In some cases, there is difficulty focusing the eye. This vitamin is found in:

Nicotinic acid / vitamin PP

This substance belongs to the B vitamins. It is worth highlighting separately, since it plays a vital role in the metabolic processes of the body. Vitamin PP is necessary for the redox process. This substance plays an important role in cellular metabolism. It maintains the normal functioning of blood vessels and prevents the formation of cholesterol.

You can get enough of this vitamin by pouring legumes into a plate.

This component strengthens the immune system. Thanks to it, rapid restoration and healing of cells occurs, strengthening the walls of blood vessels. It also protects the body from infections. Vitamin C prevents the development of cataracts. You can get it by eating fresh vegetables, fruits, berries and herbs.

Many experts believe that vitamin D deficiency contributes to the development of myopia. The fact is that this component is involved in the transport and absorption of calcium. It is necessary for bone strength and muscle tone. The quality of the properties of the lens directly depends on the work of the eye muscles. Actually, do not neglect foods that contain vitamin D:

• Herring;
• Salmon;
• Liver of animals and birds;
• Eggs;
• Dairy products.

Try to take frequent walks in the sun, but don't overheat.

Lutein, zeaxanthin

These antioxidants protect cells from the negative effects of radicals. In particular, they are necessary to prevent cataracts, glaucoma and conjunctivitis. They prevent the development of age-related macular degeneration.

• Fresh vegetables and fruits (especially orange and yellow flowers);
• Blueberries;
• Seaweed;
• Egg yolk.

source

The lack of vitamins in human food leads to metabolic disorders, since vitamins are involved in the formation

Vitamins are an integral part of enzymes.

Vitamins in the human and animal body

1) regulate the supply of oxygen

2) influence growth, development, metabolism

3) cause the formation of antibodies

4) increase the rate of formation and breakdown of oxyhemoglobin

Vitamins are an integral part of enzymes, so they participate in all reactions of the body and influence growth, development and metabolism.

Rye bread is a source of vitamin

Rye bread contains B vitamins.

Vitamin is synthesized in human skin under the influence of ultraviolet rays

Vitamin D is synthesized under the influence of UV rays.

1) destroys poisons secreted by microbes

2) destroys poisons secreted by viruses

3) protects enzymes responsible for antibody synthesis from oxidation

4) is a component of antibodies

Antibodies are proteins; vitamins cannot destroy poisons.

What vitamin is part of the visual pigment contained in the light-sensitive cells of the retina?

What vitamin should be included in the diet of a person with scurvy?

Scurvy develops due to a lack of vitamin C.

What role do vitamins play in the human body?

1) are a source of energy

2) perform a plastic function

3) serve as components of enzymes

4) affect the speed of blood movement

Vitamins are components of enzymes, the source of energy is glucose, and the plastic function is performed by amino acids, forming proteins.

Vitamin A deficiency in humans leads to disease

Diabetes mellitus develops due to a lack of the hormone insulin, scurvy due to a lack of vitamin C, rickets due to a lack of D.

Fish oil contains a lot of vitamins:

Fish oil contains vitamin D, which is necessary for the growth and development of the musculoskeletal system.

Lack of vitamin A in the human body leads to disease

In light-sensitive cells, the visual pigment contains vitamin A, and if it is deficient, the disease Night Blindness develops.

Lack of vitamin C in the human body leads to disease

1 – with a lack of vitamin A, 2 – with a lack of insulin, 4 – with a lack of vitamin D.

A lack of vitamin C in the human body leads to scurvy.

Lack of vitamin D in the human body leads to disease

A – with a lack of vitamin A, B – with a lack of insulin, C – with a lack of vitamin C.

Consuming foods or special medications containing vitamin D

4) increases hemoglobin content

2 - ensures normal growth and development of skeletal bones; Prevents the development of rickets in childhood.

1 - proteins; 3 - vitamin A; 4 - vitamin B12 and iron.

Source: Unified State Examination in Biology 05/05/2014. Early wave. Option 1.

B vitamins are synthesized by symbiont bacteria in

B vitamins are synthesized by symbiont bacteria in the large intestine.

The role of B vitamins is global. These low molecular weight organic compounds are involved in a huge number of processes: from the release of energy from carbohydrates to the synthesis of antibodies and regulation of the nervous system. Despite the fact that B vitamins are present in many foods, it is thanks to their synthesis by the intestinal microflora that the body receives the amount of these vitamins that is necessary for normal human life.

Source: Unified State Exam in Biology 04/09/2016. Early wave

Vitamins are bioorganic low-molecular compounds that are necessary for normal metabolism in all organs and tissues of the human body. Vitamins enter the human body from the outside and are not synthesized in the cells of its organs. Most often, vitamins are synthesized by plants, less often by microorganisms. That is why a person should regularly eat fresh plant foods, such as vegetables, fruits, grains, herbs, etc. The source of vitamins synthesized by microorganisms are

intestines. Thus, the importance of the normal composition of microflora

Depending on the structure and functions, each bioorganic compound is a separate vitamin, which has a traditional name and designation in the form of a letter of the Cyrillic or Latin alphabet. For example, the vitamin is designated by the letter D and has the traditional name cholecalciferol. In medical and popular scientific literature, both options can be used - both the designation and the traditional name of the vitamin, which are synonyms. Each vitamin performs certain physiological functions in the body, and its deficiency causes various disturbances in the functioning of organs and systems. Let's look at various aspects regarding vitamin A.

What vitamins are meant under the general designation “vitamin A”?

Vitamin A is the common name for three bioorganic compounds belonging to the group of retinoids. That is, vitamin A is a group of the following four chemicals:

All of these substances are different forms of vitamin A. Therefore, when they talk about vitamin A, they mean either any of the substances listed above, or all of them together. The general name for all forms of vitamin A is retinol, which we will use in the rest of the article.

However, in the instructions for dietary supplements (dietary supplements), manufacturers describe in detail which chemical compound is included in their composition, not limiting themselves to simply mentioning “vitamin A.” This is usually due to the fact that manufacturers indicate the name of the compound, for example, retinoic acid, and then describe in great detail all its physiological effects and positive effects on the human body.

In principle, different forms of vitamin A perform different functions in the human body. Thus, retinol and dehydroretinol are necessary for the growth and formation of normal structures of any tissue and the proper functioning of the genital organs. Retinoic acid is necessary for the formation of normal epithelium. Retinal is necessary for the normal functioning of the retina, as it is part of the visual pigment rhodopsin. However, usually all these functions are not divided by form, but are described together, as inherent in vitamin A. In the following text, in order to avoid confusion, we will also describe the functions of all forms of vitamin A, without separating them. We will indicate that a certain function is inherent in a certain form of vitamin A only if necessary.

General characteristics of vitamin A

Vitamin A is fat-soluble, that is, it dissolves well in fats, and therefore easily accumulates in the human body. It is precisely because of the possibility of accumulation that fat-soluble vitamins, including A, can cause an overdose when used for a long time in large quantities (more than 180 - 430 mcg per day, depending on age). An overdose, as well as a deficiency of vitamin A, leads to serious disruptions in the normal functioning of various organs and systems, primarily the eyes and reproductive tract.

Vitamin A exists in two main forms:1. Vitamin A itself ( retinol), contained in products of animal origin;

carotene), found in foods of plant origin.

Retinol from animal products is immediately absorbed by the human body in the digestive tract. And carotene (provitamin A), entering the intestines, first turns into retinol, after which it is absorbed by the body.

After entering the intestines, from 50 to 90% of the total amount of retinol is absorbed into the blood. In the blood, retinol combines with proteins and in this form is transported to the liver, where it is stored in reserve, forming a depot, which, if the supply of vitamin A from the outside ceases, can last for at least a year. If necessary, retinol from the liver enters the blood and, along with its current, enters various organs, where cells, with the help of special receptors, capture the vitamin, transport it inside and use it for their needs. Retinol is constantly released from the liver, maintaining its normal concentration in the blood of 0.7 µmol/l. When vitamin A is taken from food, it first goes to the liver, replenishing spent reserves, and the remaining amount remains to circulate in the blood. Retinal and retinoic acid in the blood are contained in trace amounts (less than 0.35 µmol/l), since in this form vitamin A is present mainly in the tissues of various organs.

Getting into the cells of various organs, retinol is converted into its active forms - retinal or retinoic acid, and in this form is integrated into various enzymes and other biological structures that perform vital functions. Without active forms of vitamin A, these biological structures are not able to perform their physiological functions, as a result of which various disorders and diseases develop.

Vitamin A enhances its effect and is better absorbed in combination with vitamin E and the trace element zinc.

Biological functions of vitamin A (role in the body) Vitamin A in the human body performs the following biological functions:

• Improve the growth and development of cells of all organs and tissues;
• Essential for normal growth and bone formation;
• Necessary for the normal functioning of all mucous membranes and skin epithelium, as it prevents hyperkeratosis, excessive desquamation and metaplasia (cancerous degeneration of epithelial cells);
• Provide good vision in low or low light conditions (so-called twilight vision). The fact is that retinol is part of the visual pigment rhodopsin, located in the cells of the retina, called rods for their specific shape. It is the presence of rhodopsin that ensures good visibility in conditions of low, not bright lighting;
• Improves the condition of hair, teeth and gums;
• Improves the growth of the embryo, promotes the proper formation and development of various organs and tissues of the fetus;
• Strengthens the formation of glycogen in the liver and muscles;
• Increases the concentration of cholesterol in the blood;
• Takes part in the synthesis of steroid hormones (testosterone, estrogens, progesterone, etc.);
• Prevents the development of malignant tumors of various organs;
• Regulates immunity. Vitamin A is necessary for the complete process of phagocytosis. In addition, retinol enhances the synthesis of immunoglobulins (antibodies) of all classes, as well as T-killers and T-helpers;
• Antioxidant. Vitamin A has powerful antioxidant properties.

The list lists the effects of vitamin A at the organ and tissue level. At the cellular level of biochemical reactions, vitamin A has the following effects:1. Activation of the following substances:

• Chondroitinsulfuric acid (component of connective tissue);
• Sulfoglycans (components of cartilage, bones and connective tissue);
• Hyaluronic acid (the main substance of intercellular fluid);
• Heparin (thins the blood, reduces its coagulability and thrombus formation);
• Taurine (stimulator of growth hormone synthesis, as well as a necessary link in the transmission of nerve impulses from neurons to organ tissues);
• Liver enzymes that ensure the transformation of various exogenous and endogenous substances;

2. Synthesis of special substances called class A somaticidenes

B and C, which enhance and improve the formation of muscle proteins and collagen;

3. Synthesis of female and male sex hormones;

4. Synthesis of substances necessary for the functioning of the immune system, such as lysozyme, immunoglobulin A and

5. Synthesis of epithelial enzymes, which prevent premature keratinization and desquamation;

6. Activation of receptors for vitamin D;

7. Ensuring timely inhibition of cell growth, which is necessary for the prevention of malignant tumors;

8. Ensuring the completion of phagocytosis (destruction of the pathogenic microbe);

9. Formation of the visual pigment - rhodopsin, which ensures normal vision in low light conditions.

As you can see, vitamin A, in addition to ensuring good vision, has a fairly wide range of different effects in the human body. However, vitamin A has traditionally been associated only with effects on the eyes. This is due to the fact that the role of vitamin A specifically for vision was studied earlier than all others, and this was done in great detail, while other effects and functions were identified later. In this regard, the idea has been established that vitamin A is a substance necessary for normal vision, which, in principle, corresponds to reality, but does not fully reflect it, since in fact retinol also performs other, no less important functions. functions.

Daily requirement of vitamin A for people of different ages

A person at different ages should consume different amounts of vitamin A per day. The daily intake of vitamin A for children of different ages, regardless of gender, is as follows:

• Newborns up to six months – 400 – 600 mcg;
• Children from 7 to 12 months – 500 – 600 mcg;
• Children from 1 to 3 years – 300 – 600 mcg;
• Children from 4 to 8 years old – 400 – 900 mcg;
• Children 9 – 13 years old – 600 – 1700 mcg.

Starting from the age of 14, vitamin A intake standards for women and men differ, which is due to the peculiarities of the functioning of organisms. The daily norms of vitamin A for men and women of different ages are presented in the table.

The table and list show two numbers, the first of which means the optimal amount of vitamin A a person needs per day. The second number indicates the maximum allowable amount of vitamin A per day. According to the recommendations of the World Health Organization, only 25% of the daily requirement for vitamin A should be provided from plant foods. The remaining 75% of the daily requirement for vitamin A should be provided by animal products.

Insufficient intake of vitamin A leads to its deficiency, which is manifested by a number of disorders in various organs. However, excess intake of the vitamin into the body can also provoke serious health disorders caused by excess or hypervitaminosis A. Hypervitaminosis A is possible due to the fact that retinol is able to accumulate in tissues and is slowly excreted from the body. Therefore, vitamin A should not be consumed in large quantities, believing that nothing bad will come from such a beneficial substance. You should adhere to the recommended doses of vitamin A and not exceed the maximum permissible daily dosage.

What foods contain vitamin A?

Vitamin A in the form of retinol is found in the following animal products:

• Chicken, beef and pork liver;
• Canned cod liver;
• Beluga caviar is granular;
• Egg yolk;
• Butter;
• Hard varieties of cheese;
• Fatty meats and fish.

Vitamin A is found in the form of carotenoids in the following plant foods:

• Carrot;
• Parsley;
• Celery;
• Spinach;
• Cheremsha;
• Rose hip;
• Red bell pepper;
• Bow-feather;
• Salad;
• Apricots;
• Pumpkin;
• Tomatoes.

To clearly and quickly understand whether a given plant contains vitamin A, you can use a simple rule - carotenes are found in all red-orange vegetables and fruits. Therefore, if a vegetable or fruit is painted such a bright orange color, then it definitely contains vitamin A in the form of carotenoids.
Vitamin A content in various foods, need for vitamin A - video

Symptoms of vitamin A deficiency and hypervitaminosis

Vitamin A deficiency in the body leads to the development of the following clinical manifestations:

• Dry skin;
• Hyperkeratosis on the knees and elbows (severe peeling and dry skin);
• Follicular hyperkeratosis (toad skin syndrome);
• Acne;
• Pustules on the skin;
• Dry and dull hair;
• Brittle and striated nails;
• Twilight vision disorder (night blindness);
• Blepharitis;
• Xerophthalmia;
• Perforation of the cornea of ​​the eye with subsequent blindness;
• Deterioration in the activity of the immune system;
• Tendency to frequent infectious diseases;
• Weakened erection in men;
• Low sperm quality;
• Increased risk of malignant tumors.

Hypervitaminosis A can be acute or chronic. Acute hypervitaminosis develops with the simultaneous intake of large amounts of vitamin A. Most often, acute hypervitaminosis A is observed when eating the liver of polar animals, which contains a lot of retinol. Due to the excessive amount of vitamin A, residents of the Far North (Eskimos, Khanty, Mansi, Kamchadals, etc.) have a taboo on eating the liver of polar mammals. Acute hypervitaminosis A is manifested by the following symptoms that occur after consuming large amounts of retinol:

• Pain in the abdomen, bones and joints;
• General weakness;
• Malaise;
• Sweating at night;
• Headache associated with nausea and vomiting;
• Hair loss;
• Menstrual irregularities;
• Disorders of the digestive tract;
• Cracks in the corners of the mouth;
• Irritability;
• Brittle nails;
• Itching all over the body.

Chronic hypervitaminosis A is more common than acute hypervitaminosis and is associated with long-term use of retinol in doses slightly exceeding the maximum permissible. Clinical manifestations of chronic hypervitaminosis A are as follows:

• Itching and redness of the skin;
• Peeling of the skin on the palms, soles and other areas;
• Dandruff;
• Hair loss;
• Pain and swelling of soft tissues located along the long bones of the body (femur, lower leg, shoulder, forearm, fingers, ribs, collarbone, etc.);
• Calcification of ligaments;
• Headache;
• Irritability;
• Excitation;
• Confusion;
• Double vision;
• Drowsiness;
• Insomnia;
• Hydrocephalus in newborns;
• Increased intracranial pressure;
• Bleeding gums;
• Mouth ulcers;
• Nausea and vomiting;
• Diarrhea;
• Enlarged liver and spleen;
• Pseudojaundice.

The severity of symptoms of chronic hypervitaminosis varies depending on the concentration of vitamin A in the blood.

If a pregnant woman consumes vitamin A in dosages above 5000 IU (1500 mcg) daily for a long time, this can cause fetal growth retardation and abnormal development of the urinary tract. Vitamin A intake during pregnancy at a dose of more than 4,000 mcg (13,400 IU) can lead to congenital malformations in the fetus.

Vitamin A: benefits, symptoms of deficiency, contraindications and signs of overdose - video

Use of vitamin A

The most common use of vitamin A is in

Therapy of skin diseases, as well as in the treatment of vascular diseases. In recent years, vitamin A has been widely used

Andrologists and reproductive specialists in comprehensive treatment programs

and preparation for pregnancy. However, the complex scope of application of this vitamin is much wider.

Thus, vitamin A improves the growth and development of various organs and tissues, so it is recommended to be given to children to normalize the process of formation of bones, muscles and ligaments. In addition, retinol ensures the normal functioning of the reproductive process, so the vitamin is successfully used during pregnancy, during puberty and in women or men of reproductive age in order to improve the functioning of the reproductive system.

Vitamin A during pregnancy promotes normal fetal growth, preventing developmental delays. In adolescents, vitamin A normalizes the development and formation of the genital organs, and also helps regulate reproductive functions (maintains sperm quality, normal menstrual cycle, etc.), optimally preparing the bodies of girls and boys for future childbearing. In adults, vitamin A ensures optimal functioning of the reproductive organs, which significantly increases the chances of conceiving, bearing and giving birth to a healthy baby. The most pronounced positive effect of vitamin A on reproductive function is observed when it is used in combination with vitamin E. Therefore, vitamins A and E are considered the key to the normal ability of men and women to bear children.

The function of vitamin A in ensuring good vision in low light conditions is widely known. With a lack of vitamin A, a person develops night blindness - a visual impairment in which he sees poorly at dusk or in low light. Regular intake of vitamin A is an effective method of preventing night blindness and other visual impairments.

Also, vitamin A in people of any age and gender ensures the normal functioning of the skin and mucous membranes of various organs, increasing their resistance to infectious diseases. It is precisely because of its huge role in maintaining the normal structure and functions of the skin that it is called the “beauty vitamin.” Due to its positive effect on skin, hair and nails, vitamin A is often included in various cosmetic preparations - creams, masks, shower gels, shampoos, etc. Retinol also plays a role as a beauty vitamin because of its ability to reduce the rate of aging, maintaining the natural youth of women and men. In addition, retinoic acid is successfully used in the treatment of inflammatory and wound diseases of the skin, such as psoriasis, acne, leukoplakia, eczema, lichen, prurigo, pyoderma, furunculosis, urticaria, premature graying of hair, etc. Vitamin A accelerates the healing of wounds and sunburn burns, and also reduces the risk of infection of wound surfaces.

Since vitamin A increases the resistance of mucous membranes to infections, its regular use prevents colds of the respiratory tract and inflammatory processes in the digestive tract and genitourinary system. Vitamin A is used in the complex treatment of intestinal erosions and ulcers, chronic gastritis, gastric ulcers, hepatitis, liver cirrhosis, tracheitis, bronchitis and nasopharyngeal catarrh.

The antioxidant properties of vitamin A determine its ability to destroy cancer cells, preventing the development of malignant neoplasms of various organs. Vitamin A has a particularly strong preventive anti-oncogenic effect against pancreatic and breast cancer. Therefore, vitamin A is used in the practice of oncologists as part of complex treatment and prevention of relapses of various tumors.

As an antioxidant, vitamin A increases the content of high-density lipoprotein (HDL) in the blood, which is very important for the prevention of cardiovascular diseases such as hypertension, coronary artery disease, heart attacks, etc. Therefore, large doses of vitamin A are currently used to treat vascular diseases.

Vitamins A for pregnant women

Vitamin A is very important for the normal course of

and proper and complete development of the fetus. From the point of view of a pregnant woman, vitamin A has the following positive effects on her body:

• Improves immunity, which prevents colds and other infectious and inflammatory diseases to which pregnant women are susceptible;
• Reduces the risk of developing infectious and inflammatory diseases of the respiratory system, digestive tract and genitourinary system, thereby preventing numerous relapses of thrush, bronchitis, rhinitis and other pathologies that often develop in pregnant women;
• Maintains normal skin condition, preventing the appearance of stretch marks (striae);
• Maintains the normal condition of hair and nails, preventing their loss, fragility and dullness;
• Helps ensure normal growth of the uterus;
• Maintains normal vision in pregnant women and also prevents its deterioration;
• Supports continuation of pregnancy, preventing premature birth.

The listed effects of vitamin A have a beneficial effect on the general well-being of a pregnant woman, and, consequently, increase her quality of life and the likelihood of a favorable outcome. In addition, vitamin A relieves women from common problems associated with pregnancy, such as dull and falling hair, dry and

Cracked and peeling nails, stretch marks, permanent

and vaginal thrush, etc.

Taking vitamin A by a pregnant woman has the following positive effects on the fetus:

• Improves the growth and development of the fetal skeletal system;
• Normalizes fetal growth;
• Prevents fetal development delay;
• Ensures normal formation of the genitourinary tract organs in the fetus;
• Prevents fetal hydrocephalus;
• Prevents fetal malformations;
• Prevents premature birth or miscarriage;
• Prevents infection with various infections that can penetrate the placenta.

Thus, vitamin A has a positive effect on both the pregnant woman and the fetus, so its use in therapeutic dosages is justified.

However, since an excess of vitamin A can negatively affect the course of pregnancy, causing miscarriages and delays in fetal development, it should only be taken under the supervision of a doctor, strictly following the prescribed dosages. The optimal daily dosage of vitamin A for a pregnant woman is no more than 5000 IU (1500 mcg or 1.5 mg).

Currently, in the countries of the former USSR, gynecologists often prescribe to pregnant women and women planning pregnancy the complex drug “Aevit”, which simultaneously contains vitamins A and E. Aevit is prescribed precisely because of the positive effects of vitamins A and E on reproductive function. However, this drug should not be taken by pregnant women or women planning pregnancy, since it contains a huge dose of vitamin A (100,000 IU), which exceeds the optimal and recommended by WHO by 20 times! Therefore, Aevit is dangerous for pregnant women, as it can cause miscarriages, malformations and other disorders in the fetus.

Pregnant women, without harm to the fetus, can take complex preparations that contain no more than 5000 IU of vitamin A, for example, Vitrum, Elevit, etc. However, since vitamin A is not a completely harmless drug, it is recommended to do a blood test for the content of this substance before using it . Then, based on the concentration of vitamin A, determine the individual dosage that is optimal for a given pregnant woman.

Vitamin A is very important for normal growth and development of the musculoskeletal system in children. That is why it is recommended to give it to children during periods of intensive growth, when the supply of vitamin from food may not meet the increased needs of the body. In addition, vitamin A is very important for the proper formation of reproductive organs during periods

Both boys and girls. In girls, vitamin A promotes the rapid establishment of a normal menstrual cycle and the formation of resistance of the vaginal mucosa to various infections. In boys, vitamin A contributes to the formation of normal erections and the development of testicles with the formation of good quality sperm necessary for future conception.

In addition, by increasing the resistance of mucous membranes to various pathogenic microorganisms, vitamin A prevents frequent infectious and inflammatory diseases of the respiratory organs in children. Vitamin A also supports normal vision in a child. In adolescents, vitamin A can reduce the number of acne and pimples, which has a positive effect on the child’s quality of life.

It is precisely because of the pronounced positive effect on the body that it is recommended to give the child vitamin A in preventive dosages of 3300 IU per day in short, periodically repeated courses. To do this, it is recommended to purchase either multivitamin preparations or special vitamin tablets with a preventive dosage of 3300 IU.

Preparations containing vitamin A Currently, the following dosage forms are used as preparations containing vitamin A:

1. Natural plant extracts (included in dietary supplements).

2. Synthetic vitamins that completely imitate the structure of natural chemical compounds (included in one-component vitamin preparations and multivitamins).

Pharmacological preparations containing synthetic vitamin A include the following:

• Retinol acetate or retinol palmitate – tablets containing 30 mg (30,000 mcg or 100,000 IU of retinol);
• Retinol acetate or retinol palmitate – dragees containing 1 mg (1000 mcg or 3300 IU of retinol);
• Axeromalt – vitamin A concentrate in fish oil (1 ml of fat contains 100,000 or 170,000 IU of retinol) in bottles;
• Oil solution of carotene;
• Aevit;
• Alphabet;
• Biovital-gel;
• Biorhythm;
• Vita Bears;
• Vitasharm;
• Vitrum;
• Duovit;
• Complivit;
• Multi-Tabs baby and classic;
• Multifort;
• Pikovit;
• Polivit baby and classic;
• Sana-Sol;
• Supradin;
• Centrum.

An oil solution of carotene is used externally in the form of dressings and lotions. The solution is applied to chronic eczema, long-term and poorly healing ulcers, burns, frostbite and other skin wounds.

Tablets containing 30 mg of retinol and Aevit are used only for medicinal purposes, for example, to eliminate vitamin A deficiency or treat vascular and skin diseases. These tablets and Aevit cannot be used for prophylactic purposes in people of any age, since this can provoke hypervitaminosis, as well as hypovitaminosis, which manifests itself in severe dysfunction of various organs and systems. All other drugs are vitamins used to prevent hypovitaminosis. Accordingly, they can be given to people of any age, including children and pregnant women.

Dietary supplements containing vitamin A in the form of natural extracts and extracts include the following:

• ABC Spectrum;
• Antioxidant capsules and dragees;
• Arthromax;
• Viardot and Viardot forte;
• Wheat germ oil;
• Methovit;
• Will direct;
• Nutricap;
• Oxylic;
• Blueberry forte.

All of the listed dietary supplements contain a preventive dosage of vitamin A, so they can be used in periodic short courses in people of different ages.
Vitamin A in the vitamin complex

Vitamin A is currently included in many complex preparations. Moreover, the absorption of vitamin A from complex preparations is no worse than from monocomponent preparations. However, the use of multivitamins is very convenient for a person, since it allows him to take only one tablet. Complex multivitamins contain various vitamin compounds in the required preventive dosage, which is also very convenient for use. However, these drugs contain different dosages of vitamin A, so when choosing a specific multivitamin, it is necessary to take into account the age and general condition of the person who will take it.

For example, the following complex preparations containing vitamin A are recommended for children of different ages and adults:

• Children under one year old – Multi-Tabs Baby, Polivit Baby;
• Children from 1 to 3 years old – Sana-Sol, Biovital-gel, Pikovit, Alphabet “Our Baby”;
• Children from 3 to 12 years old – Multi-Tabs classic, Vita Bears, Alphabet “Kindergarten”;
• Children over 12 years old and adults - Vitrum, Centrum and any dietary supplements (dietary supplements).

The best vitamins A The best vitamins A do not exist, since each pharmaceutical drug or dietary supplement has a range of indications and its own dosage of retinol. In addition, each drug has an optimal effect for specific, individual disorders or for the prevention of strictly defined diseases and conditions. Therefore, in the treatment of one disease, the best would be, for example, a vitamin A preparation called “Aevit”; for another pathology, Centrum vitamins, etc. Thus, for each case, a different drug containing vitamin A will be best. That is why in medicine there is no concept of “best” drug, but only the definition of “optimal”, which can be different in each specific case.

However, it is possible to very roughly identify the “best” vitamin A for various conditions. So, relatively speaking, for the prevention of hypovitaminosis A in children, men, women and pregnant women, various multivitamin complexes will be the best. To eliminate an existing deficiency of vitamin A or a general strengthening effect on the body, the best would be single-component tablets or dragees containing at least 5000 IU of retinol acetate or palmitate. For the treatment of vascular diseases, inflammatory processes on the mucous membranes of the respiratory, digestive and genitourinary organs, as well as infectious-inflammatory, wound and ulcerative lesions of the skin, the best are monocomponent preparations containing at least 100,000 IU of vitamin A (for example, Aevit, fish oil concentrate etc.). For the treatment of wounds on the skin and mucous membranes, the best option would be an external vitamin A preparation - an oil solution of carotene.

Vitamin A - instructions for use

Any vitamin A preparations can be taken orally in the form of tablets, dragees, powders and solutions, injected intramuscularly or used externally in the form of applications, bandages, lotions, etc. Intramuscular administration of vitamin A is used only in hospital settings in the treatment of severe vitamin deficiency, severe night blindness, as well as severe inflammatory diseases of the digestive tract, genitourinary and respiratory organs. Vitamin A is used externally in the form of an oil solution to treat ulcers, inflammations, wounds, eczema,

Burns and other skin lesions. Vitamin A is taken internally for preventive purposes and for the treatment of mild hypovitaminosis.

You should take 3 to 5 tablets or pills orally per day after meals. An oil solution of vitamin A is taken 10–20 drops three times a day after meals on a piece of black bread. The duration of the course of use ranges from 2 weeks to 4 months and depends on the purpose for which vitamin A is used. For the treatment of hypovitaminosis, night blindness, as well as the prevention of inflammatory diseases of the skin and mucous membranes, general strengthening of the immune system and maintaining normal concentrations of vitamin in the body, long-term courses for at least one month. After taking vitamin A for a month, you need to take a break for 2 to 3 months, after which the course can be repeated.

An intramuscular solution of vitamin A is administered every other day to adults at 10,000–100,000 IU and to children at 5,000–10,000 IU. The course of treatment is 20–30 injections.

The maximum permissible single dosage of vitamin A for oral and intramuscular administration is 50,000 IU (15,000 mcg or 15 mg), and the daily dosage is 100,000 IU (30,000 mcg or 30 mg).

Locally, an oil solution of vitamin A is used to treat various wounds and skin inflammations (ulcers, frostbite, burns, non-healing wounds, eczema, boils, pustules, etc.), applying it to a previously cleaned affected surface. The wound surface is simply lubricated with an oil solution of 5 - 6 times a day and cover with 1 – 2 layers of sterile gauze. If the wound cannot be left open, then ointment with vitamin A is applied to it and a sterile bandage is placed on top. When using vitamin A topically, it is necessary to prescribe it orally in prophylactic dosages (5000 - 10,000 IU per day).

Better absorption and enhanced therapeutic and biological effects of vitamin A are facilitated by vitamin E. Therefore, when prescribing vitamin A, it is recommended to supplement it with vitamin E. Vitamin A should not be used simultaneously with Cholestyramine and sorbents (for example, activated carbon, Enterodes, Polyphepan, etc.), since these drugs interfere with its absorption.

ATTENTION! The information posted on our website is for reference or popular information and is provided to a wide range of readers for discussion. Prescription of medications should be carried out only by a qualified specialist, based on the medical history and diagnostic results.

Vitamin A was the first vitamin discovered to the world. If previously it was believed that its use could improve vision, now new properties of retinol have been discovered, thanks to which it is possible to prevent diseases such as cancer tumors, vascular lesions, diabetes mellitus, and viral infections. Retinol is called the vitamin of youth and beauty. It is included in many well-known cosmetics and is prescribed to avoid premature aging and maintain sexual activity.

Vitamin A is a group of compounds collectively called retinoids. These substances are similar in structure and biological functions. These include:

• Retinol acetate is vitamin A1, its active form is retinal.
• Dehydroretinol – vitamin A2
• Retinoic acid.

These compounds are found only in animal products. Plants contain provitamin A, called carotene. There are about 500 varieties of plant carotenoids. The most famous:

In the liver and intestines, carotenoids are converted into vitamin A. This vitamin, as well as all its derivatives, are highly soluble in oil and poorly soluble in water.

Retinol formula is C20H30O.

The different forms of vitamin A have similar actions, but have specific features listed below.

• Retinol and dihydroretinol are responsible for the growth processes in children and the proper functioning of the genital organs.
• Retinoic acid has a stimulating effect on the epithelium.
• Retinal is part of the visual pigment - rhodopsin.

Vitamin A was discovered in 1913 by scientists who studied the effects of chicken egg yolk and butter on the body. Two groups, McCollut and Osborne and their colleagues, independently concluded that these products contain a fat-soluble substance that is necessary for the growth of animals. It was called “A factor”, which was renamed vitamin A by Drummond in 1916. In 1921, Steenbock described vitamin A deficiency with signs of growth retardation, a tendency to infectious diseases and eye damage.

Vitamin A1 is called retinol or axerophthol; in its pure form it is unstable, so retinol palmitate or retinol acetate is used for use.

Vitamin A2 differs from retinol by an additional double bond in the molecule and is called dehydroretinol. Contained in the liver of freshwater fish.

The role in the body for the two forms of vitamin A is the same. For ease of understanding, they are combined under a common name - retinol or vitamin A.

Retinol is absorbed only in the presence of fats (photo: www.noanoliveoil.com)

Due to the fact that retinol is highly soluble in fat, it easily penetrates into adipose tissue and accumulates in the body. Therefore, when used in a dose of more than 200 mcg (micrograms) per day, it can cause symptoms of hypervitaminosis. Long-term continuous use of the drug has the same effect. Both deficiency and excess of vitamin A are harmful to health.

Therefore, the best option is to use natural retinol or carotene. Retinol from animal products is absorbed immediately and almost completely. Carotene from plants is first oxidized to retinol, then used by the body.

The poor absorption of vitamin A from plant foods, and the disruption of its absorption with an abundance of dietary fiber and a lack of fat, lead to the conclusion that it is necessary for vegetarians, and especially vegans, who do not use animal products for nutrition.

In the blood, vitamin A combines with transport proteins that deliver it to the liver. If a person does not get the vitamin from food, then its reserves in the liver can last for a year.

Retinol from the liver constantly enters the blood in small quantities and is transferred to the organs that consume it. A vitamin from food or a synthetic drug first goes to the liver to replenish reserves, and the remaining amount circulates in the blood.

In cells, retinol is converted into active forms - retinoic acid and retinal. Only in this form can they be used for integration into enzymes and biological compounds.

Active forms of retinol, when entering cells, trigger a chain of biological reactions described below.

1. Activates chondroitin, hyaluronic acid contained in cartilage, bone tissue and intercellular fluid.
2. Enhances the effect of heparin - thins the blood, reduces coagulation and the formation of blood clots.
3. Taurine, which is involved in the synthesis of growth hormone and in the transmission of nerve impulses, is activated by retinol.
4. Participates in the formation of liver enzymes that neutralize toxic substances.
5. Forms the pigment rhodopsin, which is responsible for night vision.
6. Somatomedins accelerate protein synthesis in muscle tissue, as well as collagen formation. They can only work in the presence of retinol.
7. Takes part in the production of female and male sexual hormones, immune factors: lysozyme, interferon and immunoglobulin A.
8. Prevents desquamation of the epithelium due to the formation of special enzymes in it.
9. Activates cell receptors for vitamin D.
10. Inhibits the growth of atypical tumor cells.

Taking vitamin A improves immunity (photo: www.legkopolezno.ru)

The biological functions of retinol are diverse and are associated with the growth and development of cells of all organs and systems. Vitamin A in the body is necessary for the following processes:

• Growth and formation of bones.
• Functioning of mucous membranes and skin epithelium (prevents dryness, desquamation and cell degeneration).
• It is part of rhodopsin in the retina and is found in cells that provide vision in low light.
• Maintains normal structure of hair, teeth and nails.
• Participates in the process of embryo formation, development of fetal organs and tissues.
• Stimulates the deposition of glycogen in the liver and muscle tissue.
• Participates in the synthesis of testosterone, estrogen and progesterone.

In addition, vitamin A prevents the development of malignant tumors, stimulates cellular immunity, enhancing phagocytosis and the formation of T-killer and T-helper cells, as well as antibodies for the humoral part of the immune response.

Vitamin A is an antagonist of the thyroid hormone - triroxine, so its use in thyrotoxicosis reduces heart rate, improves metabolic processes and the well-being of patients.

The antioxidant activity of vitamin A allows it to protect organs from damage by free radicals, which prevents aging and the development of atherosclerosis, diabetes and tumor processes. In addition to retinol, beta-carotene is also an antioxidant. It protects artery walls from cholesterol deposits and prevents angina pectoris.

The difference between medicine and poison is the dose. Vitamins are no exception. When consuming foods rich in vitamin A (shark, halibut or polar bear liver), poisoning of the body may develop with the following symptoms:

• Sudden drowsiness, weakness.
• Irritability.
• Dizziness.
• Increase in temperature.
• Cramps.

Nausea and vomiting, food intolerance and diarrhea may occur.

An overdose of vitamin A is dangerous for infants in this way: after 10 hours, symptoms of high cerebrospinal fluid pressure, vomiting, redness and rash on the skin appear.

If you take more than 10 thousand IU of retinol daily (1 IU of vitamin A: biological equivalent of 0.3 μg of retinol, or 0.6 μg of β-carotene), chronic vitamin A poisoning will develop. It is manifested by general malaise, fever, pain in the stomach, bones, muscles of the neck, back, legs, headache.

Vitamin A activity is measured in international units - IU. In this case, 1 mcg of retinol corresponds to 3.33 IU.

To establish the biological equivalence of retinol and beta carotene preparations, a standard has been adopted - 1 ER (retinol equivalent).

It corresponds to 1 mcg of retinol and 6 mcg of beta-carotene, 12 mcg of other carotenoids.

In terms of IU, the equivalent of retinol is 3.33 IU and 10 IU for beta-carotene.

Fish oil contains the most vitamin A (photo: www.mhealth.ru)

Plant sources described below.

Vegetables and fruits contain provitamin A, which gives them a yellow color - carrots, sweet peppers, tomatoes, pumpkin, peaches, apricots, sea buckthorn, cherries.

There is a lot of carotene in spinach, green onions, parsley and broccoli. It is also found in peas and soybeans, apples, grapes, melon and watermelon.

In addition, there are herbs with beta-carotene:

• Alfalfa.
• Burdock root.
• Borage leaves.
• Fennel.
• Horsetail
• Kelp.

To compensate for vitamin A deficiency, herbal remedies made from hops, lemongrass, nettle, oats, mint, sage and plantain, and raspberry leaves are used.

Animal sources are listed below.

The best sources of retinol are fish oil, caviar and beef liver, then egg yolk and butter, cream, sour cream, cheese and cottage cheese, and unskimmed milk. Meat and skim milk are low in vitamin A.

Vitamin A is essential for normal vision, it increases the synthesis of visual pigments and improves the recognition of visual objects. The carotenoids lutein and zeaxanthin protect the eye lens from clouding and prevent cataracts and blindness.

Retinol increases the barrier function of mucous membranes and enhances the immune response, protects against influenza and viral respiratory tract infections, and prolongs the life of seriously ill patients, including AIDS.

By protecting the mucous membranes of the digestive tract, it helps prevent exacerbation of gastritis and peptic ulcers, and accelerates the epithelization of ulcers.

A sufficient intake of vitamin A during gallstone disease reduces the risk of large stones, as it prevents the destruction and desquamation of the mucous membrane of the gallbladder.

With a normal supply of retinol, the urinary tract is protected from infection, which improves the course of cystitis and pyelonephritis.

The effect of vitamin A on the skin is manifested in the following actions:

• Acceleration of healing of wounds and burns, frostbite, postoperative sutures.
• Protection of the skin epithelium from keratinization and desquamation in dry skin and acne, psoriasis.
• Stimulating collagen synthesis in the treatment of aging skin, used for the prevention and treatment of wrinkles.

Retinol and its provitamin forms are used to treat infertility, as they participate in the formation of progesterone and spermatogenesis, necessary for the formation of embryonic tissues of the fetus, and prevent malformations of the child.

Protecting organs from oxidative damage gives vitamin A the ability to prevent aging of the body, inflammation of the inner wall of blood vessels, atherosclerosis and cancer.

To meet the daily requirement for vitamin A, it must be consumed in the dose indicated in the table. To convert to IU, you need to multiply the dose in mcg by 3.33. For medicinal purposes, higher doses are recommended (as prescribed by a doctor).

source

First isolated from carrots (corota). Carotene is found in carrots - this is a provitamin; vitamin A is formed from it in the intestines and liver. It affects human growth, improves skin condition, promotes the body's resistance to infections, ensures the growth and development of epithelial cells, and is part of the visual pigment of the retina. rhodopsin, which regulates dark adaptation of the eye. Vitamin A is involved in energy metabolism, regulation of glucose formation, biosynthesis of corticosteroids, and affects membrane permeability.

Vitamin A deficiency leads to damage to epithelial tissue with characteristic skin lesions, characterized by dryness, a tendency to rhinitis, laryngotracheitis (inflammation of the mucous membrane of the larynx and trachea), bronchitis, pneumonia, impaired twilight vision, conjunctivitis (inflammation of the eye) and xerophthalmia (dryness of the mucous membrane and cornea of ​​the eye) which in severe cases of the disease are replaced by perforation of the cornea and blindness.

Hypovitaminosis A affects the epithelium of the gastrointestinal tract and urinary tract. Violation of the barrier properties of the epithelium, combined with changes in the immune status due to vitamin A deficiency, sharply reduces the body's resistance to infections. The skin becomes dry and rough on the arms and calves, peels off, and keratinization of the hair follicles makes it rough. Nails become dry and dull. Weight loss, even to the point of exhaustion, is also noted; in children, growth retardation occurs.

With hypervitaminosis of vitamin A, drowsiness, lethargy, headache, nausea, vomiting, irritability, gait disorder, pain in the bones and lower extremities, yellow discoloration of the skin, hair loss, loss of calcium salts from bone tissue are observed.

Vitamin A is found only in products of animal origin (fish oil, milk fat, butter, cream, cottage cheese, cheese, egg yolk, liver fat and fat from other organs - heart, brain). However, in the human body (in the intestinal wall and liver), vitamin A can be formed from certain pigments called carotenes, which are widely distributed in plant foods. B-carotene (provitamin A) has the greatest activity. It is believed that 1 mg of b-carotene is equivalent in effectiveness to 0.17 mg of vitamin A (retinol).

A lot of carotene is found in rowan berries, apricots, rose hips, black currants, sea buckthorn, pumpkin, watermelons, red peppers, spinach, cabbage, celery and parsley tops, dill, lettuce, carrots, sorrel, green onions, green peppers, nettles, dandelion, clover.

The daily requirement of an adult for vitamin A is 1-2.5 mg, for pregnant and lactating women - 1.25-1.5 mg, for children in the first year of life - 0-0.4 mg. The need increases during development and growth, as well as in diabetes and liver disease.

Vitamin A can withstand high temperatures for a short time. The vitamin is sensitive to oxidation by atmospheric oxygen and to ultraviolet rays. It is better to store products containing vitamin A in a dark place. Vitamin A is better absorbed and absorbed in the presence of fat.

Vitamin D (calciferol, xerophthalmic)– ensures the absorption of calcium and phosphorus in the small intestine. Vitamin D helps in the fight against rickets.

Vitamin D deficiency leads to disturbances in phosphorus-calcium metabolism, which can result in rickets, which leads to insufficient lime deposition in the bones. With hypervitaminosis of vitamin D, severe toxic poisoning is observed: loss of appetite, nausea, vomiting, general weakness, irritability, sleep disturbance, fever. Deposition of calcium salts in internal organs (kidneys), premature mineralization of the skeleton, growth retardation in children.

There is practically no vitamin D in plant foods. Most of the vitamin is found in some fish products: fish oil, cod liver, halibut, and Atlantic herring. In eggs its content is 2.2%, in milk - 0.05%, in butter - 1.3%, very much in the liver of a dolphin, seal, polar bear; It is present in small quantities in mushrooms, nettles, yarrow, and spinach.

The formation of vitamin D is promoted by ultraviolet rays. Vegetables grown in greenhouses contain less vitamin D than vegetables grown in the garden, since the glass frames of the greenhouse do not allow these rays to pass through.

The need for vitamin D in adults is met through its formation in human skin under the influence of ultraviolet rays and partly through its intake from food. In addition, the adult liver is capable of accumulating a noticeable amount of vitamin D, sufficient to meet its needs for 6 months. The daily requirement of the vitamin for an adult is 0.025 - 1 mg.

Vitamin E (tocopherol, antioxidant effect) According to its chemical structure, it belongs to the group of alcohols. Tocopherol is a reproduction vitamin that has a beneficial effect on the functioning of the reproductive and some other glands. Its effect on metabolism in muscle tissue is especially significant. Participates in the synthesis of creatine phosphate - one of the most important macroergs of the heart muscle and skeletal muscles, helps maintain high levels of muscle hemoglobin, participates in the regulation of muscle mineral metabolism, and in the regulation of the synthesis of steroid hormones.

Vitamin E deficiency can develop after significant physical overload. In animals deprived of vitamin E, degenerative changes were found in skeletal muscles and cardiac muscles, muscular dystrophy, a decrease in muscle tissue mass (due to the protein myosin), increased permeability and fragility of capillaries, decreased mobility, and paralysis.

Tocopherols are found mainly in plant foods. The richest in them are unrefined vegetable oils: soybean, cottonseed, sunflower, peanut, corn, sea buckthorn. Sunflower oil contains the most vitamin-active α-tocopherol. Vitamin E is found in almost all foods, but it is especially abundant in grains, legumes, and vegetables: cabbage, tomatoes, lettuce, peas, spinach, parsley tops, and rosehip seeds. Small amounts are found in meat, fat, eggs, milk and beef liver.

The daily requirement for tocopherol for adults is 12-15 mg (according to other literature 5-30 mg), for children of the first year of life - 5 mg. Vitamin E is very stable, it is not destroyed by the action of alkalis and acids, or by boiling or heating to 200 0 C. Thus, it is preserved during cooking, drying, canning and sterilization. The vitamin can accumulate in the body, as a result of which vitamin deficiency does not occur immediately.

Vitamin K (naphthoquinone, phylloquinone, antihemorrhagic) necessary for the synthesis of blood clotting factors in the liver (for example, hemoglobin ) . A healthy body produces vitamin K itself, produced by intestinal microflora and supplied with food.

The most important biological role of vitamin K is due to its participation in blood clotting. Vitamin K deficiency manifests itself in a slowdown in blood clotting and the development of subcutaneous, intramuscular and other hemorrhages (hemorrhages), as well as in a slowdown in the conversion of fibrinogen to fibrin. Along with this, changes in the functional activity of skeletal and smooth muscles are noted, and the activity of a number of enzymes decreases.

Vitamin K is widely distributed in the plant world. The green leaves of alfalfa, spinach, chestnut, nettle, and yarrow are especially rich in it. There is a lot of vitamin in rose hips, white, cauliflower and red cabbage, carrots, tomatoes, strawberries.

The daily requirement for vitamin K in adults is approximately 0.7-1.4 mg (according to other literature, 10-15 mg). Vitamin K is delivered to the body mainly through food and is partially formed by intestinal microflora. Absorption of the vitamin occurs with the participation of bile. The cause of vitamin deficiency: impaired absorption of fats (blockage of the bile ducts and failure of bile to enter the intestines), inhibition of intestinal microflora by antibiotics. Vitamin K is destroyed by heat treatment.

B vitamins. These vitamins are included in enzymes as coenzymes. Among them are:

Vitamin B 1 (thiamine) plays a primary role in the metabolism of carbohydrates: the higher the level of their consumption, the more thiamine is required. In its absence, polyneuritis develops. It is part of the enzyme pyruvate decarboxylase, which decarboxylates PVK, a poison for the body. Thiamine plays an important role in protein metabolism: it catalyzes the removal of carboxyl groups and participates in the processes of deamination and transamination of amino acids. Involved in fat metabolism, participating in the synthesis of fatty acids, which prevent the formation of stones in the liver and gall bladder. Affects the function of the digestive organs, increases the motor and secretory functions of the stomach, accelerating the evacuation of its contents. It has a normalizing effect on the functioning of the heart. This vitamin is a sulfur-containing vitamin. In its pure form, these are colorless crystals with the smell of yeast, highly soluble in water. Thiamine enters the body with food, and is partially formed by intestinal microorganisms, but in an amount that does not satisfy the physiological needs for it. The daily requirement is from 1.3 to 2.6 mg (0.6 mg per 1000 kcal). (2-3 mg when playing sports 5-10 mg).

With a lack of food, PVC accumulates in the blood and nervous tissue, which first leads to a disorder of the central nervous system and peripheral nervous system, manifested in muscle weakness, insomnia, and cardiac dysfunction.

Thiamine is found in greater quantities in yeast, in the shell of grain crops, in buckwheat, in oatmeal, in potatoes. It is thermostable in an acidic environment at pH 0 C; in an alkaline environment it is destroyed when heated. Frying and storing dry foods have virtually no effect on the thiamine content.

Vitamin B 2 (riboflavin) participates in growth processes, in the metabolism of proteins, fats and carbohydrates, it has a regulatory effect on the state of the central nervous system, affects metabolic processes in the cornea, lens, retina, and provides light and color vision.

It is part of biological oxidation enzymes, ensuring the transfer of H in the respiratory chain. Hypovitaminosis - a violation of biological oxidation processes, inflammation of the mucous membranes of the oral cavity, tongue, painful skin cracks in the corners of the mouth, eye disease (mild visual fatigue, photophobia). It mainly enters the body with food, but in humans it can be synthesized by intestinal microflora. The daily requirement is 0.8 mg per 1000 kcal. (2-4 mg/day)

Resistant to heat, but very sensitive to ultraviolet rays. There is a lot of vitamin in meat, liver, green vegetables, kidneys, milk and yeast.

Vitamin B 3 (pantothenic acid)

Vitamin B in tissues 3 undergoes phosphorylation (cleavage of a phosphoric acid residue) and is part of coenzyme A (CoA), which plays a critical role in the metabolism of carbohydrates, fats, and proteins. Vitamin deficiency is unknown, since the need is completely satisfied (10 mg/day) by the intestinal microflora. In animals, vitamin deficiency manifests itself: graying of the coat, dysfunction of the adrenal glands.

Sources: yeast, fish roe, liver, green parts of plants.

Vitamin PP(nicotinic acid and its amide - nicotinamide, vitamin B 5) is part of the enzymes - oxidative dehydrogenases NAD and NADP, involved in cellular respiration and protein metabolism, regulating higher nervous activity and the functions of the digestive organs. Used for the prevention and treatment of pellagra, diseases of the gastrointestinal tract, sluggishly healing wounds and ulcers, atherosclerosis.

Vitamin deficiency: decrease in NAD and NADP, disruption of the normal course of oxidative processes as a consequence of pellagra: skin lesions (dermatitis), on exposed parts of the body exposed to sunlight, diarrhea, mental disturbances (memory loss, hallucinations, delirium). In case of overdose or hypersensitivity, redness of the face and upper half of the body, dizziness, a feeling of a rush to the head, and urticaria may occur.

The main sources of vitamin PP are meat, liver, kidneys, eggs, and milk. Vitamin PP is also contained in bread products made from wholemeal flour, cereals (especially buckwheat), legumes, and is present in mushrooms.

The daily requirement for vitamin PP for an adult is 14-18 mg (15-25 mg/day). Vitamin PP can be synthesized in the human body from the essential amino acid tryptophan, which is part of proteins.

Vitamin PP is relatively resistant to heat treatment.

Vitamin B 6 (pyridoxine) coenzyme of enzymes that ensure the conversion of amino acids, ensures the normal absorption of proteins and fats, plays an important role in nitrogen metabolism, in hematopoiesis, and affects the acid-forming functions of the gastric glands. In its pure form it is colorless crystals, highly soluble in water. The daily requirement for pyridoxine is 1.5-3 mg (2-3 mg), increases with rapid growth, under the influence of physical activity.

Vitamin B 6 is resistant to acids, alkalis, high temperatures, and sunlight destroys it. Cooking pyridoxine is even beneficial, since it releases its active parts. Long-term storage leads to the destruction of pyridoxine, and in warm conditions this process occurs much more intensely.

Vitamin deficiency: skin inflammation, loss of appetite, weakness, decreased number of lymphocytes in the blood.

Sources: wheat germ, yeast, liver, some amount is synthesized by intestinal microflora. The vitamin is found in meat, fish and milk.

Vitamin B 12 (cyanocobalamin) belongs to substances with high biological activity. The vitamin has a very complex structure: four pyrrole rings, in the center there is a Cu ion, a nucleotide group.

The main importance of this vitamin is its antianemic effect, in addition, it has a significant effect on metabolic processes - proteins, the synthesis of amino acids, thymine nucleotides and deoxyribose, necessary for the construction of RNA, and participates in hematopoiesis processes. In children, it stimulates growth and causes an improvement in general condition. Daily requirement 0.3g. (1 mcg).

Helminthic infestations can completely deprive the body of vitamin B 12. When consuming white bread, which has little fiber necessary for the normal existence of microflora, and also contains baker's yeast, the synthesis of vitamin B 12 will be impaired. The result can be anemia and anemia. Sources: liver, milk, eggs, intestinal microflora.

Vitamin B 15 (pangamic acid) or calcium salt. It activates oxygen metabolism and is used for acute alcohol and drug poisoning. Exhibits a lipotropic effect (prevents the accumulation of cellular elements in the liver with blood and lymph.)

Pangamic acid improves the general condition: vigor and appetite appear, sleep is normalized, and local symptoms are mitigated. The use of pangamic acid also stabilizes the activity of the pituitary-adrenal system and the central nervous system.

Vitamin B 15 is involved in oxidative processes, improves the trophism of the heart muscle as a result of stimulation of the biosynthesis of creatine and creatine phosphate, as well as as a result of activation of respiratory chain enzymes. It has a positive effect during oxygen starvation.

The antitoxic effect of pangamic acid is explained by its participation in the biosynthesis of choline, which binds and removes toxic substances. Positive results were obtained when treating patients with vitamin B 15. There is a disappearance of cravings for drugs and alcohol.

Vitamin C (ascorbic acid) participates in redox processes, protects active thiol groups (- H) of enzymes from oxidation, important role in the metabolism of proteins and carbohydrates, protein synthesis of connective tissue (collagen), bone (ossein), teeth (dentan). Participates in the formation of adrenal steroid hormones. With hypervitaminosis of vitamin C, dysfunction of the liver and pancreas is possible.

Contained in fresh plants: rosehip, dogwood, black currant, rowan, sea buckthorn, citrus fruits, red pepper, horseradish, parsley, green onions, dill, watercress, red cabbage, potatoes, rutabaga, cabbage, and vegetable tops. In medicinal plants: nettle, forest fruits.

The optimal requirement for vitamin C for an adult is 55 - 108 mg (50-75 mg), pregnant and lactating women - 70-80 mg, under the influence of intense muscle activity 100-150 mg,

Vitamin C is very unstable. It decomposes at high temperatures, in contact with metals, and when vegetables are soaked for a long time, it turns into water and quickly oxidizes.

Vitamin P (rutin) unites a group of about 500 biologically active substances - bioflavonoids. All of them are products of plant origin; these substances are not found in animal tissues. The vitamin normalizes the condition of capillaries and increases their strength, reduces the permeability of vascular walls. Helps maintain good condition of collagen-cement between all cells.

The main sources of vitamin P are citrus fruits (especially the peel), vegetables, nuts, and seeds.

As a result of vitamin P deficiency, capillary fragility occurs due to a lack of collagen, which leads to the rapid formation of bruises.

The main functions of vitamin P are to prevent bruising and strengthen capillary walls. It is involved in creating protection against infections and colds, prevents bleeding from the gums and strengthens the teeth in the gums.

Vitamin P and vitamin C are best taken together. The need for the vitamin has not been established; it is approximately half the amount in relation to vitamin C. The lack of vitamin P is not compensated for by vitamin C. They talk about the interdependence of the effects of these vitamins.

Vitamin H (biotin, antiseborrheic) heterocyclic compound, imidazole and thiophene rings can be distinguished in the structure, the side chain is represented by a valeric acid residue. It is part of enzymes as a coenzyme and accelerates carboxylation reactions.

Hypovitaminosis: inflammation of the skin, hair loss, increased secretion of fat by the sebaceous glands (seborrhea), therefore antiseborrheic.

The need is met through its synthesis by intestinal bacteria. Some part comes from food: peas, soybeans, cauliflower, mushrooms, yolk, liver.

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