Vitamin A: what foods contain and what it needs for a person
Jul 08, 2018
Vitamin A is considered to be a group of fat-soluble compounds( lipovitamins).It is able to be deposited in the body, mainly in the liver.
According to the WHO, with vitamin A deficiency, none of the food products can cover its deficiency, so retinol is required in the form of pharmacological preparations.Table of Contents: Synthesis of Vitamin A What is Vitamin A Why do I need Vitamin A?Vitamin A for pregnant women How much vitamin A is required per day?Hypovitaminosis: Causes and Symptoms Indications for Vitamin A Hypervitaminosis
Synthesis of Vitamin A
Vitamin A is produced in the body from pro-vitamins "carotenoids" that come in from the outside.The term comes from carrot( carrots, English), because these precursor substances were first discovered in carrots.Related compounds are present in a number of vegetables and fruits( especially yellow, red and orange), as well as in algae and certain species of fungi.
Currently, more than half a thousand carotenoids are known to science.
The most common of these are:
- a-, b- and d-carotene;
Beta-carotene undergoes oxidation in the human liver and, in splitting, forms vitamin A.
The unit of measurement for retinol is 1 ER, which corresponds to 1 μg of retinol, 6 μg of b-carotene or 12 μg of other carotenoids.
1 μg is 3.33 IU for retinol or 10 IU for b-carotene.
What is Vitamin A?
Important: has experimentally proven that beef, skimmed milk, and cereals contain insufficient amounts of carotene and retinol, that is, they can not serve as full-fledged sources of vitamin A.
Animal products containing vitamin A:
- beef liver;
- cod liver;
- fish oil;
- caviar of sea fish;
- whole milk;
- egg yolk.
- pepper( "Bulgarian" and burning cayenne);
- broccoli cabbage;
- seaweed( seaweed kelp).
Important: is a lot of provitamin A present in herbs such as alfalfa, horsetail, peppermint, lemongrass, nettle, sage, hops, plantain and sorrel.
Why do I need vitamin A?
Vitamin A takes part in a number of metabolic processes taking place 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 it, the fat reserves necessary to man are formed.
Note: 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);He takes part in the biosynthesis of the pigment of the retina.The most important carotenoids prevent cataracts and significantly reduce the likelihood of the development of macular degeneration - pathology, which is one of the main causes of blindness.
Vitamin A is one of the most effective natural antioxidants.It minimizes the harmful effects of free radicals, which allows the use of retinol and carotenoids for the prevention and treatment( as part of complex therapy) of cancer.In clinical trials, it has been shown that b-carotene reduces the likelihood of recurrence of malignant neoplasms after surgical intervention.
Antioxidant effect prevents 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 the body needs.
The carotenoid lycopene, which is found in large amounts in tomatoes, prevents the deposition of cholesterol on the vascular walls, thus protecting a person from atherosclerosis and its dangerous consequences.This provitamin also reduces the likelihood of developing malignant lesions of the uterus and breast, as well as prostate cancer.
The state of nonspecific immunity largely depends on vitamin A.The compound is able to increase the resistance of the organism to infectious agents of bacterial and viral nature( phagocytic activity of leukocytes significantly increases).
Adequate intake of vitamin A with food reduces the likelihood of developing influenza, colds, as well as infections of the genitourinary and respiratory systems and organs of the gastrointestinal tract.
Children who eat well and regularly get retinol and carotenoids in the right amount, are much easier to tolerate "chickenpox" and measles.
The constant presence of a sufficiently high level of retinol in the serum significantly increases the life expectancy of patients suffering from AIDS.
Vitamin A is actively involved in the regeneration of the epithelial layer of the skin and mucous membranes.Its drugs are widely used in the therapy of any dermatosis( acne, psoriasis, etc.), as well as skin damage due to mechanical injuries or burns.Thanks to the stimulation of the process of collagen biosynthesis, retinol provides an early healing, reducing the risk of developing secondary infectious complications many times over.Vitamin A significantly improves the quality of tissue newly formed in place of significant damage.
Note: in many modern cosmetic products includes retinoid substances, which are nothing more than synthetically obtained analogues of vitamin A. Creams with retinoids very well help with sunburn.
The beneficial effect of retinol on epithelial cells provides an improvement in the functional activity of the bronchi and lungs.Acquiring patients with vitamin A preparations allows to accelerate recovery in such pathologies of the digestive tract as peptic ulcer and colitis( inflammation of the mucous membranes of the walls of the large intestine).
Vitamin A for pregnant women
Retinol is one of the most important organic compounds necessary for the normal intrauterine development of a future child.
Women who are preparing to become mothers are advised to consume enough vitamin A to improve fetal nutrition and reduce the likelihood of a child with underweight.
For pregnant women, the daily intake of retinol should be 750-770 μg.For nursing mothers, the norm recommended by Russian doctors is more - 1200-1300 mcg.
Important: should not consume more than 6000 IU per day during childbearing, 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 μg) during the day.Against the background of pathologies due to hypovitaminosis A, consumption is recommended to be increased 3 times( up to 10,000 IU).
Important: climatic conditions can affect the body's need for vitamin A. Cold weather does not have any effect on the exchange of retinol, but the hot climate makes its own adjustments: the demand for this vitamin is growing significantly.
Babies of the first year of life require 400 micrograms of retinol per day.Children from 1 year to 3 years need 450 μg of vitamin, at the age of 4 to 6 years - 500 μg, and from 7 to 10 years - 700 μg per day.
For teenagers the norms are the same as for adults.
Men are recommended to consume at least 1000 micrograms per day, and for women, 800 μg is considered optimal figures, regardless of age.
Note: need is reduced in women who take birth control pills.
Hypovitaminosis: Causes and Symptoms
Vitamin A levels in plasma are considered to be inadequate if it is below 0.35 μmol / L.
Even at a level of 0.70-1.22 μmol / l, the amount of retinol in its main "store", i.e., in the liver is markedly reduced.
The main reasons for the development of hypovitaminosis include:
- a low level of vitamin A in foods;
- unbalanced power;
- liver pathology;
- colitis, enteritis;
- is a malabsorption syndrome;
- condition after resection of the small intestine.
For the full absorption of vitamin A, you need to consume enough fat and a high-grade protein.In the food must necessarily be present vitamin E, the absence of which hampers the absorption of retinol.
Important: hypovitaminosis A is often noted in vegetarians who do not substitute animal products with the necessary volume of high-grade vegetable protein.
The characteristic manifestations of hypovitaminosis include:
- increase in temperature sensitivity;
- reduction of pain threshold;
- early aging of the skin( 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 crust formation in the corners of the eyes;
- urinary incontinence( weakness of the sphincter);
- hyperesthesia( pathologically high sensitivity) of tooth enamel;
- impaired erectile function;
- early ejaculation.
A very characteristic manifestation of retinol deficiency is hemorrhagia, a significant deterioration in vision at dusk.
Consequences of lack of vitamin A:
- xerophthalmia( dry eye cornea);
- corneal opacity;
- precancerous pathology and skin cancer;
- atrophic gastritis;
- Inflammation of the intestine;
- decreased sexual desire;
- malignant breast tumors;
- gynecological diseases( cervical erosion, etc.);
- cachexia( malnutrition);
- anemia( anemia);
- frequent respiratory infections;
- cystic liver formation;
Indications for the intake of vitamin A
Vitamin A is administered orally, for injection administration( IM) or for topical use if diagnosed:
- skin and mucosal pathology;
- inflammation of the cornea and conjunctiva of the eyes;
- burns, fractures and other injuries( to accelerate regeneration).
Recommended dosages for the treatment of
Light and medium hypovitaminosis require dosing up to 33,000 IU for adult patients and 1,000 to 5,000 for children.For skin diseases, the dosages above are 50000-100000 and 5000-10000 IU, respectively.
Important: Vitamin A exerts a toxic effect on the body when consuming 25,000 IU per day.
Symptoms of hypervitaminosis:
- pain in the abdominal region;
- of arthralgia;
- "zaedy" in the corners of the mouth;
- delayed monthly;
- dry skin;
- increased brittleness and thickening of the nail plates.
Important: Zinc deficiency leads to impaired retinol digestion.
The combination of vitamin A and ethanol causes more damage to the liver than the effects of alcohol.
More detailed information on the vitamins of groups A you will get by watching this video review:
Konev Alexander, therapist