Vitamins of group A are subdivided into substances similar in chemical and molecular structure – retinoids and carotenoids, and are characterized by a different nature of origin: animal and vegetable. The most important for the human body are retinol and beta-carotene. Retinol is more typical of food sources of animal origin, such as meat, cheese, butter, and dairy products, and some seasonal vegetables and fruits, as well as root vegetables, are especially enriched in beta-carotene.
Vitamin A refers to the “beauty vitamin.” In combination with vitamin E, the substance helps to improve the elasticity of hair and skin, strengthen nails, and also significantly prolongs the youth of the human body. It has pronounced regenerating functions, has an antioxidant effect, enhances general immunity and prevents the penetration of viral infections into the body. Therefore, the substance is called anti-infective vitamin. Vitamins of group A are extremely important for childbearing functions. They normalize the work of the sex glands, contribute to the enhanced production of seminal fluid and significantly improve its quality; in women – are actively involved in the development of the egg. Vitamins of group A well influence sight, interfere with development of ophthalmologic diseases and deviations, including hemeralopia. The substance is necessary for people who spend a long time in front of a screen or computer monitor, or work in low electric light.
Table of the daily requirement of vitamin A (retinol) for the human body (mg / day):
The liver is a depot for vitamin A, it is not excreted from the body for quite a long time and can accumulate in significant quantities. Therefore, the abuse of retinol and beta-carotene is somewhat dangerous and can lead to hypervitaminosis.
Retinol in food
It is the best of all to receive any vitamins from food sources, than using multivitamin complexes and other pharmaceutical preparations. This is due to the presence of other beneficial micronutrients that contain products, as they facilitate absorption and have a number of other beneficial properties. Which products contain retinol and beta-carotene, and what is the concentration of the substance in each of them, the following table will show.
Beta-carotene in food
When injected into the human body, theoretically, each beta-carotene molecule produces two molecules of pure vitamin A. In practice, it turns out a little differently – some beta-carotene actually transforms into pure vitamin, the remaining one invariably resides in the human body as a carotenoid. Thus, it provides an untouchable temporary supply of vitamin A in the body, and if there is a shortage of it, beta-carotene begins to actively produce it independently.
Beta-carotene is a prophylactic agent of cancer, it actively interacts with other vitamins, and in these combinations, performs many useful functions: strengthens the immune system, reduces blood cholesterol levels, protects against toxic substances and poisons, improves the central nervous system, increases stress tolerance and performance.
Products containing beta-carotene, mainly of plant origin. Some seasonal fruits, vegetables and root crops are especially rich in substance. The daily rate of the element, in contrast to vitamin A, ranges from 2 to 5 mg for an adult. The following table lists the approximate amount of beta-carotene in mg that the listed products contain.
Vitamin tolerates heat treatment, the products retain a concentration of the substance even when frying. Moreover, beta-carotene is best absorbed in combination with animal and vegetable fats.
Lack of retinol and beta-carotene in humans
Products containing vitamin A should be eaten in sufficient quantities throughout the year. If vegetables and fruits fortified with beta-carotene have a seasonal harvest, they should be replaced with other food sources of nutrients, if necessary, increasing their consumption to achieve the daily intake of vitamin ingested.
Vitamin A hypovitaminosis is due to the following factors:
- Vitamin A deficiency in foods;
- Lack of fat intake. Retinol and beta-carotene are fat soluble substances;
- Eating and eating disorders, lack of the necessary amount of protein in the diet;
- Insufficient intake of products containing vitamin E (it prevents the oxidation of vitamin A, acting as an antioxidant);
- Chronic diseases of the gastrointestinal tract;
- Diseases of the liver and gallbladder;
Symptoms of hypovitaminosis:
- The main symptom of vitamin A deficiency is a sharp deterioration in vision at dusk or in dim lighting;
- Premature signs of aging of the skin, the formation of wrinkles;
- Dry eyes, redness, ophthalmic inflammatory diseases (conjunctivitis);
- Severe tearing of the eye due to temperature changes in the air and windy weather;
- Enhance the sensitivity of tooth enamel;
- Dandruff, seborrhea, dry skin and peeling;
- Increased pain sensitivity;
- In men, an erection weakens or disappears, premature ejaculation, weakening of the bladder sphincter function appear.
Diseases that can cause vitamin A deficiency:
- Ophthalmologic diseases of any complexity and etiology;
- Acne, skin aging, seborrhea, dermatitis, precancerous syndromes and cancer;
- Erosion and polyps of the cervix in women;
- Chronic atrophic gastritis;
- Breast and breast cancer;
- Chronic respiratory diseases and viral infections;
- Disorders of brain activity, growth retardation;
- Sleep disturbance
Vitamin A interaction with other substances. Recommendations regarding the handling and storage of products
Products containing vitamin A and beta-carotene, tolerate heat treatment. However, you should not overdo it – fresh vegetables and fruits are always better than boiled ones, and meat, steamed or grilled, saves more vitamins and trace elements than fried in oil. When consuming vitamin A, one should not forget about its combination with vitamin E. The second one has antioxidant properties, preventing retinol from oxidizing and improving its absorption. Attention should be paid to what products in the daily menu contain zinc, and whether its quantity in the daily diet is sufficient. It is zinc that converts vitamin A into active forms, so interaction with it is also necessary.
With enhanced nutrition based on vitamin A, you should be wary of taking alcohol. The interaction of retinol and ethanol can lead to dysfunction of the liver, and its serious diseases. Taking laxatives disrupts the absorption of fat-soluble vitamins, including vitamin A. Laxative herbal preparations do not carry such dysfunctions. Acceptance of hyperlipidemic drugs (drugs that lower cholesterol levels), you need to take into account their functions that violate the absorption of fat-soluble vitamins. This combination will not incur harm, but it can neutralize the beneficial functions of vitamin A, due to its poor absorption.
Ultraviolet radiation and oxygen, in contrast to heat treatment, can carry destructive processes for vitamin A. Therefore, products enriched with the substance should not be stored under open sunshine and in the wind. So they can lose some useful properties.
In winter and autumn, lower levels of retinol should be taken into account in dairy products. This is due to artificial feeding of cows and the lack of fresh grass in their diet. Accordingly, the amount of vitamin A is reduced by up to 4 times in products that are made from milk.