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Fat-soluble, so it can accumulate in the liver, and therefore is moderately toxic. It is an antioxerophthalmic (necessary for normal vision) remedy. Its composition is С20Н29ОН (more precisely - С20Н30О). In principle, vitamins can be considered as alcohols, but only by the mechanism of their action. Heat treatment as a whole can withstand, although up to 35% of retinol is lost during cooking, with hot water and canning. For many years, the main industrial source of vitamin A was fish oil (cod liver oil), but with the deterioration of the ecology of the world's oceans, the demand for cod liver fell. In addition, it was found that its content in the shark liver is a thousandfold higher than in the cod liver. At one time, the program of compulsory intake of fish oil by young children was intensively imposed, without taking into account the possibilities of assimilation of fat-soluble vitamins by a child's organism. Today, the "transformer" preparations that make the transfer of fat-soluble vitamins into a water-soluble form are quite accessible, their use excludes the "replanting" of the baby's liver. But how many pediatricians are aware of the existence of such drugs, not to mention the name? That's just it.
Retinol provides:
• normal vision;
• normal condition of bones, teeth, gums, respiratory tract;
• Integrity of epithelial cells that form the skin, mucous membranes of the mouth, intestines, genital tract;
• normal functioning of the cardiovascular system (in conjunction with other important
vitamins);
• production of sperm and the development of eggs.
Deficiency of retinol causes a decrease in growth parameters. The most assimilable precursor of retinol is beta-carotene (C40H56), which turns into vitamin A already in the body. A lot of beta-carotene in carrots.
When there is a shortage of tocopherol (vitamin E), vitamin A oxidizes too quickly, which must be taken into account. It is important to know the interaction of retinol with zinc: when
deficiency of zinc disturbs the process of transformation of vitamin A into an active form that can penetrate into the blood, and through the blood - to the tissues. In turn, retinol promotes the assimilation of zinc.
The intake of mineral oils, for example, as a laxative, leads to hypovitaminosis of all fat-soluble vitamins: the body does not absorb mineral oils, and fat-soluble vitamins, dissolved in mineral oils, are excreted through the intestines, being turned off from metabolic processes.
Vitamin A is absorbed only if there is an appropriate volume of protein. Reactions to vitamin A overdose are strictly individual, so the increase in dosages should be monitored in the dynamics of the change in state. There are cases when an overdose of vitamin A in the diet of pregnant women led to the birth of children with congenital malformations. This is due to a violation of the liver - the largest gland and the most important "laboratory" of the body. An overdose of beta-carotene is almost impossible, especially since it is completely non-toxic.
With a deficiency of vitamin A, the following symptoms appear:
• dry skin, mucous membranes of the mouth, eyes (up to the ulceration of the cornea);
• rash of acne;
• thickening and scaly skin on the soles and palms;
• fast fatiguability;
• weight loss;
• reduced visual acuity at dusk - "night blindness".
With overabundance (hypervitaminosis):
• weakness, malaise, night sweats;
• pain in the joints and bones;
• pain in the abdomen, headache with nausea and vomiting;
• hair loss and brittle nails;
• violations of the menstrual cycle until complete cessation.
Let the similarity of symptoms in hyper- and hypovitaminosis do not surprise you, it is a graphic illustration of the consequences of a balance imbalance.