As with vitamin D, vitamin E and vitamin K, vitamin A is a fat-soluble vitamin. In colloquial language, retinol is often equated with vitamin A, but strictly speaking, vitamin A is not a single vitamin but a group of substances. In addition to retinol (vitamin A1), these include, for example, retinal, retinoic acid and retinyl palmitate. Vitamin A can either be taken directly by eating animal foods or by the body provitamin A (beta-carotene), which is contained in plant foods produced.
Effect of Vitamin A.
Vitamin A is needed in our body for the maintenance of a wide variety of processes. It is particularly important for the visual process. In particular, vitamin A has an effect on the night vision - a deficiency can lead to night blindness. This is due to the fact that vitamin A is the precursor for various visual dyes and is therefore of crucial importance for color differentiation and light and dark differentiation.
In addition, vitamin A also influences the structure of the skin and mucous membranes by promoting cell growth. In addition, it prevents damage to the DNA in the skin cells or supports the repair of existing damage. In addition, vitamin A is also crucial in the formation of new erythrocytes.
Since vitamin A promotes the growth of the skin and mucous membranes, it also has a positive effect on our immune system - because the skin and mucous membranes are healthy, bacteria or viruses can penetrate more difficult in our body. In addition, vitamin A also increases the number of leukocytes and thus strengthens our immune system. Therefore, even with a slight vitamin A deficiency increases the risk of getting sick by two to three times.
Vitamin A is important for our bones
Vitamin A is also involved in various metabolic processes in our body. It mainly affects protein metabolism but also lipid metabolism. Due to its involvement in protein metabolism, a protein-rich diet can result in vitamin A deficiency.
An adequate supply of vitamin A is especially important for children. Because vitamin A has an influence on the structure and growth of our bones and plays a decisive role, especially for the healing process of bone fractures. But vitamin A is also important for adults, as it plays an important role in the synthesis of estrogen and testosterone. In addition, it affects the oogenesis and spermatogenesis and also the number and shape of the sperm depend on the supply of vitamin A.
Vitamin A acid
Vitamin A acid - also called tretinoin or all-trans retinoic acid - is a breakdown product of vitamin A. The acid is used, for example, in creams or alcoholic solutions used to treat acne or other skin diseases. The vitamin A acid eliminates cornification disorders, inhibits sebum production, and replenishes the skin.
However, acne treatment with vitamin A acid usually has significant side effects, it can lead to redness, burning, itching and a blossoming of acne. Because of this, the treatment with vitamin A acid in comparison to other treatment options nowadays only plays a subordinate role.
In addition, vitamin A acid is also used in various cosmetics to prevent premature aging of the skin. The premature aging of the skin is mainly due to UV light, as it inhibits the formation of collagen and promotes the breakdown of collagen fibers. Vitamin A acid can protect the skin from these two harmful processes and is therefore used in some anti-aging creams. However, since skin irritation can occur when using the acid, in Germany creams use only the more harmless retinol.
Vitamin A in food
In animal foods, vitamin A is present in one of its manifestations - mostly as retinyl palmitate -, whereas in plant foods it occurs in the form of provitamin A (ß-carotene). High levels of vitamin A are found in the following foods:
- egg yolk
- Liver products (especially beef)
By contrast, provitamin A is found mainly in carrot juice and in raw and cooked carrots. Other herbal foods that are high in provitamin A are apricots, cantaloupe melons, kale, spinach and pumpkin. Compared to vitamin A, provitamin A has the advantage of being converted into vitamin A in the body only when needed.
Daily need for vitamin A
The daily requirement for vitamin A can be met both by the supply of vitamin A and provitamin A (beta-carotene). It depends on age, circumstances and gender - in men, the daily need is slightly higher than in women.
The daily dose of vitamin A is about 1 milligram for an adult. If only provitamin A is added, the daily dose should be 2 milligrams. If the body is supplied with both vitamin A and provitamin A, a daily dose of 0.5 milligrams of vitamin A and 1 milligram of provitamin A is recommended.
Since the vitamin is poorly tolerated with oxygen and light, you should always store foods that contain vitamin A dark and best in the refrigerator. When cooking, the loss of vitamin A depending on the cooking time between 10 and 30 percent.
Vitamin A in pregnancy
During pregnancy, the demand for vitamin A in women is slightly higher than usual. It is particularly important at this time that mother and child are adequately supplied with vitamin A, as it has an important influence on the development of the child.
However, one should also be careful during pregnancy, not to dose high vitamin A, as it can come in an overdose to birth defects in the child. It can cause growth disorders, liver damage, damage to the eyes as well as skin changes.
Since especially liver contains large amounts of vitamin A, it is not recommended to consume it during pregnancy. Likewise, one should not resort to dietary supplements that contain vitamin A, such as vitamin A tablets. The use of provitamin A, however, is considered harmless during pregnancy.
Hypovitaminosis: lack of vitamin A.
If there is not enough vitamin A in the body, it can lead to hypovitaminosis. The risk group for vitamin A deficiency includes the elderly, young women, infectious children, and premature babies. Typical symptoms of hypovitaminosis are:
- Increased susceptibility to infections
- Reduced visual acuity
- Dryness of hair, nails, eyes and hair as well as hair loss
- Impaired sense of smell and touch as well as reduced appetite
A vitamin A deficiency can increase the risk of arteriosclerosis and possible sequelae, cancer in organs that have a mucous membrane, fertility disorders and kidney stones.
Just as numerous as the possible consequences are the causes of vitamin A deficiency. These include stress, inflammation and surgery, serious illnesses such as cancer, arthritis or AIDS, environmental toxins, smoking, alcohol and strong sunlight. In addition, laxatives and cholesterol lowering drugs worsen the absorption of vitamin A, while consuming certain sleep aids depletes the vitamin A reserves in the liver. In addition, people who have diabetes or hyperthyroidism have problems turning vitamin C into plant-derived carotenoids.
If vitamin A deficiency is present, foods rich in the vitamin should be consumed more frequently. In addition, if a disease is the cause of vitamin A deficiency, the disease should be treated.
Hypervitaminosis: overdose of vitamin A.
As with other fat-soluble vitamins, an overdose of vitamin A is harmful to your health. However, an overdose can only be caused by the intake of too much vitamin A, ie by too much animal food, but not by too much provitamin A. Because if we ingest too many carotenoids, our body shuts down the conversion to vitamin A. By ingesting large amounts of carotenoids, however, it can lead to a yellowing of the skin.
In case of overdose, a distinction is made between an acute hypervitaminosis, which results from the intake of a large amount of vitamin A within a short time, and a chronic hypervitaminosis, which occurs through the ingestion of too much vitamin A over a longer period of time. For example, an acute overdose of vitamin A can be caused by large amounts of fish or seal liver. It can cause symptoms like headache, dizziness and vomiting. If vitamin A is administered in large quantities over several weeks, it can also lead to a complete loss of body hair.
If higher doses of vitamin A are taken over a longer period of time, this can have even more serious consequences: it can lead to increased intracranial pressure, excess calcium with consequences such as high blood pressure and kidney failure, growth of the periosteum and an enlargement of the liver and spleen. Over years too high a dose of vitamin A, symptoms of intoxication, which can also lead to death.