english: vitamina a acidoverview vitamins
Occurrence and structure of vitamin A
Beta-carotene, the precursor of vitamin A, can be split into two molecules retinal, which consist of four isoprene units and a simple ring system. Vitamin A is supplied via food and is particularly contained in animal food sources. Liver contains a particularly large amount of vitamin A, since the fat-soluble vitamin is stored in this organ.
Other sources are milk and dairy products such as butter, eggs (especially egg yolk) and fish. A vegetarian or vegan diet can also cover the requirements. In vegetable sources above all the so-called Provitamin A (β-Carotin) is contained, which the body can convert into Vitamin A.
The Provitamin A is contained in particular in carrots. Further vegetable food with a high Provitamin A content are apricots, green cabbage, spinach and pumpkin. Provitamin A offers the advantage that the body converts it into vitamin A only when needed, so there is no risk of oversupply.
However, an oversupply from animal foods is also rather rare. And once again briefly summarizing the occurrence of vitamin A:
- Vegetable (carrots, oranges, spinach, brcolli, green cabbage)
- Animal (liver products, fish, egg yolk, milk products)
Retinal is essential for the visual process. Here it is a part of the receptor complex that is sensitive to light.
The structure of the retinal is changed by light incidence, which leads to the activation of a G-protein. In the end, this chain of reactions results in the perception of light as such. Retinal can be transformed into retinol and retinoic acid. The former protects epithelia (inner and outer body surfaces), the latter is involved in gene expression and thus has an influence on development and growth.
Vitamin A deficiency
First symptoms are mostly night blindness. If it is more pronounced, the cornea (the cornea that contributes the most to light refraction and thus to vision) may be cornified. This is the most common cause of blindness in children in underdeveloped countries!
Signs of this are dizziness, vomiting, headaches and – if it persists for a long time – hair loss and skin dehydration. Vitamin A is important for normal skin function. Accordingly, a deficiency has a variety of effects on our largest organ, but these are unspecific in themselves.
This means that other causes are also possible and that the overall picture must always be considered. One of the possible consequences of a vitamin A deficiency is skin dryness due to reduced sweat and sebum production. It also leads to an increased formation of wrinkles and a decrease in skin elasticity.
Brittle nails and hair loss can also be a consequence. In addition to dry mucous membranes, a lack of vitamin A also increases the risk of cancer. Reduced saliva production also results in a dry mouth and increased susceptibility to inflammation of teeth and gums.
Since vitamin A is particularly important for the eyes and our sense of sight, a deficiency often shows up here most quickly. Typically, this leads to so-called night blindness. This means that one can see much worse in the dark than before, or in comparison to healthy people without vitamin A deficiency.
The cause is impaired light-dark vision. Besides the visual acuity decreases. One sees thus more blurred and can recognize faces more badly and gets problems with the In addition it comes to the drying up of the tear glands and the connective skins and thus to dry, itching eyes.
In addition, pale and horny spots can form. Furthermore, ulcers can form on the cornea. If a vitamin A deficiency is not compensated, blindness may ultimately result.
If a vitamin A deficiency is not compensated, blindness may ultimately result. A vitamin A deficiency is one of many possible causes of hair loss. If there are symptoms in the eyes and skin that coincide with a vitamin A deficiency, the suspicion is confirmed.
However, evidence can only be provided by a blood test and the professional assessment of a doctor.If only hair loss is noticeable, a vitamin A deficiency as a cause is rather unlikely. A clarification of what the cause of hair loss is can also be done by a doctor. It is a widespread condition, especially in men but also in many older women.
The cause is usually rather hormonal problems. Under no circumstances should one attempt to treat hair loss with vitamin A products. If there is no deficiency, there is a risk of oversupply with dangerous consequences, for example for the liver.