Vitamin A is a fat-soluble vitamin. It is important for healthy cells, skin, and eyes. Learn all about vitamin A, its sources, and the best dosage.
Table of contents
1. What is vitamin A?
Vitamin A, like vitamins E, D, and K, is a fat-soluble vitamin . It is also known as retinol . Its precursors also include provitamin A , which is found as beta-carotene, particularly in colorful plants and vegetables.
Beta-carotene belongs to the so-called carotenoids . These are secondary plant pigments that also possess antioxidant properties . This means they can protect our bodies against oxidative stress .
As a provitamin, it is only converted into vitamin A after absorption into the body. Vitamin A fulfills many important functions within our body: It is necessary for the formation and development of our cells and tissue structures, such as skin and mucous membranes.
Furthermore, vitamin A plays a central role in vision . Light-dark vision, in particular, is highly dependent on vitamin A levels [1].
Like all fat-soluble vitamins, it is not eliminated through metabolism but can be stored in the body . The liver serves as the primary storage site. However, the vitamin is always absorbed through the small intestine .
2. What effect does vitamin A have?
The function and effect of vitamin A lies, on the one hand, in the maintenance of normal skin and mucous membranes . On the other hand, vitamin A also makes a significant contribution to maintaining normal vision .
It is also essential for maintaining the normal function of the immune system and normal iron metabolism [2].
In its retinal form, it contributes to the maintenance of normal vision. As it travels through the bloodstream, vitamin A binds to various proteins.
This creates a specific biochemical process that results in the formation of the pigment rhodopsin. This pigment is also known as "visual purple" due to its characteristic color and function.
Once it reaches the rods of the eye, the new rhodopsin protein then transmits nerve impulses to the brain, which in turn enable the process of vision.
Furthermore, vitamin A is involved in the production of testosterone . This process takes place in the testes, where many male sex hormones are produced. The development of male sperm cells cannot occur without sufficient vitamin A.
Due to its relevance for cell development, the vitamin also plays a crucial role for women during pregnancy and for fetal growth . Vitamin A is needed for both placental formation and fetal maturation.
This also explains the effect of vitamin A on the elasticity of the skin and mucous membranes. These, like the placenta and fetus, consist of cellular elements that must be renewed repeatedly throughout life.
3. Which foods contain vitamin A?
Foods rich in vitamin A are almost always of animal origin . Only a few plants contain retinol in addition to beta-carotene. Calf's liver is considered a particularly reliable source of vitamin A, with 39 mg/100 g.
Liver sausage and sea fish are also good options , but at approximately 8.9 mg/100 g, they contain significantly less vitamin A than liver. Good sources of beta-carotene, however, include tomatoes , broccoli , apricots , parsley , dill , and savoy cabbage . Carrots are also among these.
A good indicator that a vegetable contains a lot of beta-carotene is the intensity of its color : if it is very red , very green or very orange , there is a good chance that it contains this important vitamin precursor .
To ensure that carotenoids can be better utilized , it is worth including a solid source of fat in the same meal.
Fortunately, it doesn't have to be particularly complicated: in most cases, it's enough to fry your vegetables in a high-quality vegetable fat .
However, you shouldn't roast your vegetables for too long: exposure to heat and light can lead to significant loss of vitamin A. Therefore, it's best to eat vegetables raw, especially immediately after purchase.
4. How much vitamin A is healthy?
According to the Food and Drug Administration, the recommended daily intake of vitamin A for adult men is approximately 1.0 mg . For adult women, slightly less is sufficient – 0.8 mg per day is assumed.
An exception , however, is pregnancy , where there is a slightly increased need of 1.1 mg per day due to the numerous growth processes of mother and child .
Even after this, new mothers must ensure they consume enough vitamin A: breastfeeding mothers are estimated to need even more at 1.5 mg per day .
Despite the increased need during pregnancy, some caution is still advised . Especially in pregnant women, not only a deficiency but also an overdose of vital nutrients can have unpleasant consequences .
5. Vitamin A deficiency and overdose
Vitamin A deficiency is actually very rare in Germany . This is partly due to the fact that most people here have good access to nutrient-rich foods.
So, for now, you don't need to worry too much about a vitamin A deficiency. Don't forget: Even if you don't reach the recommended intake, vitamin A is stored in the body as a fat-soluble vitamin.
This alone makes it significantly more difficult to develop a deficiency. The typical cause of a vitamin A deficiency is almost always malnutrition or undernutrition [3].
However, since the vitamin is absorbed in the small intestine and stored in the liver , diseases of these organs can also be a cause .
The main symptoms of a vitamin A deficiency are:
- very dry skin
- Irritated or dry mucous membranes
- Visual disturbances, especially regarding light-dark vision and
- severe night blindness.
Symptoms of an overdose, however, are:
- Headache
- nausea
- Sleep disorders
- Loss of appetite
- dry skin and mucous membranes
- Hair loss
- Bones become more brittle.
In the event of an overdose , very similar problems to those caused by a deficiency can occur, particularly with regard to the skin and mucous membranes.
Some caution is also advised with regard to provitamin A, or beta-carotene. Although an overdose is difficult to guarantee, long-term overdose may possibly increase the risk of lung cancer [4].
6. Conclusion
Vitamin A is an absolutely essential micronutrient. It plays a central role in our cells as well as our skin, our eyesight, and our mucous membranes.
The maintenance of normal immune system function, as well as the production of testosterone and the maturation of fetuses, could not take place without vitamin A.
With plenty of colorful vegetables, you can easily ensure a supply of the provitamin A beta-carotene, which can then be converted into vitamin A. If you like, you can also eat animal sources such as liver, liver sausage, or sea fish to get vitamin A in its ready-made form.
Vitamin A deficiency is very rare in this country. This is due, on the one hand, to the good food supply and, on the other, to the fact that vitamin A, as a fat-soluble vitamin, can be stored in the body.
By consuming a little extra fat, you can also help your body better utilize the vitamin A you consume. Pregnant women, in particular, should be careful of a deficiency or overdose.
They require significantly more vitamin A, as it's so important for fetal and early childhood growth processes. However, with a little careful cooking, you don't have to worry about it in most cases.
7. Sources
[1] Gilbert, C. (2013), What is vitamin A and why do we need it, Community Eye Health Journal, Volume 26, Issue 84, p. 65, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3936685/.
[2] Huang, Z.; Liu, Z.; [...]; Zheng, SG (2018), Role of Vitamin A in the Immune System, Journal of Clinical Medicine, Volume 7, Issue 9, p. 258, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6162863/.
[3] Kraemer, K.; Gilbert, C. (2013), Do vitamin A deficiency and undernutrition still matter, Community Eye Health Journal, Volume 26, Issue 84, p. 61-63, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3936683/.
[4] Olsen, J.M.; Ameer, AM; Goyal, A. (2020), Vitamin A Toxicity, StatPearls, https://www.ncbi.nlm.nih.gov/books/NBK532916/.
