Vitamin A, or retinol, is an essential nutrient for good daily health, although its role is often unknown.
So, what is it really for: Eye health, skin health, iron metabolism ?
In this article, we will review all the information relating to this vitamin and we will answer the following questions:
- What are the benefits and role of vitamin A?
- Is there a risk of deficiency?
- What are the richest foods?
What is vitamin A?
Vitamin A is an organic substance essential to our metabolism. However, it was only formally identified late.
The first vitamin identified
Vitamin A is the first vitamin to have been identified , which explains the attribution of the letter A.
In 1913, several American researchers including Elmer McCollum and Marguerite Davis provided proof of the existence of a fat-soluble substance essential for human health. Indeed, they demonstrate that animals deprived of the latter develop eye infections. They then named this substance fat-soluble A, literally in French, liposoluble A.
However, it was not until 1931 that the Swiss researcher Karrer managed to isolate the molecule and define its chemical structure.
A fat-soluble organic compound
Vitamin A is an organic compound without any energy value . It is not synthesized by the human body but plays a very important role.
Vitamin A is said to be fat-soluble, meaning it dissolves in fatty substances but not in water. Furthermore, it is resistant to heat and acidity. On the other hand, it oxidizes in air and is destroyed by light.
These characteristics are important since it allows its absorption by the small intestine at the same time as lipids. It is then stored mainly in the liver, but also in the epidermis and in the retina. It is also because it was isolated in this membrane of the eyeball that it is called retinol.
However, vitamin A does not represent a single chemical molecule, but a group of organic compounds with similar characteristics:
- Retinol and its derivatives for the animal world;
- Provitamin carotenoids for the plant world. They are provitamins A, that is to say precursors of vitamin A. The best known representatives are lycopene, beta-carotene and zeaxanthin.
What is the role of vitamin A?
Vitamin A is involved in numerous metabolic reactions including:
- The regulation of genome expression: a key role in activating or repressing genes throughout our lives. Vitamin A participates in particular in embryonic development, cell growth and tissue renewal (epidermis, intestine, mucous membranes, etc.);
- Twilight vision: retinaldehyde is one of the forms of vitamin A. This photosensitive protein pigment is present in the rod cells of the retina. These are responsible for twilight vision. Concretely, vitamin A undergoes different chemical transformations depending on the light. These same transformations generate an electrical impulse interpreted by the brain;
- The normal functioning of the immune system by allowing the differentiation and growth of cells;
- An anti-oxidant function: vitamin A helps neutralize free radicals.
What are the benefits of vitamin A?
Vitamin A is an essential nutrient throughout life for good health. Its benefits are numerous, in particular on:
- Protection of the eyes and the lens, the alteration of which can lead to cataracts;
- AMD : Age-related macular degeneration (AMD) affects many patients over 50 years old. It results in loss of vision in the central part of the retina. The preventive role of vitamin A in this form of limited blindness has been demonstrated;
- Action against cellular aging due to free radicals: stress, anxiety, fatigue, an unbalanced diet or prolonged exposure to the sun are all factors favoring the formation of free radicals. Vitamin A helps to trap these free radicals, and therefore prevent premature aging of cells;
- Stimulation of the immune system .
Finally, certain publications credit it with an action against cancer. To date, a clear link with possible remissions has not been established.
On the other hand, an excess of retinol in pregnant women at the start of pregnancy can cause fetal malformations, a risk which does not exist with carotenoids.
What are the daily requirements for vitamin A?
Vitamin A intakes are generally expressed in micrograms EAR (retinol activity equivalent) or ER (retinol equivalent).
According to ANSES (National Food Safety Agency), the daily nutritional references for vitamin A are:
- 650 µg of RE for a woman;
- 750 µg of RE for a man.
With regard to children, these same needs are being reassessed by ANSES.
What are the symptoms of a deficiency?
Severe vitamin A deficiency is uncommon in Western countries . However, certain symptoms may be linked to a deficiency:
- A decrease in visual acuity when night falls;
- Less resistance to diseases, bacteria and viruses.
However, it is worth pointing out that these two symptoms are not specific to vitamin A deficiency.
To determine the exact origin, it is imperative to consult a health professional.
What foods are rich in vitamin A?
Like other essential nutrients, vitamin A cannot be synthesized by the human body . Only a balanced diet can meet our daily needs.
However, certain foods have higher concentrations of retinol equivalent.
Among the richest foods, we find in particular (in μg RE per 100 g):
- Cod liver oil: 30,000 μg;
- Beef liver: 9442 µg;
- Parsley: 5360 µg;
- Country or liver pâté: 4200 μg;
- Chicken offal: from 1,750 to 4,000 µg;
- Raw carrot: 1380 µg;
- Swiss chard: 3650 mcg;
- Dried apricots: 2160 µg;
- Lettuce: 2000 mcg;
- Sweet potato: 1100 µg;
- Butter: 800 μg;
- Cooked carrot: 556 µg;
- Crème fraîche: 390 μg;
- Marinated herring: 260 µg;
- Cheeses: 245 to 350 μg;
- Egg: 260 μg.
Why food supplements rich in vitamin A?
It may happen in certain situations that the daily vitamin A requirements are not completely covered . This can be caused by an unbalanced diet, taking certain medications or intestinal disorders.
Taking food supplements like our Multivitamin and Mineral formula is then an interesting alternative. Note: In the ARGALYS Multi formula, Vitamin A is provided in a moderate proportion, sufficient to correct an unbalanced diet (50% of the RDA/capsule), but above all: in the form of Carotenoids so as to present no risk for the pregnant women (and their babies), this is an important point of vigilance when choosing vitamin supplementation.
- EFSA (2015 VA) Panel on Dietetic Products, Nutrition and Allergies (NDA); Scientific Opinion on dietary Reference Values for vitamin A. The EFSA Journal 13 (3): 4028. https://efsa.onlinelibrary.wiley.com/doi/epdf/10.2903/j.efsa.2015.4028 , accessed September 14, 2018.
- Anses (2016) Updating the PNNS benchmarks: Development of nutritional references. Collective expert reports. Scientific edition. https://www.anses.fr/fr/system/files/NUT2012SA0103Ra-2.pdf , accessed September 11, 2018.