Vitamin A or axerophthol is a fat-soluble vitamin.
It is in its alcoholic or retinol form (vitamin A1) that vitamin A is transported in plasma, cerebrospinal fluid, eye fluids and urine, in association with prealbumin.
Retinol is one of three available forms of vitamin A, along with retinal andretinoic acid.
As the body is unable to synthesize this vitamin naturally, it must obtain it from the diet.
However, vitamin A is teratogenic, and therefore contraindicated for pregnant women.
Vitamin A is supplied to us in the form of carotene or provitamin A via :
Good to know : Vitamin A or retinol and beta-carotene are not very sensitive to cooking. They can, however, be degraded by oxidation, which is why it's a good idea to store foods in a cool place, away from air and light.
The recommended daily allowance is 800 micrograms for men and 600 micrograms for women. A balanced diet covers vitamin A requirements.
Daily vitamin A requirements are expressed in retinol equivalents or international units. They vary according to age and sex:
Vitamin A comes in the form of tablets, soft capsules, oily solutions or products to be applied to the skin.
Vitamin A doses are expressed in micrograms of retinol, retinol equivalents (RE) or international units (IU):
1 µg retinol = 1 RE = 3.3 IU.
In 2012, the European health authorities (EFSA, European Food Safety Authority and the European Commission) deemed that vitamin A-based food supplements can contribute to the above actions if, and only if, these products contain at least 120 micrograms of vitamin A (retinol) per 100 g, 100 ml or per package if the product contains only one portion.
Food supplements provide an average of 1,500 micrograms per day. This quantity corresponds to the maximum daily dose that a pregnant woman can ingest.
European health authorities' decision on vitamin A
In 2012, the European health authorities (EFSA, European Food Safety Authority and the European Commission) gave their opinion on certain health claims for foods and dietary supplements containing vitamin A (retinol). After examining the scientific data, they concluded that these products can claim to contribute to :
Vitamin A-rich nutritional supplements can make these health claims if, and only if, they contain at least 120 micrograms of vitamin A (retinol) per 100 g, 100 ml, or per package if the product contains only one portion.
Vitamin A deficiency can be caused by low dietary intake, malabsorption, or increased utilization or excretion due to common diseases.
Vitamin A deficiency causes keratinizing metaplasia of the epithelia (production of a tissue different from that usually made by the lining tissues, and impregnated with keratin), which can cause:
In underdeveloped countries, vitamin A deficiency is the leading cause of blindness.
On the other hand, vitamin A hypervitaminosis can cause :
As you can see, vitamin A promotes blood circulation and visual acuity. It prevents or reduces infections, oxidation, acne, hair loss, insomnia and weight loss, and is used as a supplement in many cancers. This vitamin is involved in the formation of rhodopsin, a pigment involved in twilight vision and the synthesis of glycoproteins.
Carotenoids are precursors of vitamin A, which helps protect the immune system. Plant sources include carrots, apricots, peaches, peppers, spinach, lettuce, tomatoes, sweet potatoes, broccoli, squash, apricots and, above all, spirulina Arthrospira platensis.
Smokers should not take vitamin A or beta-carotene supplements: smokers taking vitamin A supplements may be associated with an increased risk of lung cancer.
During pregnancy, excess vitamin A intake can cause fetal malformations. For this reason, pregnant women should avoid fortifying their diet with vitamin A and carotenoids; they should limit themselves to those contained in their food. The same applies to nursing mothers.
For more information, ask your pharmacist.
