Vitamin A, or retinol, is one of the essential fat-soluble vitamins for the body.
It is found as retinol in mammals and as provitamin A (beta-carotene) in plants.
Its actions in the body include maintaining visual acuity and strengthening the immune system.
Vitamin A characteristics
- Fat-soluble vitamin important for vision and the immune system
- Found in certain plants as provitamin A (beta-carotene)
- Found in large quantities in organ meats in the form of retinol
- Beta-carotene is a powerful antioxidant and promotes skin pigmentation.
- Excess beta-carotene can have adverse health effects
Benefits of vitamin A
Vitamin A, beta-carotene, retinol and provitamin A: what are the differences?
In the human and animal body, vitamin A is found in the form of retinol, retinal or even retinoic acid.
Foods of animal origin therefore contain vitamin A in the form of retinol.
In plant foods, vitamin A is found in the form of carotenes, which are precursors of vitamin A, called provitamin A.
In this sense, beta-carotene is a provitamin A.
Vitamin A plays an important role in the quality of your vision.
It enables nerve impulses to be triggered at the level of the optic nerves.
Adequate vitamin A intake therefore reduces the risk of cataracts and macular degeneration.
Antioxidant
Carotenes, and beta-carotene in particular, are molecules with powerful antioxidant properties.
In the body, antioxidants help fight cell ageing and oxidative stress.
In other words, they neutralise the damage caused by free radicals and help maintain a healthy body and strong immune system.
Vitamin A and the skin
Retinol is involved in the differentiation and renewal of cells in the body, particularly the skin and mucous membranes.
We also often emphasise the benefits of carotene-rich foods on skin quality.
In fact, vitamin A is a precursor of melanin, which is responsible for skin pigmentation.
So a good intake of vitamin A and beta-carotene prepares the skin for the sun, protects skin cells from external aggression and promotes skin renewal.
Foods rich in vitamin A
In the diet, different foods are sources of retinol or carotenes.
Carotenes are mainly found in orange fruits and vegetables and green leafy vegetables, while retinol is mainly found in organ meats.
Food sources of vitamin A
- Turkey offal
- Beef liver
- Chicken offal
- Carrot juice
- Sweet potato
- Squash
- Cooked carrots
- Cooked spinach
- Boiled cabbage
- Cooked beet leaves
- Cooked turnips
- Lettuce (romaine, mesclun, corn salad)
- Herring
- Dandelion leaves
- Bowler hat
- Cooked bok choi or bok choy
- Red bell pepper
- Tomato or vegetable juice
Daily value of vitamin A
Recommended dietary intake
- Infants 0-6 months = 400mcg
- Infants 7-12 months = 500mcg
- Infants 1 to 3 years = 300mcg
- Children 4 to 8 years = 400mcg
- Boys 9 to 13 years = 600mcg
- Girls 9 to 13 years = 600mcg
- Boys 14 to 18 years = 900mcg
- Girls from 14 to 18 years = 700mcg
- Men from 19 to 50 years = 900mcg
- Women aged 19 to 50 = 700mcg
- Men aged 50 and over = 900mcg
- Women aged 50 and over = 700mcg
- Pregnant women = 770 mcg
- Women who are breastfeeding = 1300 mcg
Food supplements containing beta-carotene or vitamin A
Many dietary supplements contain vitamin A or its precursors (including beta-carotene).
Vitamin A supplementation may be indicated to prevent or treat eye diseases (retinitis, macular degeneration, cataracts, etc.).
In addition, these supplements are particularly appreciated for their antioxidant capacity, which helps to support the immune system and prevent certain diseases.
Finally, as summer approaches, beta-carotene is widely used to activate melanin synthesis and promote tanning.
But be careful: if taking vitamin A has little effect, taking beta-carotene can be dangerous in the long term.
Consult your doctor before considering supplementation.
Consequences of vitamin A deficiency
Vitamin A deficiency is much more common than you might think, especially in underserved populations.
It mainly causes vision problems, ranging from simple corneal changes to total blindness.
Vitamin A deficiency can also lead to a weakened immune system and increased susceptibility to infection.
Consequences of excess vitamin A
Vitamin A is stored in the liver, and excess can lead to hepatomegaly (enlarged liver) and various digestive problems (nausea, diarrhoea, etc.).
On the skin, an overdose may cause irritation and itching.
In children there is a risk of excessive thickening of bone tissue.
In pregnant women, an excess of vitamin A can cause foetal malformations.
Fortunately, except in exceptional cases (liver disease, excessive intake of supplements, etc.), excessive intake is extremely rare.
Interactions with other nutrients
Lipids have a beneficial effect on the absorption of vitamin A, regardless of its form (retinol or carotenes).
It is therefore recommended to consume foods rich in vitamin A as part of a complete meal.
In addition, the antioxidant effect of beta-carotene is increased in the presence of other antioxidant molecules such as vitamin C, vitamin E, selenium or even zinc.
Smokers are advised not to take beta-carotene supplements.
In fact, the combination of provitamin A and certain molecules found in tobacco would increase the risk of developing lung and stomach cancer.
Chemical properties
Vitamin A is a fat-soluble vitamin.
In mammals, it exists in several forms: retinol, retinal, retinoic acid, etc.
Plants contain carotenes, including beta-carotene, which are precursors of vitamin A.
One molecule of beta-carotene produces two molecules of vitamin A.
The molecular formula of beta-carotene is C40H56 and its molecular weight is 536.8726 g/mol.
This is the most common form of carotene and is also a powerful antioxidant and an additive widely used by the food industry to colour and prevent oxidation.
