Vitamin A: benefits, dosage, contraindications
Other name(s)
Beta-Carotene, Retinol
Family or group:
Vitamins
Indications
Scoring methodology
EFSA approval.
Vitamin A deficiency ✪✪✪✪✪
Although most vitamin A deficiencies are not severe enough to be associated with defined and observable symptoms, sources of stress, such as measles, pneumonia, or diarrhea, can further reduce its level and lead to severe disease. Indeed, vitamin A deficiency can impair vision, on a spectrum ranging from reduced night vision to blindness. The nutritional reference values for the population (NRV) are proposed to cover the "normal" nutritional needs for a population. The NRVs for vitamin A in adults were updated in 2016. They are 750 µg RE per day for men (vitamin A activity is expressed relative to that of retinol according to a retinol equivalent (RE) system) and 650 µg for women.
Posologie
Oral
750 - 3000 µg
Adults
Vitamin A deficiency and xerophthalmia among school-aged children in Southeastern Asia.
Chronic low intakes of vitamin A-rich foods in households with xerophthalmic children: a case-control study in Nepal.
Prevalence of xerophthalmia and efficacy of vitamin A prophylaxis in preventing xerophthalmia co-existing with malnutrition in rural Indian children.
Vitamin A & provitamin A carotenoids Overview, food sources and nutritional requirements
Skin health ✪✪✪✪✪
Vitamin A is required for the integrity of mucous membranes and epithelial surfaces. Vitamin A deficiency leads to keratinization of epithelial surfaces with dry skin.
Posologie
Oral
750 - 3000 µg
Adults
Eye health ✪✪✪✪✪
Vitamin A contributes to normal vision. Indeed, it is necessary for the maintenance of the epithelium of the conjunctiva and the cornea. It is also necessary for epithelial RNA synthesis. Vitamin A deficiency is one of the leading causes of blindness in developing countries. When intake is insufficient, night vision becomes difficult, the cornea thickens and then dies.
Posologie
Oral
750 - 3000 µg
Adults
Chronic low intakes of vitamin A-rich foods in households with xerophthalmic children: a case-control study in Nepal.
Prevalence of xerophthalmia and efficacy of vitamin A prophylaxis in preventing xerophthalmia co-existing with malnutrition in rural Indian children.
DIETARY SUPPLEMENT: VITAMIN A
Fetal development ✪✪✪✪✪
Vitamin A plays an important role in neural development and is also involved in the development of the limbs, lungs, heart, eyes and ears. However, an excess of vitamin A is teratogenic, causing malformations of the central nervous system, the craniofacial region, the cardiovascular system and the thymus.
Posologie
Oral
700 - 3000 µg
Pregnant women
Wrinkles ✪✪✪✪✪
The topical application of a vitamin A–based night cream appears to reliably reduce the appearance of fine lines. To achieve beneficial effects on the skin, the concentration of retinol in the cream must be substantial (at least 0.3%). Treatment begins with two applications per week, progressing to once-daily application.
Posologie
Topical
Adults
cream
AMD ✪✪✪✪✪
Supplementation with antioxidants including vitamins A (15 mg), C (500 mg), E (400 IU), and zinc (80 mg) reduces the risk of vision loss by 27% and slows disease progression.
Posologie
Oral
15 mg
10 - years
Adults
Long-term effects of vitamins C and E, ß-carotene, and zinc on age-related macular degeneration: AREDS report no. 35.
Age-Related Eye Disease Study Research Group. Potential public health impact of age-related eye disease study results: AREDS report no. 11.
Multiple sclerosis ✪✪✪✪✪
Vitamin A may reduce fatigue related to multiple sclerosis. A daily dose of 25,000 IU as retinyl palmitate for 6 months, followed by 10,000 IU per day for 6 months, may relieve symptoms in affected patients.
Posologie
Oral
10,000 - 25,000 IU
12 - months
Adults
Breast cancer ✪✪✪✪✪
Epidemiological data show a link between high dietary vitamin A intake and a reduced risk of breast cancer in premenopausal women with a family history of breast cancer. However, it is unknown whether vitamin A supplementation provides the same benefits. It should be noted that a daily dose of 700 mcg (equivalent to 2300 UI) is recommended to help prevent possible breast cancer.
Posologie
Oral
2300 - 2300 UI
Women
Rheumatoid arthritis ✪✪✪✪✪
Preliminary clinical research has shown that taking a supplement containing astaxanthin (4 mg), lutein (40 µg), vitamin A (65 UI), vitamin E (50 UI), and safflower oil (460 mg), three times a day for 8 weeks, reduces pain and increases satisfaction by approximately 40% compared with placebo in patients with rheumatoid arthritis.
Posologie
Oral
195 UI
8 weeks
Adults
Synergies
Properties
Essential
Vitamin A is important for the health of mucous membranes, skin, and eyes. It is generally present in sufficient amounts in the body. A deficiency can occur due to abnormal storage and transport of vitamin A in affected individuals, protein deficiency, diabetes mellitus, hyperthyroidism, fever, liver disease, and cystic fibrosis. In vulnerable groups (children and the elderly), the consequences of moderate vitamin A deficiencies, particularly in relation to infectious conditions, can be concerning. Decreased visual acuity, especially in dim light (night vision), is one of the earliest apparent signs of vitamin A deficiency in humans.
Usages associés
Dermatologic effect
A carboxylic acid ester of retinol known as all-trans retinoic acid (ATRA), also known by several names such as tretinoin, is the most commonly used form of vitamin A. In culture, ATRA has been found to increase the synthesis (anabolism) of collagen and to inhibit the enzymes responsible for collagen degradation, collagenase and gelatinase. Additionally, ATRA reduces collagen degradation caused by ultraviolet radiation.
Usages associés
Vision
Vitamin A is necessary for the maintenance of the conjunctival and corneal epithelium. It is also necessary for epithelial RNA synthesis. nnIn the retina, rhodopsin (visual purple), a photosensitive protein pigment present in the photoreceptor cells of the retina known as rods, is required for the transduction of light into neural signals that produce vision. It is formed from a transmembrane protein, opsin, to which retinal binds; retinal is an aldehyde of vitamin A or beta-carotene.nnThe most specific indicator of vitamin A deficiency is xerophthalmia, which initially presents as night blindness that, if left untreated, progresses to total loss of vision.nn
Usages associés
Immunomodulator
Vitamin A is important for immune function. Retinoic acid is necessary to maintain sufficient levels of natural killer cells. Studies suggest that retinoic acid can increase the production of cytokines, such as interleukin 1 (IL-1). In addition, the growth, differentiation, and activation of B lymphocytes depend on retinol.nnOn the other hand, retinoic acid can suppress the proliferation of pathogenic T lymphocytes present in multiple sclerosis and increase the production of regulatory cells that modulate the immune system. nn
Usages associés
Anti-inflammatory
Retinoic acid has been shown to stimulate anti-inflammatory effects, reduce the production of inflammatory cytokines, and alter the levels of retinoic acid receptors on immune cells that secrete anti-inflammatory cytokines.nn
Usages associés
Anticancer
Retinoids can help prevent cancer by inducing tumor suppressor genes called retinoic acid receptors (RAR) that are absent in many malignant tumor cells, probably due to gene methylation. Once demethylated, it can be induced by RAR to function and inhibit the growth of cancer cells. Vitamin A acts as an antioxidant and a free radical scavenger. Thus, it reduces oxidative stress and stimulates immune function in cases of cancer.
Usages associés
Antioxidant
Vitamin A has free radical-scavenging properties and is generally considered an antioxidant molecule. Vitamin A bound to protein kinase C is an essential cofactor in the redox activation of the mitochondrial signaling pathway. Moreover, in vivo evidence has shown that, at high doses, vitamin A has a pro-oxidant effect with mitochondrial redox dysfunction and increased oxidative stress in the brains of rats.
Safe dosage
Adults 18 years and older: 800 µg - 3000 µg
The values refer to vitamin A in the form of retinol, retinyl esters and provitamin A carotenoids. RE: retinol equivalent. The provitamin A carotenoids have lower bioavailability than retinol. To account for these differences, REs were introduced and defined as 1 μg RE = 1 μg retinol = 6 μg β-carotene = 12 μg of other provitamin A carotenoids.
Infant up to 12 months: 250 µg
The values refer to vitamin A in the form of retinol, retinyl esters and provitamin A carotenoids. RE: retinol equivalent. The provitamin A carotenoids have lower bioavailability than retinol. To account for these differences, REs were introduced and defined as 1 μg RE = 1 μg retinol = 6 μg β-carotene = 12 μg of other provitamin A carotenoids.
Child aged 1 to 3 years: 250 µg - 800 µg
The values refer to vitamin A in the form of retinol, retinyl esters and provitamin A carotenoids. RE: retinol equivalent. The provitamin A carotenoids have lower bioavailability than retinol. To account for these differences, REs were introduced and defined as 1 μg RE = 1 μg retinol = 6 μg β-carotene = 12 μg of other provitamin A carotenoids.
Child aged 4 to 6 years: 300 µg - 1100 µg
The values refer to vitamin A in the form of retinol, retinyl esters and provitamin A carotenoids. RE: retinol equivalent. Provitamin A carotenoids have lower bioavailability than retinol. To account for these differences, REs have been introduced and are defined as 1 μg RE = 1 μg retinol = 6 μg β-carotene = 12 μg of other carotenoids with provitamin A activity.
Child aged 7 to 10 years: 400 µg - 1500 µg
The values refer to vitamin A in the form of retinol, retinyl esters and provitamin A carotenoids. RE: retinol equivalent. Provitamin A carotenoids have lower bioavailability than retinol. To account for these differences, REs have been introduced and are defined as 1 μg RE = 1 μg retinol = 6 μg β-carotene = 12 μg of other carotenoids with provitamin A activity.
Child aged 15 to 17 years: 750 µg - 2600 µg
The values refer to vitamin A in the form of retinol, retinyl esters and provitamin A carotenoids. RE: retinol equivalent. Provitamin A carotenoids have lower bioavailability than retinol. To account for these differences, REs have been introduced and are defined as 1 μg RE = 1 μg retinol = 6 μg β-carotene = 12 μg of other carotenoids with provitamin A activity.
Child aged 11 to 14 years: 600 µg - 2000 µg
The values refer to vitamin A in the form of retinol, retinyl esters and provitamin A carotenoids. RE: retinol equivalent. Provitamin A carotenoids have lower bioavailability than retinol. To account for these differences, REs have been introduced and are defined as 1 μg RE = 1 μg retinol = 6 μg β-carotene = 12 μg of other carotenoids with provitamin A activity.
Women in menopause aged 50 and older: 650 µg
Values refer to vitamin A in the form of retinol, retinyl esters and provitamin A carotenoids. RE: retinol equivalent. Provitamin A carotenoids have lower bioavailability than retinol. To account for these differences, RE were introduced and defined as 1 μg RE = 1 μg retinol = 6 μg β-carotene = 12 μg of other provitamin A carotenoids.
Pregnant women aged 18 and older: 700 µg - 3000 µg
Values refer to vitamin A in the form of retinol, retinyl esters and provitamin A carotenoids. RE: retinol equivalent. Provitamin A carotenoids have lower bioavailability than retinol. To account for these differences, RE were introduced and defined as 1 μg RE = 1 μg retinol = 6 μg β-carotene = 12 μg of other provitamin A carotenoids.
Lactating women aged 18 and older: 1300 µg - 3000 µg
Values refer to vitamin A in the form of retinol, retinyl esters and provitamin A carotenoids. RE: retinol equivalent. Provitamin A carotenoids have lower bioavailability than retinol. To account for these differences, RE were introduced and defined as 1 μg RE = 1 μg retinol = 6 μg β-carotene = 12 μg of other provitamin A carotenoids.
Interactions
Médicaments
Retinoids: strong interaction
Retinoids are derivatives of vitamin A, so concurrent use may have additive toxic effects.
Tetracyclines: moderate interaction
Concurrent use of vitamin A and tetracycline antibiotics increases the risk of intracranial hypertension.
Warfarin: moderate interaction
Taking high doses of vitamin A in combination with warfarin may increase the risk of bleeding.
Plantes ou autres actifs
Vitamin A: moderate interaction
Some studies suggest that vitamin E may reduce the absorption of beta-carotene. Taking 800 units of vitamin E per day appears to reduce plasma beta-carotene levels by 20%. Higher doses are thought to further reduce beta-carotene levels.
