Vitamin A: Benefits, Dosage, Contraindications
Other name(s)
Beta-Carotene, Retinol
Family or group:
Vitamins
Indications
Rating methodology
EFSA approval.
Vitamin A Deficiency ✪✪✪✪✪
While most vitamin A deficiencies are not severe enough to be associated with defined and observable symptoms, stress sources, such as measles, pneumonia, or diarrhea, can reduce its levels further and lead to serious illness. Deficiency of vitamin A can impair vision, ranging from decreased night vision to blindness. Nutritional Reference Values (NRVs) are suggested to cover the "normal" nutritional needs for a population. NRVs for vitamin A in adults were updated in 2016. They are 750 µg of RE per day for men (vitamin A activity is expressed relative to that of retinol according to a retinol equivalent system (RE)) and 650 µg for women.
Posologie
Orally
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 Carotenoids Presentation, Food Sources, and Nutritional Needs
Skin Health ✪✪✪✪✪
Vitamin A is necessary for the integrity of mucosal and epithelial surfaces. A deficiency in vitamin A causes keratinization of epithelial surfaces, leading to skin dryness.
Posologie
Orally
750 - 3000 µg
Adults
Eye Health ✪✪✪✪✪
Vitamin A contributes to normal vision. It is necessary for maintaining the conjunctival and corneal epithelium. It is also necessary for epithelial RNA synthesis. Vitamin A deficiency is a leading cause of blindness in developing countries. When its intake is insufficient, night vision becomes difficult, the cornea thickens, and eventually dies.
Posologie
Orally
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 neuronal development and is also involved in the development of limbs, lungs, heart, eyes, and ears. However, an excess of vitamin A is teratogenic, causing malformations of the central nervous system, craniofacial, cardiovascular, and thymus defects.
Posologie
Oral administration
700 - 3000 bcg
Pregnant women
Wrinkles ✪✪✪✪✪
The topical application of a vitamin A-based night cream seems to reliably reduce the appearance of fine lines. To obtain beneficial effects on the skin, the retinol concentration in the cream must be significant (at least 0.3%). Treatment begins with two applications per week, up to one daily application.
Posologie
Topical application
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 the progression of the disease.
Posologie
Oral administration
15 mg
10 - years
Adults
Long-term effects of vitamins C and E, b2-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 in the form of retinyl palmitate for 6 months, followed by 10,000 IU per day for 6 months, may relieve symptoms in affected patients.
Posologie
Oral administration
10000 - 25000 IU
12 - months
Adults
Breast Cancer ✪✪✪✪✪
Epidemiological data shows a link between high dietary intake of vitamin A and a reduced risk of breast cancer in premenopausal women with a family history of breast cancer. However, it is unknown if vitamin A supplements offer the same benefits. A daily dose of 700 mcg (equivalent to 2300 IU) is recommended to prevent potential breast cancer.
Posologie
Oral administration
2300 - 2300 IU
Women
Rheumatoid Arthritis ✪✪✪✪✪
Preliminary clinical research has shown that taking a supplement containing astaxanthin (4 mg), lutein (40 bcg), vitamin A (65 IU), vitamin E (50 IU), and safflower oil (460 mg), three times a day for 8 weeks, reduces pain and increases satisfaction by about 40% compared to placebo in patients with rheumatoid arthritis.
Posologie
Oral administration
195 IU
8 - weeks
Adults
Synergies
Properties
Essential
Vitamin A is important for the health of mucous membranes, skin, and eyes. It is generally sufficient in the body. A deficiency may 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 elderly), the consequences of moderate vitamin A deficiencies, particularly in relation to infectious states, could be concerning. Decreased visual acuity, especially in low light (night vision), is one of the first apparent signs of vitamin A deficiency in humans.
Usages associés
Dermatological Effect
A carboxylic acid ester of retinol known as all-trans retinoic acid (ATRA), also known by various names such as tretinoin, is the most used form of vitamin A. In cultures, ATRA has been found to increase collagen synthesis (anabolism) and inhibit enzymes responsible for collagen breakdown, such as collagenase and gelatinase. Moreover, ATRA reduces collagen degradation caused by ultraviolet radiation.
Usages associés
Vision
Vitamin A is necessary for maintaining the conjunctival and corneal epithelium. It is also needed for epithelial RNA synthesis. In the retina, rhodopsin or retinal purple (a photosensitive protein pigment present in the photoreceptor cells of the retina which are the rods) is necessary for the transduction of light into neuronal signals producing vision. It is comprised of a transmembrane protein, opsin, to which retinal, an aldehyde form of vitamin A or beta-carotene, binds. The most specific indicator of vitamin A deficiency is xerophthalmia, initially manifested by night blindness that progresses to total vision loss if untreated.
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 may increase cytokine production, such as interleukin 1 (IL-1). Moreover, the growth, differentiation, and activation of B lymphocytes depend on retinol. On the other hand, retinoic acid can suppress the proliferation of pathogenic T lymphocytes present in multiple sclerosis and increase the production of regulatory cells modulating the immune system.
Usages associés
Anti-Inflammatory
Retinoic acid has been shown to stimulate anti-inflammatory effects, reduce the production of inflammatory cytokines, and modify the levels of retinoic acid receptors present on immune cells secreting anti-inflammatory cytokines.
Usages associés
Anticancer
Retinoids may help to prevent cancer by inducing tumor suppressor genes called retinoic acid receptors (RAR) which are absent in many malignant tumor cells, likely due to gene methylation. Once demethylated, they 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. As such, it reduces oxidative stress and stimulates immune function in cases of cancer.
Usages associés
Antioxidant
Vitamin A exhibits free radical scavenging properties and is generally considered an antioxidant molecule. Vitamin A linked to protein kinase C is an essential cofactor in the redox activation of the mitochondrial signaling pathway. Furthermore, 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 rat brains.
Safety dosage
Adult from 18 years: 800 bcg - 3000 bcg
Values relate 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 was introduced and defined as 1 bcg RE = 1 bcg retinol = 6 bcg b2-carotene = 12 bcg other carotenoids with provitamin A activity.
Infant up to 12 months: 250 bcg
Values relate 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 was introduced and defined as 1 bcg RE = 1 bcg retinol = 6 bcg b2-carotene = 12 bcg other carotenoids with provitamin A activity.
Child from 1 to 3 years: 250 bcg - 800 bcg
Values relate 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 was introduced and defined as 1 bcg RE = 1 bcg retinol = 6 bcg b2-carotene = 12 bcg other carotenoids with provitamin A activity.
Child from 4 to 6 years: 300 bcg - 1100 bcg
Values relate 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 was introduced and defined as 1 bcg RE = 1 bcg retinol = 6 bcg b2-carotene = 12 bcg other carotenoids with provitamin A activity.
Child from 7 to 10 years: 400 bcg - 1500 bcg
Values relate 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 was introduced and defined as 1 bcg RE = 1 bcg retinol = 6 bcg b2-carotene = 12 bcg other carotenoids with provitamin A activity.
Child from 15 to 17 years: 750 bcg - 2600 bcg
Values relate 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 was introduced and defined as 1 bcg RE = 1 bcg retinol = 6 bcg b2-carotene = 12 bcg other carotenoids with provitamin A activity.
Child from 11 to 14 years: 600 bcg - 2000 bcg
Values relate 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 was introduced and defined as 1 bcg RE = 1 bcg retinol = 6 bcg b2-carotene = 12 bcg other carotenoids with provitamin A activity.
Menopause from 50 years: 650 bcg
Values relate 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 was introduced and defined as 1 bcg RE = 1 bcg retinol = 6 bcg b2-carotene = 12 bcg other carotenoids with provitamin A activity.
Pregnant woman from 18 years: 700 bcg - 3000 bcg
Values relate 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 was introduced and defined as 1 bcg RE = 1 bcg retinol = 6 bcg b2-carotene = 12 bcg other carotenoids with provitamin A activity.
Breastfeeding woman from 18 years old: 1300 µg - 3000 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 compared to retinol. To account for these differences, REs have been introduced and defined as 1 µg RE = 1 µg retinol = 6 µg β-carotene = 12 µg of other provitamin A active carotenoids.
Interactions
Médicaments
Retinoids: strong interaction
Retinoids are derivatives of vitamin A, so their concomitant intake can have additive toxic effects.
Tetracyclines: moderate interaction
Concomitant intake of vitamin A and tetracycline antibiotics increases the risk of intracranial hypertension.
Warfarin: moderate interaction
Taking high doses of vitamin A in conjunction 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.
