Vitamin A
Common name
ID
HD0063
Scientific name of the plant
Anatomical part for use
Human use
Miscellaneous
Summary
Vitamin A is a group of unsaturated nutritional organic compounds that includes retinol, retinal, and several provitamin A carotenoids (most notably beta-carotene). Vitamin A has multiple functions: it is important for growth and development, for the maintenance of the immune system, and for good vision. Vitamin A is needed by the retina of the eye in the form of retinal, which combines with protein opsin to form rhodopsin, the light-absorbing molecule necessary for both low-light (scotopic vision) and color vision. Vitamin A also functions in a very different role as retinoic acid (an irreversibly oxidized form of retinol), which is an important hormone-like growth factor for epithelial and other cells.In foods of animal origin, the major form of vitamin A is an ester, primarily retinyl palmitate, which is converted to retinol (chemically an alcohol) in the small intestine. The retinol form functions as a storage form of the vitamin, and can be converted to and from its visually active aldehyde form, retinal.All forms of vitamin A have a beta-ionone ring to which an isoprenoid chain is attached, called a retinyl group. Both structural features are essential for vitamin activity. The orange pigment of carrots (beta-carotene) can be represented as two connected retinyl groups, which are used in the body to contribute to vitamin A levels. Alpha-carotene and gamma-carotene also have a single retinyl group, which give them some vitamin activity. None of the other carotenes have vitamin activity. The carotenoid beta-cryptoxanthin possesses an ionone group and has vitamin activity in humans.
Vitamin A can be found in two principal forms in foods:
Retinol, the form of vitamin A absorbed when eating animal food sources, is a yellow, fat-soluble substance. Since the pure alcohol form is unstable, the vitamin is found in tissues in a form of retinyl ester. It is also commercially produced and administered as esters such as retinyl acetate or palmitate.
The carotenes alpha-carotene, beta-carotene, gamma-carotene; and the xanthophyll beta-cryptoxanthin (all of which contain beta-ionone rings), but no other carotenoids, function as provitamin A in herbivores and omnivore animals, which possess the enzyme beta-carotene 15,15'-dioxygenase in the intestinal mucosa to cleave and convert provitamin A to retinol.
Evidence Level
Level 4 (Individual reports repeated observed over 5 years among different countries)
Hepatotoxicity reports in literature
- The vitamin A spectrum: from deficiency to toxicity : (Source)
- Hepatic hydrothorax associated with vitamin a toxicity : (Source)
- Reversible hepatic injury induced by long-term vitamin A ingestion : (Source)
- Liver fibrosis in a patient with familial homozygous hypobetalipoproteinaemia: possible role of vitamin supplementation : (Source)
- Vitamin A toxicity in a physical culturist patient: a case report and review of the literature : (Source)
- Hypervitaminosis A inducing intra-hepatic cholestasis--a rare case report : (Source)
- Excess vitamin A injures the liver : (Source)
- Hepatic and dermatologic manifestations of chronic hypervitaminosis A in adults. Report of two cases : (Source)
- Vitamin A hepatotoxicity in multiple family members : (Source)
- The histopathologic progression of vitamin A-induced hepatic injury : (Source)
- Hepatic injury from chronic hypervitaminosis a resulting in portal hypertension and ascites : (Source)
- #N/A : (Source)
- Peliosis-like ultrastructural changes of the hepatic sinusoids in human chronic hypervitaminosis A: report of three cases : (Source)
- Liver damage with reversible portal hypertension from vitamin A intoxication: demonstration of Ito cells : (Source)
- Reversible hepatotoxicity associated with hepatic vitamin A accumulation in a protein-deficient patient : (Source)
- Hypervitaminosis A unmasked by acute viral hepatitis : (Source)
- Vitamin A hepatotoxicity: a cautionary note regarding 25,000 IU supplements : (Source)
Hepatotoxicity Description
N/A
Common name
ID
HD0063
Scientific name of the plant
Anatomical part for use
Human use
Miscellaneous
Summary
Vitamin A is a group of unsaturated nutritional organic compounds that includes retinol, retinal, and several provitamin A carotenoids (most notably beta-carotene). Vitamin A has multiple functions: it is important for growth and development, for the maintenance of the immune system, and for good vision. Vitamin A is needed by the retina of the eye in the form of retinal, which combines with protein opsin to form rhodopsin, the light-absorbing molecule necessary for both low-light (scotopic vision) and color vision. Vitamin A also functions in a very different role as retinoic acid (an irreversibly oxidized form of retinol), which is an important hormone-like growth factor for epithelial and other cells.In foods of animal origin, the major form of vitamin A is an ester, primarily retinyl palmitate, which is converted to retinol (chemically an alcohol) in the small intestine. The retinol form functions as a storage form of the vitamin, and can be converted to and from its visually active aldehyde form, retinal.All forms of vitamin A have a beta-ionone ring to which an isoprenoid chain is attached, called a retinyl group. Both structural features are essential for vitamin activity. The orange pigment of carrots (beta-carotene) can be represented as two connected retinyl groups, which are used in the body to contribute to vitamin A levels. Alpha-carotene and gamma-carotene also have a single retinyl group, which give them some vitamin activity. None of the other carotenes have vitamin activity. The carotenoid beta-cryptoxanthin possesses an ionone group and has vitamin activity in humans. Vitamin A can be found in two principal forms in foods: Retinol, the form of vitamin A absorbed when eating animal food sources, is a yellow, fat-soluble substance. Since the pure alcohol form is unstable, the vitamin is found in tissues in a form of retinyl ester. It is also commercially produced and administered as esters such as retinyl acetate or palmitate. The carotenes alpha-carotene, beta-carotene, gamma-carotene; and the xanthophyll beta-cryptoxanthin (all of which contain beta-ionone rings), but no other carotenoids, function as provitamin A in herbivores and omnivore animals, which possess the enzyme beta-carotene 15,15'-dioxygenase in the intestinal mucosa to cleave and convert provitamin A to retinol.
Evidence Level
Level 4 (Individual reports repeated observed over 5 years among different countries)
Hepatotoxicity reports in literature
- The vitamin A spectrum: from deficiency to toxicity : (Source)
- Hepatic hydrothorax associated with vitamin a toxicity : (Source)
- Reversible hepatic injury induced by long-term vitamin A ingestion : (Source)
- Liver fibrosis in a patient with familial homozygous hypobetalipoproteinaemia: possible role of vitamin supplementation : (Source)
- Vitamin A toxicity in a physical culturist patient: a case report and review of the literature : (Source)
- Hypervitaminosis A inducing intra-hepatic cholestasis--a rare case report : (Source)
- Excess vitamin A injures the liver : (Source)
- Hepatic and dermatologic manifestations of chronic hypervitaminosis A in adults. Report of two cases : (Source)
- Vitamin A hepatotoxicity in multiple family members : (Source)
- The histopathologic progression of vitamin A-induced hepatic injury : (Source)
- Hepatic injury from chronic hypervitaminosis a resulting in portal hypertension and ascites : (Source)
- #N/A : (Source)
- Peliosis-like ultrastructural changes of the hepatic sinusoids in human chronic hypervitaminosis A: report of three cases : (Source)
- Liver damage with reversible portal hypertension from vitamin A intoxication: demonstration of Ito cells : (Source)
- Reversible hepatotoxicity associated with hepatic vitamin A accumulation in a protein-deficient patient : (Source)
- Hypervitaminosis A unmasked by acute viral hepatitis : (Source)
- Vitamin A hepatotoxicity: a cautionary note regarding 25,000 IU supplements : (Source)
Hepatotoxicity Description
N/A