Retinol

vitamin Aretinol metabolismAretinol-binding proteinsA 1 REretinoic acidretinylVitamin A (Retinol)Vitamin A deficiency
Retinol, also known as Vitamin A 1, is a vitamin found in food and used as a dietary supplement.wikipedia
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Vitamin

vitaminsfat-soluble vitaminsfat-soluble vitamin
Retinol, also known as Vitamin A 1, is a vitamin found in food and used as a dietary supplement.
The thirteen vitamins required by human metabolism are: vitamin A (retinols and carotenoids), vitamin B 1 (thiamine), vitamin B 2 (riboflavin), vitamin B 3 (niacin), vitamin B 5 (pantothenic acid), vitamin B 6 (pyridoxine), vitamin B 7 (biotin), vitamin B 9 (folic acid or folate), vitamin B 12 (cobalamins), vitamin C (ascorbic acid), vitamin D (calciferols), vitamin E (tocopherols and tocotrienols), and vitamin K (quinones).

Vitamin A deficiency

shortage of dietary vitamin AAvitamin A
As a supplement it is used to treat and prevent vitamin A deficiency, especially that which results in xerophthalmia.
The three forms of vitamin A include retinols, beta-carotenes, and carotenoids.

Retinoic acid

9-''cis''-retinoic acidRAretinoic acid gradient
It is converted in the body to retinal and retinoic acid through which it acts.
Retinoic acid is a metabolite of vitamin A (retinol) that mediates the functions of vitamin A required for growth and development.

Retinal

retinaldehydeall-trans-retinalretinylidene
It is converted in the body to retinal and retinoic acid through which it acts.
The other main forms of vitamin A, retinol, and a partially active form, retinoic acid, may both be produced from retinal.

Carotene

β-carotenecarotenesbeta carotene
The body converts the dimerized form, carotene, into vitamin A as it is needed, therefore high levels of carotene are not toxic compared to the ester (animal) forms.
β-Carotene is composed of two retinyl groups, and is broken down in the mucosa of the human small intestine by β-carotene 15,15'-monooxygenase to retinal, a form of vitamin A.

RPE65

Vitamin A is converted by the protein RPE65 within the retinal pigment epithelium into 11-cis-retinal.
RPE65 is expressed in the retinal pigment epithelium (RPE, a layer of epithelial cells that nourish the photoreceptor cells) and is responsible for the conversion of all-trans-retinyl esters to 11-cis-retinol during phototransduction.

Hypervitaminosis A

vitamin A toxicityHypervitaminosis A syndromeorange-yellow discoloration of the skin
High doses may result in an enlarged liver, dry skin, or hypervitaminosis A.
Hypervitaminosis A can be prevented by not ingesting more than the US Institute of Medicine Daily Tolerable Upper Level of intake for Vitamin A. This level is for synthetic and natural retinol ester forms of vitamin A. Carotene forms from dietary sources are not toxic.

Carotenoid

carotenoidscarotinoidketo-carotenoid
Precursors, also known as provitamins, which must be converted to active forms by the body, are obtained from fruits and vegetables containing yellow, orange and dark green pigments, known as carotenoids, the most well-known being β-carotene.
Carotenoids that contain unsubstituted beta-ionone rings (including beta-carotene, alpha-carotene, beta-cryptoxanthin and gamma-carotene) have vitamin A activity (meaning that they can be converted to retinol), and these and other carotenoids can also act as antioxidants.

Xerophthalmia

dry eyesxerophthalmic
As a supplement it is used to treat and prevent vitamin A deficiency, especially that which results in xerophthalmia.
Since retinoic acid cannot be reduced to retinal or retinol, these effects on the cornea must be specific to retinoic acid.

Nyctalopia

night blindnesscongenital stationary night blindnessnight-blindness
Night blindness is one of the first signs of vitamin A deficiency.
Another cause of night blindness is a deficiency of retinol, or vitamin A, found in fish oils, liver and dairy products.

Vitamin A

Avitamins ARAE
Retinol is in the vitamin A family.
Vitamin A is a group of unsaturated nutritional organic compounds that includes retinol, retinal, retinoic acid, and several provitamin A carotenoids (most notably beta-carotene).

International unit

IUinternational unitsInternational Units (IU)
When referring to dietary allowances or nutritional science, retinol is usually measured in international units (IU).
Many biological agents exist in different forms or preparations (e.g. vitamin A in the form of retinol or beta-carotene).

WHO Model List of Essential Medicines

World Health Organization's List of Essential MedicinesList of Essential MedicinesModel List of Essential Medicines
It is on the World Health Organization's List of Essential Medicines, the most effective and safe medicines needed in a health system.
Retinol

Liver (food)

liverbeef liverlivers
Liver (beef, pork, chicken, turkey, fish)
Animal livers are rich in iron, copper, the B vitamins and preformed vitamin A.

Retinol-binding protein

retinol binding protein
Retinol then attaches to a serum carrier, retinol binding protein, for transport to target tissues.
They are carrier proteins that bind retinol.

Vitamin E

EVitamins EE vitamins
In the intestine, vitamin A is protected from being chemically changed by vitamin E.
The oxidized α-tocopheroxyl radicals produced in this process may be recycled back to the active reduced form through reduction by other antioxidants, such as ascorbate, retinol or ubiquinol.

Retinol dehydrogenase

Retinal is then reduced to retinol by the enzyme retinol dehydrogenase.
Thus, the two substrates of this enzyme are retinol and NAD +, whereas its 3 products are retinal, NADH (or NADPH in the case where NADP + is a cofactor), and H +.

Cod liver oil

cod-liver oilfish-liver oilcod liver
Cod liver oil
Though similar in fatty acid composition to other fish oils, cod liver oil has higher concentrations of vitamins A and D. According to the United States Department of Agriculture, a tablespoon (13.6 grams or 14.8 mL) of cod liver oil contains 4,080 μg of retinol (vitamin A) and 34 μg of vitamin D. The Dietary Reference Intake of vitamin A is 900 μg per day for adult men and 700 μg per day for women, while that for vitamin D is 15 μg per day.

Golden rice

vitamin A
The golden rice project is one such effort, and is already undergoing trials.
Golden rice is a variety of rice (Oryza sativa) produced through genetic engineering to biosynthesize beta-carotene, a precursor of vitamin A, in the edible parts of rice.

Retinyl palmitate

vitamin A palmitate
Retinyl palmitate ("vitamin A palmitate") When prepared as a dietary supplement, retinol is stabilized as the ester derivatives retinyl acetate or retinyl palmitate.
Retinyl palmitate, or vitamin A palmitate, is the ester of retinol (vitamin A) and palmitic acid, with formula C 36 H 60 O 2.

Liver

hepaticliver protein synthesislivers
During the absorption process in the intestines, retinol is incorporated into chylomicrons as the ester form, and it is these particles that mediate transport to the liver.
Animal livers are rich in iron, vitamin A and vitamin B 12 ; and cod liver oil is commonly used as a dietary supplement.

Acne

acne vulgariscystic acneblemishes
Retinoic acid, termed Tretinoin in clinical usage, is used in the treatment of acne and keratosis pilaris in a topical cream.
Frequently used topical retinoids include adapalene, isotretinoin, retinol, tazarotene, and tretinoin.

Beta-Carotene

β-carotenebeta caroteneprovitamin A
Retinol is synthesized from the breakdown of β-carotene.
Within the intestinal wall (mucosa), β-carotene is partially converted into vitamin A (retinol) by an enzyme, dioxygenase.

Retinyl acetate

When prepared as a dietary supplement, retinol is stabilized as the ester derivatives retinyl acetate or retinyl palmitate.
Retinyl acetate (retinol acetate, vitamin A acetate) is a natural form of vitamin A which is the acetate ester of retinol.

Dietary supplement

dietary supplementsnutritional supplementnutritional supplements
Retinol, also known as Vitamin A 1, is a vitamin found in food and used as a dietary supplement.