What are the properties of Vitamin A in supplements?

The properties of Vitamin A

Vitamin A is a micronutrient that is crucial for maintaining vision, promoting growth and development, and protecting epithelium and mucus integrity in the body. Vitamin A is known as an anti-inflammation vitamin because of its critical role in enhancing immune function. Vitamin A is involved in the development of the immune system and plays regulatory roles in cellular immune responses and humoral immune processes. Vitamin A has demonstrated a therapeutic effect in the treatment of various infectious diseases.

Vitamin A, and more specifically, retinoic acid, maintain normal skin health by switching on genes and differentiating keratinocytes (immature skin cells) into mature epidermal cells. For the treatment of acne, the most prescribed retinoid drug is 13-cis retinoic acid (isotretinoin). It reduces the size and secretion of the sebaceous glands.

Vitamin A exists in the diet as preformed vitamin A (from animal sources) and as provitamin A carotenoids (sourced from plants). Both sources of vitamin A must be metabolized intracellularly to their active forms (retinal and retinoic acid).

Retinol, Beta-Carotene, Vitamin A Palmitate and Retinyl Acetate - Description from NCI Thesaurus

Retinol

Definition: The fat soluble vitamin retinol. Vitamin A binds to and activates retinoid receptors (RARs), thereby inducing cell differentiation and apoptosis of some cancer cell types and inhibiting carcinogenesis. Vitamin A plays an essential role in many physiologic processes, including proper functioning of the retina, growth and differentiation of target tissues, proper functioning of the reproductive organs, and modulation of immune function.

CRCH Definition: Retinoid with a hydroxyl group. Active form of vitamin A which can be converted to the other usable forms; retinal (an aldehyde) and retinoic acid (a carboxylic acid). Read more about Retinol on NCI Thesaurus: C68302.

Beta-Carotene

Definition: A naturally-occurring retinol (vitamin A) precursor obtained from certain fruits and vegetables with potential antineoplastic and chemopreventive activities. As an anti-oxidant, beta carotene inhibits free-radical damage to DNA. This agent also induces cell differentiation and apoptosis of some tumor cell types, particularly in early stages of tumorigenesis, and enhances immune system activity by stimulating the release of natural killer cells, lymphocytes, and monocytes. (NCI04)

NCI-GLOSS Definition: A substance found in yellow and orange fruits and vegetables and in dark green, leafy vegetables. The body can make vitamin A from beta carotene. Beta carotene is being studied in the prevention of some types of cancer. It is a type of antioxidant.

CRCH Definition: Carotenoid consisting of a cyclic structure on each end with additional double bonds at the number 5 and 5' carbon atoms of the cyclic structures. Read more about NCI Thesaurus on NCI Thesaurus: C1016

Vitamin A Palmitate

Definition: A naturally-occurring phenyl analogue of retinol (vitamin A) with potential antineoplastic and chemopreventive activities. As the most common form of vitamin A taken for dietary supplementation, retinyl palmitate binds to and activates retinoid receptors, thereby inducing cell differentiation and decreasing cell proliferation. This agent also inhibits carcinogen-induced neoplastic transformation, induces apoptosis in some cancer cell types, and exhibits immunomodulatory properties. (NCI04)

NCI-GLOSS Definition: A drug being studied in cancer prevention. It belongs to the family of drugs called retinoids. Read more about NCI Thesaurus on NCI Thesaurus: C1217

Retinyl Acetate

Definition: A naturally-occurring fatty acid ester form of retinol (vitamin A) with potential antineoplastic and chemopreventive activities. Retinyl acetate binds to and activates retinoid receptors, inducing cell differentiation and decreasing cell proliferation. This agent also inhibits carcinogen-induced neoplastic transformation in some cancer cell types and exhibits immunomodulatory properties. (NCI04) Read more about NCI Thesaurus on NCI Thesaurus: C1216

Retinol and Beta-Carotene - Description from ChemIDplus

Retinol and Beta-Carotene - Description from DrugBank

Retinol, Beta-Carotene and Vitamin A Palmitate - Description from Wikipedia

Retinol

The Dietary Reference Intake (DRI) Recommended Daily Amount (RDA) for vitamin A for a 25-year-old male is 900 micrograms/day, or 3000 IU. NHS daily recommended values are slightly lower at 700 micrograms for men and 600 micrograms for women.

Estimates have changed over time of the rate at which β-carotene is converted to vitamin A in the human body. An early estimate of 6:1 was revised to 12:1 and from recent studies and experimental trials carried out in developing nations it was revised again to 21:1. The implication of the reduced estimate is that larger quantities of β-carotene are needed to yield the necessary dietary requirement of vitamin A. This means that more continents are affected by the deficiency of vitamin A than was previously thought. Changing dietary choices in Africa, Asia, and South America will not be sufficient, and agricultural practices on those continents will need to change.

The Food Standards Agency states that an average adult should not consume more than 1500 micrograms (5000 IU) per day, because this increases the chance of osteoporosis.

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. Liver cells (hepatocytes) store vitamin A as the ester, and when retinol is needed in other tissues, it is de-esterifed and released into the blood as the alcohol. Retinol then attaches to a serum carrier, retinol binding protein, for transport to target tissues. A binding protein inside cells, cellular retinoic acid binding protein, serves to store and move retinoic acid intracellularly. Carotenoid bioavailability is 1⁄10 to 1⁄5 that of retinol. Carotenoids are better absorbed when ingested as part of a fatty meal. Also, the carotenoids in vegetables, especially those with tough cell walls (e.g. carrots), are better absorbed when these cell walls are broken up by cooking or mincing. Read more about Retinol on Wikipedia: Retinol.

Beta-Carotene

Since 2001, the US Institute of Medicine uses retinol activity equivalents (RAE) for their Dietary Reference Intakes, defined as follows:

Retinol activity equivalents (RAEs)

1 µg RE = 1 µg retinol
1 µg RAE = 2 µg all-trans-β-carotene from supplements
1 µg RAE = 12 µg of all-trans-β-carotene from food
1 µg RAE = 24 µg α-carotene or β-cryptoxanthin from food

RAE takes into account carotenoids' variable absorption and conversion to vitamin A by humans better than and replaces the older retinol equivalent (RE) (1 µg RE = 1 µg retinol, 6 µg β-carotene, or 12 µg α-carotene or β-cryptoxanthin). RE was developed 1967 by the United Nations/World Health Organization Food and Agriculture Organization (FAO/WHO).

Another older unit of vitamin A activity is the international unit (IU). Like retinol equivalent, the international unit does not take into account carotenoids' variable absorption and conversion to vitamin A by humans, as well as the more modern retinol activity equivalent. Unfortunately, food and supplement labels still generally use IU, but IU can be converted to the more useful retinol activity equivalent as follows:

International Units

1 µg RAE = 3.33 IU retinol
1 IU retinol = 0.3 μg RAE
1 IU β-carotene from supplements = 0.15 μg RAE
1 IU β-carotene from food = 0.05 μg RAE
1 IU α-carotene or β-cryptoxanthin from food = 0.025 μg RAE1

Read more about Wikipedia on Wikipedia: Beta-Carotene

Vitamin A Palmitate

Retinyl acetate is a synthetic alternate for retinyl palmitate in vitamin A supplements, and is available in oily or dry forms. It is a common vitamin supplement, available in both oral and injectable forms for treatment of vitamin A deficiency, under the brand names Aquasol A, Palmitate A and many others. It is a constituent of intra ocular treatment for dry eyes at a concentration of 138 μg/g (VitA-Pos) by Ursapharm. It is a pre-formed version of vitamin A; therefore, the intake should not exceed the Recommended Dietary Allowance (RDA). Overdosing preformed Vitamin A forms such as retinyl palmitate leads to adverse physiological reactions (hypervitaminosis A).

Retinyl palmitate is used as an antioxidant and a source of vitamin A added to low fat milk and other dairy products to replace the vitamin content lost through the removal of milk fat. Palmitate is attached to the alcohol form of vitamin A, retinol, in order to make vitamin A stable in milk.

Retinyl palmitate is also a constituent of some topically applied skin care products. After its absorption into the skin, retinyl palmitate is converted to retinol, and ultimately to retinoic acid (the active form of vitamin A present in Retin-A), though neither its skin absorption nor its conversion is very effective. Read more about Wikipedia on Wikipedia: Retinyl_palmitate

The supplements containing Vitamin A

Acti vita-miner Senior, drażetki dla osób po 50 roku życia, 60 szt. / (Aflofarm)

Multivitamins Natural Nutrients Vitamins TBSS ID: SUCC0290
Acti vita-miner Senior, drażetki dla osób po 50 roku życia, 60 szt. / (Aflofarm) contains Vitamin A.

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What are the properties of Vitamin A in supplements?

The properties of Vitamin A

Retinol, Beta-Carotene, Vitamin A Palmitate and Retinyl Acetate - Description from NCI Thesaurus

Retinol

Beta-Carotene

Vitamin A Palmitate

Retinyl Acetate

Retinol and Beta-Carotene - Description from ChemIDplus

Retinol

Beta-Carotene

Retinol and Beta-Carotene - Description from DrugBank

Retinol

Beta-Carotene

Retinol, Beta-Carotene and Vitamin A Palmitate - Description from Wikipedia

Retinol

Beta-Carotene

Retinol activity equivalents (RAEs)

International Units

Vitamin A Palmitate

The supplements containing Vitamin A

Vitamin A (Retinol) - References & External links

Vitamin A (Retinol)

Related substances

Beta-Carotene

Beta-Carotene

Vitamin A Palmitate

Vitamin A Palmitate

Retinyl Acetate

Retinyl Acetate