Information about Vitamin A
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The structure of retinol, the most common dietary form of vitamin A
Vitamin A is an essential human nutrient. It exists not as a single compound, but in several forms. In foods of animal origin, the major form of vitamin A is an alcohol (retinol), but can also exist as an aldehyde (retinal), or as an acid (retinoic acid). Precursors to the vitamin (a provitamin) are present in foods of plant origin as some of the members of the carotenoid family of compounds.[1]
All forms of Vitamin A have a Beta-ionone ring to which an isoprenoid chain is attached. This structure is essential for vitamin activity.[1]
- retinol, the animal form of Vitamin A, is a yellow, fat-soluble, vitamin with importance in vision and bone growth.
- other retinoids, a class of chemical compounds that are related chemically to Vitamin A, are used in medicine.[2]
Discovery of Vitamin A
The discovery of Vitamin A stemmed from research dating back to 1906, indicating that factors other than carbohydrates, proteins, and fats were necessary to keep cattle healthy.[3] By 1917 one of these substances was independently discovered by Elmer McCollum at the University of Wisconsin-Madison, and Lafayette Mendel and Thomas Osborne at Yale University. Since "water-soluble factor B" (Vitamin B) had recently been discovered, the researchers chose the name "fat-soluble factor A".<ref name="Discovery" />Sources
Vitamin A is found naturally in many foods. Each of the following contains at least 0.15 mg of Vitamin A or beta carotene per 1.75-7 oz. (50-200 g): butter, lemon, sweet potatoes, carrots, collard greens, milk, beetroot, pumpkin, spinach, beef, apple, winter squash, apricots, cantaloupe melon, mango, liver, (beef, pork, chicken, turkey, fish) eggs, broccoli, and leafy vegetables.Recommended daily intake
Vitamin A US Dietary Reference Intake:- 900 micrograms for men
- 700 for women.
- Upper limit - 3,000 micrograms.
Equivalencies of retinoids and carotenoids
Vitamin A intake is often expressed in international units (IU) or as retinol equivalents (RE), with 1 IU = 0.3 micrograms retinol. Because the production of retinol from provitamins by the human body is regulated by the amount of retinol available to the body, the conversions apply strictly only for Vitamin A deficient humans. The absorption of provitamins also depends greatly on the amount of lipids ingested with the provitamin; lipids increase the uptake of the provitamin.[5]| Substance and its chemical environment | Micrograms of retinol equivalent per microgram of the substance |
|---|---|
| retinol | 1 |
| beta-carotene, dissolved in oil | 1/2 |
| beta-carotene, common dietary | 1/12 |
| alpha-carotene, common dietary | 1/24 |
| beta-cryptoxanthin, common dietary | 1/24 |
Conversion of carotenoids into retinol relies on adequate intake of vitamin C, zinc and protein.
Symptoms of deficiency
Night blindness, corneal drying (xerosis), triangular gray spots on eye (Bitot's spots), corneal degeneration and blindness (xerophthalmia)[6], impaired immunity, hypokeratosis (white lumps at hair follicles), softening of the cornea (keratomalacia).Symptoms of overdose
As vitamin A is fat-soluble, disposing of any excesses taken in through diet is a lot harder than with water-soluble vitamins B and C. As such, vitamin A toxicity can result. This can lead to nausea, jaundice, irritability, anorexia (not to be confused with anorexia nervosa, the eating disorder), vomiting, blurry vision, headaches, muscle and abdominal pain and weakness, drowsiness and altered mentality.
In chronic cases, hair loss, drying of the mucous membranes, fever, insomnia, fatigue, weight loss, bone fractures, anemia, and diarrhea can all be evident on top of the symptoms associated with less serious toxicity.[7]
See also
External links
References
1. ^ Carolyn Berdanier. 1997. Advanced Nutrition Micronutrients. pp 22-39
2. ^ American Cancer Society: Retinoid Therapy
3. ^ Wolf, George (2001-04-19). "Discovery of Vitamin A". Encyclopedia of Life Sciences. doi:10.1038/npg.els.0003419. Retrieved on 2007-07-21.
4. ^ Sources of vitamin A. Retrieved on 2007-08-27.
5. ^ NW Solomons, M Orozco. Alleviation of Vitamin A deficiency with palm fruit and its products. Asia Pac J Clin Nutr, 2003
6. ^ Roncone DP (2006). "Xerophthalmia secondary to alcohol-induced malnutrition". Optometry (St. Louis, Mo.) 77 (3): 124-33. DOI:10.1016/j.optm.2006.01.005. PMID 16513513. Retrieved on 2007-08-18.
7. ^ [1]
2. ^ American Cancer Society: Retinoid Therapy
3. ^ Wolf, George (2001-04-19). "Discovery of Vitamin A". Encyclopedia of Life Sciences. doi:10.1038/npg.els.0003419. Retrieved on 2007-07-21.
4. ^ Sources of vitamin A. Retrieved on 2007-08-27.
5. ^ NW Solomons, M Orozco. Alleviation of Vitamin A deficiency with palm fruit and its products. Asia Pac J Clin Nutr, 2003
6. ^ Roncone DP (2006). "Xerophthalmia secondary to alcohol-induced malnutrition". Optometry (St. Louis, Mo.) 77 (3): 124-33. DOI:10.1016/j.optm.2006.01.005. PMID 16513513. Retrieved on 2007-08-18.
7. ^ [1]
Carotenoid: retinoids |
|---|
| Acitretin - Alitretinoin - Bexarotene - Etretinate - Fenretinide - Isotretinoin - Retinaldehyde - Tazarotene - Vitamin A (Retinol, Tretinoin) |
Vitamins (A11) | |
|---|---|
| fat soluble | Retinol (A) | Ergocalciferol and Cholecalciferol (D) | Tocopherol (E) | Naphthoquinone (K) |
| water soluble | B vitamins (Thiamine (B1), Riboflavin (B2), Niacin (B3), Pantothenic acid (B5), Pyridoxine (B6), Biotin (B7), Folic acid (B9), Cyanocobalamin (B12)) | Choline | Ascorbic acid (C) |
alcohol is any organic compound in which a hydroxyl group (-OH) is bound to a carbon atom of an alkyl or substituted alkyl group. The general formula for a simple acyclic alcohol is CnH2n+1OH.
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Retinol (Afaxin), the animal form of vitamin A, is a fat-soluble vitamin important in vision and bone growth. It belongs to the family of chemical compounds known as retinoids.
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aldehyde is an organic compound containing a terminal carbonyl group. This functional group, which consists of a carbon atom which is bonded to a hydrogen atom and double-bonded to an oxygen atom (chemical formula O=CH-), is called the aldehyde group.
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Retinal, technically called retinene1 or "retinaldehyde", is a light-sensitive retinene molecule found in the photoreceptor cells of the retina. Retinal is the fundamental chromophore involved in the transduction of light into visual signals, i.e.
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Retinoic acid is the acidified form of Vitamin A.
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- For its endogenous natural role, see Retinol
- For its use in clinical treatment of various conditions, see Tretinoin
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A provitamin is a substance that can be converted into a vitamin by animal tissues. For example, carotene can be converted to Vitamin A by the human body.
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Carotenoids are organic pigments that are naturally occurring in plants and some other photosynthetic organisms like algae, some types of fungus and some bacteria. There are over 600 known carotenoids; they are split into two classes, xanthophylls and carotenes.
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Ionone or 4-(2,6,6-trimethyl-1-cyclohexen-1-yl)-3-buten-2-one or cyclocitrylideneacetone or irisone C13H20O is a chemical substance and part of the terpene family. Ionone is an aroma compound.
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Isoprene is a common synonym for the chemical compound 2-methylbuta-1,3-diene. It is commonly used in industry, is an important biological material, and can be a harmful environmental pollutant and toxicant when present in excess quantities.
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Retinol (Afaxin), the animal form of vitamin A, is a fat-soluble vitamin important in vision and bone growth. It belongs to the family of chemical compounds known as retinoids.
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A vitamin is a nutrient that is an organic compound required in tiny amounts for essential metabolic reactions in a living organism.[1] The term vitamin
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The retinoids are a class of chemical compounds that are related chemically to vitamin A. Retinoids are used in medicine, primarily due to the way they regulate epithelial cell growth.
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19th century - 20th century - 21st century
1870s 1880s 1890s - 1900s - 1910s 1920s 1930s
1903 1904 1905 - 1906 - 1907 1908 1909
Year 1906 (MCMVI
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1870s 1880s 1890s - 1900s - 1910s 1920s 1930s
1903 1904 1905 - 1906 - 1907 1908 1909
Year 1906 (MCMVI
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Proteins are large organic compounds made of amino acids arranged in a linear chain and joined together by peptide bonds between the carboxyl and amino groups of adjacent amino acid residues.
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Fat
Fat may refer to:- Fat, a group of compounds that are generally soluble in organic solvents and largely insoluble in water
- Adipose tissue, an anatomical term for loose connective tissue composed of adipocytes
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19th century - 20th century - 21st century
1880s 1890s 1900s - 1910s - 1920s 1930s 1940s
1914 1915 1916 - 1917 - 1918 1919 1920
Year 1917 (MCMXVII
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1880s 1890s 1900s - 1910s - 1920s 1930s 1940s
1914 1915 1916 - 1917 - 1918 1919 1920
Year 1917 (MCMXVII
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Associated with the discovery of Vitamin A, Elmer McCollum was a biochemist at the University of Wisconsin, who in 1913, along with colleague Marguerite Davis identified a fat-soluble nutrient in butterfat and cod liver oil.
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University of Wisconsin–Madison (also known as UW–Madison, Madison, Wisconsin, University of Wisconsin, or UW) is a highly selective public research university located in Madison, Wisconsin, USA.
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Lafayette Mendel
Born January 5 1872
Delhi, New York, U.S.
Died November 9 1935 (aged 63)
New Haven, Connecticut, U.S.
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Born January 5 1872
Delhi, New York, U.S.
Died November 9 1935 (aged 63)
New Haven, Connecticut, U.S.
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Yale University is a private university in New Haven, Connecticut. Founded in 1701 as the Collegiate School, Yale is the third-oldest institution of higher education in the United States and is a member of the Ivy League.
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The B vitamins are eight water-soluble vitamins that play important roles in cell metabolism. Historically, the B vitamins were once thought to be a single vitamin, referred to as Vitamin B (much like how people refer to Vitamin C or Vitamin D).
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Butter is a dairy product, made by churning fresh or fermented cream or milk. Butter is used as a spread and a condiment, as well as in cooking applications such as baking, sauce making, and frying.
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C. × limon
Binomial name
Citrus × limon
(L.) Burm.f.
The lemon (Citrus × limon) is a hybrid in cultivated wild plants.
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Binomial name
Citrus × limon
(L.) Burm.f.
The lemon (Citrus × limon) is a hybrid in cultivated wild plants.
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I. batatas
Binomial name
Ipomoea batatas
L.
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Binomial name
Ipomoea batatas
L.
“Camote” redirects here. For the island group in the Philippines, see Camotes Islands.
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D. carota
Binomial name
Daucus carota
L.
The carrot (Daucus carota subsp. sativus
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Binomial name
Daucus carota
L.
The carrot (Daucus carota subsp. sativus
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Collards, also called collard greens or borekale (Brassica oleracea Acephala Group), are various loose-leafed cultivars of the cabbage plant. The plant is grown for its large, dark-colored, edible leaves and as a garden ornamental, mainly in Brazil, Portugal,
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Milk is an opaque white liquid produced by the mammary glands of female mammals (including monotremes). Mammary glands are highly specialized sweat glands. The female ability to produce milk is one of the defining characteristics of mammals.
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B. vulgaris
Binomial name
Beta vulgaris
Carolus Linnaeus
Beta vulgaris, commonly known as beet or beetroot, is a flowering plant species in the family Chenopodiaceae.
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Binomial name
Beta vulgaris
Carolus Linnaeus
Beta vulgaris, commonly known as beet or beetroot, is a flowering plant species in the family Chenopodiaceae.
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