Discussions on "Vitamin A" in "Healthy and Nutritive Foods" forum.
30th Aug 2011, 08:35 AM #1
Vitamin A (or Vitamin A Retinol, retinal, and four carotenoids including beta carotene) is a vitamin that is needed by the retina of the eye in the form of a specific metabolite, the light-absorbing molecule retinal, that is necessary for both low-light (scotopic vision) and color vision. Vitamin A also functions in a very different role, as an irreversibly oxidized form of retinol known as retinoic acid, 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 the 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. The associated acid (retinoic acid), a metabolite that can be irreversibly synthesized from vitamin A, has only partial vitamin A activity, and does not function in the retina for the visual cycle.
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 is found naturally in many foods:
carrots,liver (beef, pork, chicken, turkey, fish) (6500 μg 722%), including cod liver oil
Vitamin A functions:
Embryonic development and reproduction
Skin and cellular health
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30th Aug 2011, 03:06 PM #2Newbie
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- Aug 2011
Re: Vitamin A
Informative read about vitamin A,It is a fat-soluble vitamin that is essential to maintaining good overall health. A deficiency of vitamin A can lead to a number of health problems, ranging from mild to severe ailments.
14th Sep 2011, 05:06 PM #3Newbie
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- Sep 2011
Re: Vitamin A
Vitamin A is an important element and good for many reasons. It makes bones and muscles strong. It is good for eye sight. It makes hair strong. Any deficiency of vitamin A can causes many problems.
Last edited by sumathisrini; 30th Nov 2012 at 04:11 PM.