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Vitamin A


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  1. #1
    surya's Avatar
    surya is offline Citizen's of Penmai
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    Vitamin A

    Vitamin A


    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
    carrot
    broccoli leaf
    sweet potato
    butter
    spinach
    pumpkin
    collard greens
    Cheddar cheese
    cantaloupe melon
    egg
    apricot
    papaya
    mango
    pea
    broccoli
    milk




    Vitamin A functions:


    Vision
    Gene transcription
    Immune function
    Embryonic development and reproduction
    Bone metabolism
    Haematopoiesis
    Skin and cellular health
    Antioxidant activity

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  2. #2
    markshine is offline Newbie
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    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.


  3. #3
    Nathan John is offline Newbie
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    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.

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