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Fat Soluble Vitamins (week 7).docx

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Queen's University
Health Studies
HLTH 230
Jeffery Lalonde

Fat Soluble Vitamins  A, D, E, K o Fat soluble vitamins require bile for absorption o They travel through the lymphatic system on absorption before entering the blood stream  Many fat soluble vitamins require protein carrier for transport in the bloodstream o Excesses are stored in the liver and adipose tissue  Body maintains blood concetration by getting fat soluble vitamins from storage as needed  People can go without their needed amount for days as long as average intake meets their needs o Toxicity is more likely because of their storage and because they are not readily excreted Vitamin A and Beta- Carotene  Vitamin A o Precursor is beta – carotene  Vitamin A has 3 active forms o Retinoids  Retinol  Retinal  Retinoic Acid  Foods from animals can provide retinyl esters which can be digested and absorbed into retinol in the intestine  Cells can convert retinol and retinal to other active forms of Vitamin A as needed  Conversion from retinol and retinal is reversible  Retinal to retinoic acid is not  Irreversible change is important because each form of Vitamin A has unique function  Foods from plants can provide carotenoids o Precursors to Vitamin A  Vitamin A activity  A carotene  B carotene  B thin  No vitamin A activity  Lycopene  Lutein  Zthin  Beta Carotene o Centre cleavage of beta carotene can provide 2 molecules of Vitamin A o Cleavage can occur at other locations but only yielding 1 vitamin A molecule  Absorption of beta carotene is less efficient than Vitamin A  12 micrograms of beta carotene is equal to 1 microgram of vitamin A  12:1  Conversion from other carotenoids is less efficient  Absorption and Transport of Vitamin A in the Body o Absorbed into the lymph system  Fat soluble o Stored in the liver  Retinol Binding Protein picks up Vitamin A in the liver and carries it through the blood sream  Cells that use vitamin A have special protein receptors for it Major Roles  Promote vision o Helps maintain cornea o Participates in conversion of light energy to nerve impulses in the retina o The cis bonds in the eye change to trans bond when Rhodopsin absorbs light o Triggers visual information to the brain  Light passes through cornea and strikes cells of retina  Rhodospin changes shape and becomes bleached  Change to trans bond  Nerve impulse sent to brain  Visual activity leads to repeated loss of retinal and constant replenishment  Only 1/1000 thof body’s vitamin A is in the retina o Rhodospin  Pigment molecules composed of ospin (protein) bonded to a molecule of retinal  Protein synthesis and differentiation o Cell differentiation  A process by which types of cells develop to perform specific functions o Epithelial Cells  All body surfaces covered by these cells  The outside – skin  The inside – mucous membrane  Vitamin A maintains health cells in the mucous membrane  Promotes differentiation of both epithelial cells and goblet sells  The cells that synthesize and secrete mucuous  Vitamin A in Reproduction and Growth o Retinol  Participates in sperm development o Vitamin supports normal fetal growth and development during pregnancy  Children who lack vitamin A fail to grow o Vitamin A participates in bone remodeling for growth  Assists enzymes in breaking down parts of the bone to allow it for growth  Bone Remodeling  The dismantling and reformation of bone  Beta Carotene as an Antioxidant o Acts as a precursor for Vitamin A o Some may not be converted into vitamin A and may act as an antioxidant helping to protect the body against disease Deficiency  Vitamin A status depends on liver storage and protein status o (RBP)Retinol Binding Protein  Carrier for vitamin A in the body  Deficiency occurs more quickly in a growing child o Would take adult 2 years for vitamin stores deplete o Major problem in developing countries  Infectious Disease o Body’s defences depend on vitamin A o Severity of illness correlates with vitamin A deficiency  Night Blindness o First detectable sign of vitamin A deficiency  Early diagnosis o Retina does not receive enough retinal to regenerate  Person adopts to bright lights slowly  Total Blindness (Xerophthalmia) o Night blindness caused by a lack of Vitamin A at the back of the eye  Retina o Total blindness is casued by lack of vitamin A in the front of the eye  Cornea  First sign of blindness is xerosis  Cornea becomes dry and hard  Xerosis changes to keratomalcia  Softening of the cornea which leads to irreversible blindness o Xerophtalmia  Keratinization o The body’s outer surface secrets keratin o Keratin  Hard, inflexible proteins  Hair, nails o Accumulation of keratin in the tissue causes skin to become dry, rough and lumpy  Also affects other surfaces o Goblet cells in GI tract decrease in number and activity  Less mucous is therefore secreted  Normal digestion and absorption of nutrients is decreased worsening malnutrition o Epithelial tissues defences weakens  Easier infection of GI, respitory tract, vagina, and inner ear Toxicity  From large amounts of vitamin A from animal foods, fortified foods, or supplments  Cannot occur from Beta Carotene o Beta carotene from food is not converted efficiently enough into vitamin A to cause toxicity  Excess can be stored under the skin  Causes orange skin o Beta carotene supplements can be harmful  Anti oxidant can act as a pro oxidant  Promotes cell division and destroys Vitamin A  Bone Defects o Excess amounts of vitamin A can contribute to osteoporosis and factures by weakening the bones  Bone building activity is suppressed  Bone dismantling activity is stimulated  Vitamin A interferes with Vitamin D and its ability to maintain blood calcium levels  Birth Defects o Excess vitamin A can be teratogenic  Causes abnormal fetal development and birth defects  Intakes of over 10,000 IU supplements daily in early pregnancy  Not for Acne o Accutane comes from Vitamin A, but not the same as taking extra Vitamin A o Hypervitaminosis A  Liver abnormalities and reduced bone density  Chronic o Acute symptoms  Blurred vision, nausea, headaches Recommendations  1 microgram of retinol = 1 RAE (retinol activity equivalent)  12 micrograms of dietary beta carotene = 1 RAE Destruction and loss of Vitamin A  Lost when milk is skimmed o Milk is generally fortified Vitamin A in foods  Fish, liver, liver oil, butter, eggs Beta carotene has the highest vitamin A activity of all carotenoids  Dark green leafy vegetables  Rich yellow and deep orange fruits and vegetables Pour sources  White plant foods o Cauliflower o Potatoes, fast foods Vitamin D  Other Name : Calciferol o Non essential nutrient  Body can make it with help
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