Notes on Fat Soluble Vitamins

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Department
Food Science and Human Nutrition
Course Code
HUN 2201
Professor
All

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• HUN­ Fat soluble vitamins • Vitamin A o Retinoids: preformed o Carotenoids: proformed  Beta carotene in supplements better absorbed than in food o Function  Vision • Maintenance of the cornea • Component of rhodopsin o In rod cells Converts light impulses to nerve impulses o Dim light; black and white images o Also important for color vision  Cell Differentiation • Activates receptors in stem cells o Epithelial cells, maintains integrity of skin and membranes  Regulation of gene expression • Enters cells • Binds to receptor • Binds to DNA • Controls transcription, regulating differentiation  Growth and bone development • Differentiation o RED BLOOD CELLS • Bone growth and remodeling  Immunity • Maintains epithelial health  Antioxidant • Carotenoids only o Food sources  Retinoids • Liver, fish oils, eggs • Fortified milk and cereals  Carotenoids • Vegetables [dark green, orange, deep yellow] • Some fruits  Stable in cooking o Deficiency  Reduced disease resistance  Night blindness, permanent blindness [xerophthalmia]  Keratinization of tissues • Epithelial cells die and secrete keratin, rather than mucus  Growth retardation o Excess  Retinoids [preformed] only • Permanent liver, bone, eye damage • Birth defects  Pharmacological use • Retinitis pigmentosa • Acute promyelocytic leukemia • Skin disorders [psoriasis, acne] o Nutrient interactions  Zinc deficiency • Interferes with vitamin A metabolism o Retinol binding protein decreases o Release of vitamin A from liver o Retinol to retinal conversion • Iron o Vitamin A deficiency exacerbates iron deficiency o Iron deficiency alters vitamin A levels o Vitamin D  Forms  • D3 = cholecaliciferol • 25, hydroxycholecalciferol [liver] • 1, 25 – dihydroxycholecalciferol [kidney] = 1,25 (OH2)D3 (calcitriol )  [active form]  Synthesis occurs in skin upon exposure to UV light  Functions as a hormone  1. Activates absorption of calcium in the intestine, increasing calcium blood  levels  2. Bone breakdown, leave calcium in blood  3. Kidneys resorb calcium, less lost in the urine • Functions o Also acts in gene expression o Genomic action in intestine:  Turns  • Sources: o Eggs, liver, salmon, chicken, milk • Concern among people with dark skin pigmentation, people who live in  polluted cities,   Deficiency • Improperly absorbed calcium • Growth abnormalities and growth retardation  Excess • Supplementation can cause hypercalcification or deposition of calcium  in different tissues [heart, kidneys, blood vessels] o Vitamin E  Alpha tocopherol: most active, although several forms are found in foods  Fat­soluble molecule, reminiscent of fatty acid chain  Antioxidant nutrient, selenium, carotenoids, vitamin E  Protecting lipids from oxidative damange  Important in tissues where there is a lot of oxygen, like the lungs.  Highly  reactive unpaired electron, can be passed to another molecule and start a  spontaneous chain reaction  Vitamin E in cell membrane stops spontaneous chain reaction  *double bonds of mono and polyunsaturated lipids highly susceptible to  oxidation • Vitamin E can also interact with vitamin C and recharge to its original  state and accept another electron  Deficiency • Hemolytic anemia • UL, although relatively nontoxic • High levels of supplementation INTERFERES WITH VITAMIN K, so  people on blood thinners ought to avoid vitamin E supplements • Spinach, broccoli, avocado NOT ROASTED ALMONDS because they  are heat sensitive o Vitamin K  Forms • Phylloquinones (plants) • Menaquinones (animals, bacteria) • Menadione (synthetic)  Bacteria in gut make vitamin k • Absorption is poor in colon, inadequate for need
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