Exam 3 Nutrition Concepts The Fat-Soluble Vitamins: A, D, E, and K Chapter 11 !Introduction • Fat-soluble vitamins differ from water-soluble vitamins • Require bile for digestion and absorption • Travel through lymphatic system • Many require transport proteins in bloodstream • Excesses are stored • Liver and adipose tissue •Needed in periodic doses (weeks or months) • Risk of toxicity is greater !Review of Vitamins Water-Soluble Vitamins vs. Fat-soluble Vitamins - Absorption: - Transport: - Storage: Water= no storage, excreted by kidney when consumed in excess , Fat= liver and adipose tissue - Excretion: Water soluble (by the kidney) -Toxicity: Fat: D and A, Water: Niacin, B6, Folate! (With masking toxicity of B12) -Requirements: !Vitamin A and Beta-Carotene • Vitamin A, first fat-soluble vitamin recognized • All naturally occurring compounds with the biological activity of retinol, the alcohol form of vitamin A • Retinyl esters– form found in animal foods • Carotenoids– form found in plant foods • Beta-carotene: pre-cursor of Vitamin A (most Vitamin C) • Retinoids – in the body • Retinol, Retinal, Retinoic acid !!!Conversion of Vitamin A Compounds !!!!!Exam 3 Nutrition Concepts !!!!!!Vitamin A and Beta-Carotene: Roles in the Body • Major roles • Vision • Protein synthesis and cell differentiation • Maintain health of epithelial tissues and skin • Reproduction and growth • Regulation of gene expression !• Vision • Retinal – forms part of rhodopsin - Much converted back to cis form - Some oxidized to Retinoic Acid L • Visual activity • Repeated small losses of retinal • Need for replenishment with Vitamin A • Epithelial tissue • Skin • Mucous membranes - linings of GI tract, lungs, urinary bladder, urethra, reproductive organs, eyelids, and sinus passageways !• Protein synthesis & cell differentiation • Epithelial cells • Goblet cells • Secrete mucus to protect epithelial cells !• Reproduction and growth • Sperm development • Normal fetal development • Growth of children • Bone remodeling • Antioxidant • Beta-carotene !Review • List the major roles of vitamin A in the body: 1. VisionExam 3 Nutrition Concepts 2. Skin - Protein synthesis and cell differentiation 3. Reproduction and Growth !Additional: antioxidant !Vitamin A and Beta-Carotene= Vitamin A Deficiency • Vitamin A status depends on: • Adequacyofstores • 90% stored in liver ! • Proteinstatus • Retinol-binding protein (RBP) – carries Vitamin A in blood • Consequences of deficiency • Risk of infectious diseases, blindness, death • Infectious diseases • Severity correlates with vit A deficiency • Measles, malaria, lung diseases, and HIV • Night blindness • One of first detectable signs of vit A deficiency – aids diagnosis • Inadequate supply of retinal to retina • Blindness (xerophthalmia) • Lack of vitamin A at the cornea • Develops in stages • Severe Vitamin A deficiency is leading cause of preventable blindness, with half a million preschool children losing sight each year !• Keratinization • Change in shape & size of epithelial cells • Skin becomes dry, rough, and scaly • Normal digestion and absorption of nutrients from GI tract falters • Weakened defenses in respiratory tract, vagina, inner ear, and urinary tract !Vitamin A and Beta-Carotene - Vitamin A Toxicity • Develops when binding proteins are loaded • Free vitamin A damages cells • Toxicity is a real possibility • Preformed vitamin A from animal sources • Fortified foods • Supplements • Children are most vulnerable • Beta-carotene • Found in many fruits and vegetables • Inefficient conversionExam 3 Nutrition Concepts • Over consumption from food • Yellow skin – not harmful • Over consumption from supplements • Antioxidant becomes pro-oxidant • Alcohol consumption and tobacco use ↑ effects of supplementation • Bone defects • May weaken bones • Osteoporosis • Interferes with vitamin D’s ability to maintain blood calcium • Birth defects • Cell death in the spinal cord •Teratogen – substance that causes abnormal fetal development and birth defects !• Prescription medications – effective, but require medical supervision due to possible side effects • Accutane (isotretinoin) • Vitamin A relative – Retin-A, prescription for topical use • Fights acne and wrinkles, lightens pigmented skin !Review • Deficiency is common in developing countries. • Vit A offers protection in the following illnesses: HIV, Malaria, Measles, Lung Disease, warranting supplementation for infants and children with such conditions. • Supplements are also warranted when a deficiency has caused night blindness, one of the first detectable signs of vit A deficiency. !Vitamin A and Beta-Carotene • Recommendations • Expressed as retinol activity equivalents (RAE), mcg, IU • 1 mcg retinol = 1 RAE • 12 mcg beta-carotene = 1 RAE • Supplements often measured in International Units (IU) !Vitamin A Measures 1 mg RAE = 1 mcg retinol = 2 mcg beta-carotene = 12 mcg beta-carotene = 24 mcg other vit A precursor carotenoids !1 IU retinol = .3 mcg retinol = .3 mcg RAE !!Exam 3 Nutrition Concepts Vitamin A and Beta-Carotene • Food sources • Animal sources - retinoids • Liver, fish liver oils • Rich source, frequent consumption can cause toxicity (of active form) • Milk, milk products, butter (skim might not have these because stored in fat and skim is fat free) • Milk must have 1200 IU per quart (level of vit A in whole milk) • Margarine fortified to have level of butter • Eggs !• Food sources • Plant sources - carotenoids • Beta-carotene • Rich, deep yellow, almost orange compound • Cantaloupe, carrots, sweet potatoes • Masked by chlorophyll in dark green, leafy vegetables • Spinach, broccoli !Review • Plants contain carotenoids, vitamin A precursors. Only a few have vitamin A activity; the one with the greatest vitamin A activity is beta-carotene. It is found in fruits & vegetables (food groups) orange in color, such as cantaloupe, carrots, sweet potatoes. It is also found in foods dark green in color such as spinach & broccoli. The chlorophyll in these foods masks the color
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