The Fat Soluble Vitamins A D E and K Chapter 11 Dr Alisha Rovner NTDT200 Fall 2013 Introduction Differences between fat soluble vitamins and water soluble vitamins Insoluble in watery GI juices so require bile for digestion and absorption Travel through lymphatic system Many require transport proteins in bloodstream Excesses are stored primarily in liver and adipose tissu Can eat less than daily needs without ill effects Not readily excreted so risk of toxicity is greater Vitamin A and Beta Carotene Vitamin A 1st fat soluble vitamin recognized Precursor beta carotene Three different forms Retinol Retinal Retinoic acid Vitamin A and Beta Carotene Digestion and absorption of vitamin A Several proteins participate Storage After absorbed via lymph system it arrives in the liver where it s stored Transport protein Retinol binding protein RBP picks it up from the liver and carries it in the blood Cellular receptors for vitamin A Cells that use vitamin A have special protein receptors Vitamin A and Beta Carotene Roles in the Body Major roles Promoting vision Participating in protein synthesis and cell differentiation thereby maintaining the health of epithelial tissues and skin Supporting reproduction and growth Vitamin A and Beta Carotene Roles in the Body Retinol Supports reproduction Major transport and storage form Retinal Active in vision Retinoic acid Regulates cell differentiation growth and embryonic development Vitamin A and Beta Carotene Roles in the Body Vision Plays indispensable roles in eye Helps maintain cornea Participates in conversion of light energy into nerve impulses at the retina Vitamin A and Beta Carotene Roles in the Body Protein synthesis cell differentiation Epithelial cells cells on surface of skin and mucous membranes Helps protect against skin damage from sunlight Promotes differentiation of epithelial cells and goblet cells secrete mucous Vitamin A and Beta Carotene Roles in the Body Reproduction and growth In men participates in sperm development In women supports normal fetal development Growth of children Bone remodeling Antioxidant Beta carotene serves primarily as vitamin A precursor Vitamin A and Beta Carotene Vitamin A Deficiency Vitamin A status Depends mostly on adequacy of stores 90 stored in liver Depends on protein status because RBP serves as vitamin s transport carrier Consequences of deficiency Risk of infectious diseases Blindness Death Vitamin A and Beta Carotene Vitamin A Deficiency Infectious diseases Measles severity Malaria lung diseases and HIV Night blindness Inadequate supply of retinal to retina Blindness xerophthalmia Lack of vitamin A at the cornea Develops in stages Vitamin A Deficiency Symptom Night Blindness Vitamin A and Beta Carotene Vitamin A Deficiency 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 Deficiency Symptom The Rough Skin of Keratinization 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 Vitamin A and Beta Carotene Vitamin A Toxicity Beta carotene Found in many fruits and vegetables Inefficient conversion Overconsumption from food Yellow skin Overconsumption from supplements Antioxidant becomes prooxidant Alcohol consumption and tobacco use Symptom of Bet Carotene Excess Discoloration of Skin Vitamin A and Beta Carotene Vitamin A Toxicity Bone defects May weaken bones Osteoporosis Interferes with vitamin D Birth defects Cell death in the spinal cord Acne Vitamin A relative Retin A Vitamin A and Beta Carotene Recommendations Expressed as retinol activity equivalents RAE Supplements often measured in International Units IU Vitamin A and Beta Carotene Food sources Animal sources Liver and toxicity concerns Plant sources Vitamin A precursors Bioavailability Colors of food Vitamin A in Selected Foods Vitamin D Not an essential nutrient Body synthesizes Sunlight Precursor from cholesterol Activation of vitamin D Two hydroxylation reactions Liver Kidneys Vitamin D Synthesis and Activation Vitamin D Roles in the Body Active form of vitamin D is a hormone Binding protein carries it to target organs Bone growth Calcium and phosphorus absorption Enhances absorption Provides minerals from other sources Other roles Enhances or suppresses gene activity Vitamin D Deficiency Overt signs are relatively rare Insufficiency is quite common Contributory factors Dark skin breastfeeding without supplementation lack of sunlight not consuming fortified milk Creates a calcium deficiency Vitamin D Deficiency Rickets Bones fail to calcify normally Bones bend Affects children Osteomalacia Poor mineralization of bones Affects adults Bones are soft flexible brittle and deformed Vitamin D Deficiency Symptoms Rickets Vitamin D Deficiency Osteoporosis Loss of calcium from bones Results in fractures Elderly Vitamin D deficiency is especially likely Lose ability to make and activate vitamin D Drink less milk Spend much of day indoors Vitamin D Toxicity Most likely of the vitamins to have toxic effects Raises blood calcium concentrations Forms stones in soft tissues May harden blood vessels Can cause death Vitamin D Recommendation Sources Few food sources Oily fish and egg yolks Fortified milk Recommendations may be insufficient Recommendations are difficult to meet Sun exposure No risk of toxicity Skin color latitude season time of day Sunscreen Vitamin D Synthesis and Latitude Vitamin E Four different tocopherol compounds Alpha beta gamma and delta Position of methyl group Alpha tocopherol vitamin E activity in the body Antioxidant Stop chain reaction of free radicals Protect cells and their membranes Heart disease and protection of LDLs Vitamin E Deficiency Primary deficiency is rare Secondary deficiency Fat malabsorption Effects of deficiency Red blood cells break open Erythrocyte hemolysis Neuromuscular dysfunction Other conditions and vitamin E treatment Vitamin E Toxicity Liver regulates vitamin E concentrations Toxicity is rare UL is 65 times greater than recommended intake for adults Extremely high doses of vitamin E May interfere with vitamin K activity Hemorrhage Vitamin E Recommendations Foods RDA is based on alpha tocopherol only U S intakes tend to
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