Vitamins and their roles L3-5_2010Bb

Vitamins and their roles L3-5_2010Bb - Vitamins &...

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Their use Their role in bone metabolism Their role in erythropoiesis
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Section Objectives • Discuss the role of vitamins in normal physiology • Examine : – Mechanism of action (putative) – Pharmacokinetics (important aspects) – Therapeutic Use – Toxicity/Adverse Effects/Interaction • Look at the role between – Vitamin B family & Erythropoiesis
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Terminology • micronutrients vs. macronutrients • microminerals vs. macrominerals (> 100 mg/day) Daily Reference Intakes (DRI) (table 63.1 in text) 1.EAR: average daily nutrient intake level estimated to meet the requirement of 50% of healthy individuals in a specific life stage or gender group used to calculate the RDA
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Dietary Reference Intakes (con’t) 2. RDA: average daily nutrient intake level sufficient to meet the nutrient requirement of nearly all healthy individuals in a specific life stage or gender group ( = EAR + 2 SD EAR ) 3. AI: recommended average daily nutrient intake level 4. UL: highest average daily nutrient intake level likely to pose no risk of adverse health effects to almost all individuals
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Vitamins • organic chemicals that must be supplied by exogenous sources to achieve adequate functional amounts (exception: vitamin D) – lipid soluble: vitamins A, D, E, and K – water soluble: vitamins C and B • primary deficiencies are due to inadequate intake • secondary deficiencies are due to improper absorption, drug-nutrient interactions, and/or increased requirements
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Fat Soluble Vitamins: Vitamin D and role in bone metabolism
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Vitamin A • retinoids: retinol, retinal, retinoic acid, and related compounds – preformed vitamin A (retinol and retinal) or provitamin A carotenoids (ie. β-carotene) • function: important for night vision regulation of gene expression (acts as a hormone) – cellular differentiation (immunity; growth and development)
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Higdon, J. An evidence-based approach to vitamins and minerals: health implications and intake recommendations. Thieme. New York, 2003. Role in Night Vision
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Fig. 1. Intracellular retinoid metabolism, transport, and nuclear action. M. McGrane, J.Nutr. Biochem 2007 Role in Gene Transcription
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Vitamin A • sources: – animals: liver, fish liver oils, milk & dairy products, egg yolk – plants: carotene and β-carotene in green and orange/yellow vegetables and fruits – supplements: retinyl palmitate and retinyl acetate – fortification • β-carotene is less easily absorbed than retinol (must be converted to retinal and retinol)
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Vitamin A: PK • absorption : bile salts enhance retinol absorption and are required for the absorption of β-carotene • transport : vitamin A and β-carotene are transported from the intestine in the chylomicra via the lymph in the same way as fat absorption • storage : mainly in the liver as esters; also in kidney, adipose tissue and lung • regulated process releases vitamin A into the plasma as retinol bound to a specific retinol binding protein (RBP)
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Vitamins and their roles L3-5_2010Bb - Vitamins &...

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