PUBH 1517 - Vitamins D,E & K

PUBH 1517 - Vitamins D,E & K - Vitamin D:...

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Unformatted text preview: Vitamin D: Calciferol Vitamin Ultraviolet light on skin converts 7-dehydrocholesterol to cholecalciferol, the cholesterol provitamin form (D3) provitamin Side-chain reaction in liver yields 25hydroxycholecalciferol Final activation step in kidney, yielding Final 1,25-dehyroxyvitamin D3 1,25-dehyroxyvitamin Activation regulated by PTH, which is Activation secreted in response to low plasma calcium level Functions of Vitamin D Functions Maintenance of Ca and P homeostasis Enhances active transport of Ca across Enhances gut by stimulating synthesis of calciumgut binding protein in brush border. Also binding stimulates intestinal phosphate transport. stimulates Together with PTH & estrogen, regulates Together mobilization & deposition of Ca & P in bones bones In kidney, increases reabsorption of both In kidney increases Ca and phosphate Ca Possible Functions of Vitamin D Possible May be essential for Cell differentiation Functional maintenance of membranes Functions of skin, muscles, pancreas, Functions nerves, parathyroid gland, & immune system DRI for Vitamin D DRI Adequate Intake 5 ug/day for children & adults < 51 ug/day years years 10 ug/day for adults age 51 to 70 15 ug/day for adults age 71 and up Upper limits 25 ug/day for infants (1000 IU) 50 ug/day for children & adults (2000 50 Sources of Vitamin D Sources Synthesis adequate in body with enough sun Food Vitamin D (ug) 1 ug = 40 IU Herring, fresh, raw, 1oz Fortified milk, 1c 6.4 6.4 2.5 2.5 Chicken liver, 3oz 1.1 1.1 Egg yolk .63 .63 Vitamin D Deficiency Vitamin Rickets in children: impaired mineralization of growing bones results in soft bones that deform as in bowed legs and beaded ribs deform Osteomalacia in adults: reduction of bone density with presence of pseudofractures of spine, femur, humerus. Muscular weakness, bone tenderness. weakness, Can result from prolonged breastfeeding Can without sun exposure or vit D supplements without This child has the Vitamin D deficiency disease rickets Vitamin D Toxicity Vitamin Causes elevated serum calcium & Causes phosphorus phosphorus Ultimate calcification of soft tissue, Ultimate including kidney, lungs, heart, eardrum eardrum Infants may have GI upset, bone Infants fragility, retarded growth fragility, Vitamin D Absorption & Transport Absorption Absorbed with lipids & incorporated into Absorbed chylomicrons chylomicrons Transferred to vitamin D-binding protein Transferred (DBP or transcalciferin) in the plasma (DBP 50% absorption efficiency In cells, bound to vitamin D receptor In proteins (VDRs) proteins Very little stored in liver Partitions into lipid phases of many tissues Partitions Vitamin E: Tocopherol Vitamin Functions: Antioxidant for lipids & lipid-related Antioxidant compounds in cells compounds Especially in lungs, blood cells Deficiency symptoms Premature babies: rupture of red blood Premature cells (erythrocyte hemolysis) cells Adults: loss of muscle coordination & Adults: reflexes with impaired movement reflexes Vitamin E Needs & Sources Needs RDA RDA 15 mg/day for adult men & women Sources Safflower oil, 1 Tbsp Canola oil, 1 Tbsp Sunflower seeds, 1 Tbsp Wheat germ, 1 oz 4.8 mg 2.3 mg 7.7 mg 4.8 mg Distribution of Vit E in Diet Distribution 20% from vegetable oils & related 20% products products 20% from fruits & vegetables 15% from fortified cereals & other 15% grain products grain Remainder from mix of other foods, Remainder but animal fats have almost none but Vitamin E Toxicity Vitamin Large doses may augment effects of Large anticoagulant medication anticoagulant Upper limit: 1000mg/day Note: Information about vitamin E Information content may give units as alpha tocopherol equivalents (TE). To convert TE to mg, multiply by 0.8. convert Vitamin K Vitamin Functions Functions Essential for blood clotting, because is Essential needed for synthesis of proteins that help clot the blood clot Necessary for synthesis of key protein Necessary needed in bone formation (for binding of minerals) minerals) Possible role in reducing risk of hip fracture Possible (based on study of women which showed lower risk with high green vegetable intake) lower Vitamin K Needs & Sources Needs AI (2001): AI 120 ug for men 90 ug for women 90 Sources Synthesized by intestinal bacteria (probably Synthesized supplies ½ daily need) supplies Highest amts: dark green leafy vegetables, Highest including green tea (50 to 800 ug) & members of cabbage family, liver cabbage Present in smaller but significant amounts in other Present foods such as meats, eggs, cereals, fruits Vitamin K Deficiency & Toxicity Deficiency Deficiency usually only occurs in individuals with little or no intestinal bacteria: newborn infants, antibiotic users infants, Deficiency Symptoms: poor clotting poor Toxicity Symptoms: Toxicity Breakage of red blood cells with release of Breakage bilirubin, causing jaundice & potential brain damage &/or death of an infant damage Vitamin K Precautions & Misc. Info Precautions Toxic levels easily reached with supplements, so the single vitamin is only available by prescription prescription Drug interaction: Coumadin users need to Coumadin avoid high vitamin K intake, because it counteracts the anticoagulant effect of the drug drug Amounts in food: analysis techniques under analysis revision. Not included in food comp tables. revision. ...
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