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Chapter 10

Chapter 10. The Fat-Soluble Vitamins. Vitamin A & Carotenoids. Sources Retinoids - liver, dairy, fish Carotenoids - brightly colored fruits & vegetables -carotene - greatest provitamin A activity. Vitamin A & Carotenoids. Digestion & absorption Vitamin A requires digestion

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Chapter 10

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  1. Chapter 10 The Fat-Soluble Vitamins 2009 Cengage-Wadsworth

  2. Vitamin A & Carotenoids • Sources • Retinoids - liver, dairy, fish • Carotenoids - brightly colored fruits & vegetables • -carotene - greatest provitamin A activity 2009 Cengage-Wadsworth

  3. Vitamin A & Carotenoids • Digestion & absorption • Vitamin A requires digestion • Retinol bound to fatty acid esters • Retinyl esters & carotenes often complexed with protein • Emulsification of fat globules • Retinol absorbed via protein carrier • Carotenoids absorbed via transporters & passive diffusion 2009 Cengage-Wadsworth

  4. Vitamin A & Carotenoids • Carotenoids & retinoids metabolized in enterocytes to some extent • Retinol esterified & incorporated into chylomicrons for transport • Cellular retinol-binding protein (CRBP) II • Transport, metabolism, & storage • Chylomicrons carry to liver • Additional metabolism in liver 2009 Cengage-Wadsworth

  5. Vitamin A & Carotenoids • Retinol that is esterified may be stored in the liver • Stellate cells & parenchymal cells • Transported in blood via 2 proteins • Retinol-binding protein (RBP) • Tranthyretin (TTR) • Carotenoids transported as part of lipoproteins • Carotenoids stored in liver & adipose 2009 Cengage-Wadsworth

  6. Vitamin A & Carotenoids • Functions & mechanisms of action • Vitamin A • Vision - rhodopsin • Cellular differentiation • Gene expression • Growth • Other functions - reproduction, bone metabolism 2009 Cengage-Wadsworth

  7. Vitamin A & Carotenoids • Carotenoids • Antioxidant functions • Carotenoids & eye health • Carotenoids & heart disease • Cell proliferation, growth, & differentiation • Carotenoids & cancer • Carotenoids & health claims 2009 Cengage-Wadsworth

  8. Vitamin A & Carotenoids • Interactions with other nutrients • Vitamins E & K • Protein & zinc • Iron • Metabolism & excretion • Retinol is oxidized & conjugated to make polar, water-soluble metabolites • Excreted in urine (60%), lungs, feces • Carotenoids metabolized to variety of compounds & excreted into bile 2009 Cengage-Wadsworth

  9. Vitamin A & Carotenoids • Recommended Dietary Allowance • 1 RAE = 1 µg retinol = 12 µg -carotene = 24 µg -carotene or -cryptoxanthin • Men: 900 µg RAE; women: 700 µg RAE • Pregnancy: 770 µg RAE; lactation: 1,300 µg RAE • UL = 3,000 µg RAE 2009 Cengage-Wadsworth

  10. Vitamin A & Carotenoids • Deficiency • Xerophthalmia, keratinization • Toxicity: hypervitaminosis A • Assessment of nutriture • Conjunctival impression cytology (CIC) • Plasma retinol concentrations • Relative dose response (RDR) test or modified RDR test 2009 Cengage-Wadsworth

  11. Vitamin D • Sources • Liver, beef, veal, eggs, dairy, some saltwater fish • Synthesis in skin • Absorption, transport, & storage • Dietary D absorbed in micelle • Incorporated into chylomicron for transport 2009 Cengage-Wadsworth

  12. Vitamin D • Cholecalciferol diffuses from skin into blood & picked up by vitamin D-binding protein (DBP) for transport • Metabolized to 25-OH D3 in liver • 25-OH D3 secreted into blood, transported by DBP • Kidneys convert to 1,25-(OH)2 D3 (calcitriol) • Calcitriol trasported in blood via DBP 2009 Cengage-Wadsworth

  13. Vitamin D • Functions & mechanisms of action • Calcium homeostasis • Calcitriol & the intestine • Calcitriol & the kidney • Calcitriol, 24R,25-(OH)2 D3, & the bone • Cell differentiation, proliferation, & growth • Other roles - BP, autoimmune disorders, insulin secretion 2009 Cengage-Wadsworth

  14. Vitamin D • Interactions with other nutrients • Calcium, phosphorus, vitamin K • Metabolism & excretion • Metabolites excreted in feces (>70%) & urine • Adequate Intake (may be inadequate) • 6 mo-50 years: 5 µg or 200 IU • 51-70 years: 10 µg (400 IU); >70: 15 µg (600 IU) 2009 Cengage-Wadsworth

  15. Vitamin D • Deficiency: rickets & osteomalacia • Rickets - children: seizures, growth retardation, bones don’t mineralize • Osteomalacia - adults: bone mineralization defects • Toxicity • UL = 50 µg (2,000 IU) • Assessment of nutriture • Plasma concentration of 25-OH D3 2009 Cengage-Wadsworth

  16. Vitamin E • Sources • Plant oils (canola, olive, sunflower, safflower, cottonseed), whole grains, legumes, some fruits & vegetables • High-fat meats (inferior) 2009 Cengage-Wadsworth

  17. Vitamin E • Digestion, absorption, transport, & storage • Tocotrienols hydrolyzed; synthetic ester forms digested • Absorbed primarily in jejunum by non-saturable, passive diffusion • Chylomicrons for transport • Liver recirculates some in VLDL • Stored mostly in adipose tissues 2009 Cengage-Wadsworth

  18. Vitamin E • Functions & mechanisms of action • Antioxidant role • Free radical termination • Singlet molecular oxygen destruction • Other roles • Vitamin E & heart disease • Vitamin E & eye health • Other conditions 2009 Cengage-Wadsworth

  19. Vitamin E • Interactions with other nutrients • Selenium, vitamin C • Sulfur-containing AAs • Polyunsaturated FAs • Metabolism & excretion • Several metabolites excreted in urine • Major route is feces via bile 2009 Cengage-Wadsworth

  20. Vitamin E • Recommended Dietary Allowance • Adults (including pregnancy): 15 mg -tocopherol • Lactation: 19 mg -tocopherol • Deficiency • Toxicity • UL = 1,000 mg -tocopherol • Assessment of nutriture • Plasma concentrations • Erythrocyte hemolysis test 2009 Cengage-Wadsworth

  21. Vitamin K • Sources • Leafy green vegetables, legumes • Bacterial synthesis • Absorption, transport, & storage • Phylloquinone absorbed in small intestine in micelles • Menaquinones absorbed by passive diffusion from ileum & colon 2009 Cengage-Wadsworth

  22. Vitamin K • Transported in chylomicrons, LDL • Stored in liver & other tissues • Functions & mechanisms of action • Vitamin K & blood clotting • Overview of blood clotting • The role of vitamin K in carboxylation of glutamic acid residues • Vitamin K & bone & nonosseous tissue proteins 2009 Cengage-Wadsworth

  23. Vitamin K • Interactions with other nutrients • Vitamins A & E • Vitamins D & A • Metabolism & excretion • Phylloquinone metabolites excreted primarily in feces & in urine • Menaquinone thought to be metabolized & excreted in bile & urine 2009 Cengage-Wadsworth

  24. Vitamin K • Adequate Intake • Men: 120 µg; women: 90 µg • Deficiency • Newborns, malabsorption, antibiotics • Toxicity - synthetic menadione • Assessment of nutriture • Plasma or serum phylloquinone • Blood clotting or prothrombin time • Undercarboxylated vitamin K-dependent proteins 2009 Cengage-Wadsworth

  25. Perspective 10 The Antioxidant Nutrients, Reactive Species, & Disease 2009 Cengage-Wadsworth

  26. Antioxidant Nutrients • Free radical chemistry • Generation of reactive species • The superoxide radical • Hydrogen peroxide • The hydroxyl radical • Peroxyl, hydroperoxyl, & carbon-centered radicals & lipid peroxides 2009 Cengage-Wadsworth

  27. Antioxidant Nutrients • Singlet molecular oxygen • Nitric oxide • Peroxynitrite • Nitrogen dioxide & peroxynitrate • Damage due to reactive species • Antioxidant nutrient functions • Elimination of superoxide radicals 2009 Cengage-Wadsworth

  28. Antioxidant Nutrients • Elimination of hydrogen peroxide • Elimination of hydroxyl radicals • Elimination of peroxyl, hydroperoxyl, & carbon-centered radicals, & lipid peroxides • Elimination of singlet molecular oxygen 2009 Cengage-Wadsworth

  29. Antioxidant Nutrients • Regeneration of antioxidants • Vitamin E regeneration • Ubiquinol (coenzyme QH2) & thioredoxin regeneration • Glutathione regeneration • Vitamin C regeneration • Antioxidants & disease 2009 Cengage-Wadsworth

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