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

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

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

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

 2009 Cengage-Wadsworth 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 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 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 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 Vitamin D –Cholecalciferol diffuses from skin into blood & picked up by vitamin D- binding protein (DBP) for transport –Metabolized to 25-OH D 3 in liver –25-OH D 3 secreted into blood, transported by DBP –Kidneys convert to 1,25-(OH) 2 D 3 (calcitriol) –Calcitriol trasported in blood via DBP

 2009 Cengage-Wadsworth Vitamin D Functions & mechanisms of action –Calcium homeostasis Calcitriol & the intestine Calcitriol & the kidney Calcitriol, 24R,25-(OH) 2 D 3, & the bone –Cell differentiation, proliferation, & growth –Other roles - BP, autoimmune disorders, insulin secretion

 2009 Cengage-Wadsworth 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 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 D 3

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

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

 2009 Cengage-Wadsworth 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 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 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 Antioxidant Nutrients Regeneration of antioxidants –Vitamin E regeneration –Ubiquinol (coenzyme QH 2 ) & thioredoxin regeneration –Glutathione regeneration –Vitamin C regeneration Antioxidants & disease