The Fat-Soluble Vitamins

1
Chapter 10

• The Fat-Soluble Vitamins

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Vitamin A Carotenoids

• Sources
• Retinoids - liver, dairy, fish
• Carotenoids - brightly colored fruits
  vegetables
• ?-carotene - greatest provitamin A activity

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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

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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

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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

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Vitamin A Carotenoids

• Functions mechanisms of action
• Vitamin A
• Vision - rhodopsin
• Cellular differentiation
• Gene expression
• Growth
• Other functions - reproduction, bone metabolism

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Vitamin A Carotenoids

• Carotenoids
• Antioxidant functions
• Carotenoids eye health
• Carotenoids heart disease
• Cell proliferation, growth, differentiation
• Carotenoids cancer
• Carotenoids health claims

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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

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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

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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

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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

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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

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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

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Vitamin D

• Interactions with other nutrients
• Calcium, phosphorus, vitamin K
• Metabolism excretion
• Metabolites excreted in feces (gt70) urine
• Adequate Intake (may be inadequate)
• 6 mo-50 years 5 µg or 200 IU
• 51-70 years 10 µg (400 IU) gt70 15 µg (600 IU)

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Vitamin D

• Deficiency rickets osteomalacia
• Rickets - children seizures, growth retardation,
  bones dont mineralize
• Osteomalacia - adults bone mineralization
  defects
• Toxicity
• UL 50 µg (2,000 IU)
• Assessment of nutriture
• Plasma concentration of 25-OH D3

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Vitamin E

• Sources
• Plant oils (canola, olive, sunflower, safflower,
  cottonseed), whole grains, legumes, some fruits
  vegetables
• High-fat meats (inferior)

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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

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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

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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

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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

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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

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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

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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

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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

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Perspective 10

• The Antioxidant Nutrients, Reactive Species,
  Disease

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Antioxidant Nutrients

• Free radical chemistry
• Generation of reactive species
• The superoxide radical
• Hydrogen peroxide
• The hydroxyl radical
• Peroxyl, hydroperoxyl, carbon-centered radicals
  lipid peroxides

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Antioxidant Nutrients

• Singlet molecular oxygen
• Nitric oxide
• Peroxynitrite
• Nitrogen dioxide peroxynitrate
• Damage due to reactive species
• Antioxidant nutrient functions
• Elimination of superoxide radicals

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Antioxidant Nutrients

• Elimination of hydrogen peroxide
• Elimination of hydroxyl radicals
• Elimination of peroxyl, hydroperoxyl,
  carbon-centered radicals, lipid peroxides
• Elimination of singlet molecular oxygen

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Antioxidant Nutrients

• Regeneration of antioxidants
• Vitamin E regeneration
• Ubiquinol (coenzyme QH2) thioredoxin
  regeneration
• Glutathione regeneration
• Vitamin C regeneration
• Antioxidants disease