Fat Soluble Vitamins Flashcards
Fat soluble vitamins
Lipid soluble
in the presence of fat
Absorption and transport is similar to fat
Can be stored
Can be toxic in high doses
Vitamin E
Alpha tocopherol
Vitamin E Function
Antioxidant
Protect unsaturated FA
Vitamin E Absorption and transport
Emulsion with bile acids
Incorporate into chylomicrons for circulation
Processed in the liver
Vitamin E Storage and excretion
Excrete via bile and feces
Can excrete in urine after processing in liver
Vitamin E deficiency
Rare
Result of insufficient fat absorption
Linked to maintenance of cell membranes
Erythrocyte hemolysis
Vitamin E deficiency symptoms
Retinopathy
Peripheral neuropathy
Ataxia
Lower immune function
Erythrocyte hemolysis
(breakdown of RBC)
Vitamin E food sources
Widely available
Vegetable oils
Destroyed by heat and oxidation
Vitamin E toxicity
Interference with blood clotting
Rare
Vitamin A
Retinoids
Vitamin A Function
Required to form rhodopsin in the rod cell photoreceptors
Regulation of gene expression
Vitamin A sources
Preformed and dietary sources
Vitamin A pre formed sources
Animal products
Liver
Dairy
Egg
Fish
Fortified foods
Vitamin A dietary sources
Beta carotene
Sweet potatoes
Carrots
Alpha carotene
Beta cryptoxanthin
Conversion of pro vitamins
Requires BCO1
Converts beta carotene into retinal
Not perfect efficiency
Depends on bioavailability
Vitamin A absorption and transport
Vitamin A as retinyl esters
Absorbed in SI
Need dietary fat and bile acids
Must be de-esterified to be absorbed
De-esterify → absorb → esterify → chylomicrons → circulate
Vitamin A as pro vitamin A
Lower absorption
Processing can increase absorption
Still requires dietary fat
Vitamin A after absorption
Metabolized in enterocytes before entering bloodstream
Vitamin A interconversion
Retinyl esters ←→ retinol ←→ retinal ←→ retinoic acid
Beta carotene converted to retinal
Retinoic acid = active form
Vitamin A transport and storage
Retinyl esters can be stored in hepatic stellate cells
Retinol binds to retinol binding protein
Forms holo RBP
Deliver retinol to other tissues
Excrete in bile and kidneys
Vitamin A RDA
In retinol activity equivalents
Higher for pregnancy and lactating
Vitamin A deficiency
Night blindness
Xerophthalmia (dryness)
Bitot spots
Poor growth
Increased susceptibility to infection
Vitamin A toxicity
Acute and chronic
Vitamin A toxicity - acute
Single excessive dose
Nausea
Headache
Double vision
Vomiting
Vitamin A toxicity - chronic
3-4 x RDA
Anorexia
Hair loss
Skin problems
Increased bone fractures
Eye pain
Liver damage
Birth defects
Vitamin K
Phylloquinone
Vitamin K function
Blood clotting
Essential for activation of proteins that participate in clotting process
Bone calcification
Gamma carboxylation
Clotting factors require Ca binding to be active
Gamma carboxylation provides this ability
Adds carboxylic acid group to glutamate → allow for Ca binding
Vitamin K drug interaction
Blood thinner
Warfarin interfere with recycling of vitamin K
Makes it less available, reduce gamma carboxylation
Vitamin K transport, absorption
Absorbed in SI
Requires fat, bile acids
Supplements are more bioavailable
Transported in chylomicrons
Vitamin K storage, transport
Limited storage
Use reducing power (Nadph) to recycle
Vitamin K RDA
No UL, toxicity
Interfere with anticoagulants
Vitamin K deficiency
Primary deficiency is rare
Secondary deficiency
Malabsorption
Anticoagulants
Hemmorages
Vitamin K food souces
Green, leafy veg
Gut bacteria
Vitamin D food sources
Animal products
Liver
Beef
Veal
Eggs
Sun contact
Fortified foods
Milk
OJ
Breads
Vitamin D absorption
About 50% efficient
Occurs in SI
Incorporated into micelles
Packaged into chylomicrons to circulate
Circulates bound to vitamin D binding protein
Vitamin D activation
Two step activation
Liver (add OH)
Kidneys (add OH)
Final product = calcitriol, active vitamin D
Vitamin D synthesis factors
Amount of radiation
Age
Race
Clothing
Sunscreen
calcitriol, active vitamin D
Regulates its own breakdown via negative feedback
Made where it is used
Potent gene expression regulator
Vitamin D function
Maintain serum calcium/phosphorus levels
Behaves as a hormone
Immune system
Bone health
Low Ca 2+ levels
PTH released from parathyroid gland
PTH activates enzymes in kidney that convert vitamin D to active form
PTH and active vitamin D demineralize bone to release calcium and phosphorus into blood
Active vitamin D increases calcium absorption from intestine and reabsorption from kidneys
High Ca 2+ levels
Calcitonin released from thyroid
Stimulate addition of Ca and phosphorus to build bone
Vitamin D hormone
Regulates gene expression by binding to vitamin D receptor
Nuclear receptor has broad functions
Vitamin D immune system
Influence immune response and host defense against pathogens
Vitamin D bone health
Calcitriol facilitate calcium absorption from gut
Increase expression of calbindin and calcium channels
Similar effects on renal tubules
Vitamin D recommendations
Older adults need more
15 mins of sunlight a day
Vitamin D deficiency
Inadequate calcium and phosphorus deposition in bone
Osteomalacia
Rickets
Osteomalacia
Soft bones
In adults
Caused by kidney/stomach/gallbladder/intestinal/liver disease affecting vitamin D metabolism/absorption
Rickets
In kids
Bowed legs
Enlarged head and rib cage
Deformed pelvis
Vitamin D toxicity
Nearly impossible
Results from excess supplementation
Vitamin D toxicity symptoms
Hypercalcemia
(Calcification of tissues)
Kidney dysfunction
Loss of appetite
GI stress
