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Fat soluble vitamins
FACS 113
Susan Algert
Fat Soluble Vitamins
• Dissolve in organic solvents
• Not readily excreted and can cause
toxicity
• Fat malabsorption can cause deficiency
• Transported like fat in chylomicrons,
VLDL, LDL and other protein carriers
Vitamins
• Essential organic substances
• Yield no energy, but facilitate energy
yielding reactions
• Will produce deficiency signs and
symptoms if absent from the diet
• Fat soluble and water soluble
Forms of Vitamin A
• Preformed are retinyl esters
retinoids (retinal retinol, retinoic
acid)
found in animal products
Provitamin A
• Carotenoids (beta carotene, alpha
carotene, lutein, lycopene, zeaxanthin)
• Must be converted to retinoid form
• Found in plant products
• Most biologically active provitamin is
beta carotene
Transport and Storage
• Liver stores 90% of vitamin A in the body
• Reserve is adequate for several months
• Transported from the liver as retinol via
retinol binding protein to target tissue
• Caroteinoids can be transported via CM and
VLDL
• Target cells contain intracellular retinol
binding proteins
Vitamin A roles in the body
• Promotes vision (retinol)
• Supports protein synthesis and cell
differentiation (retinoic acid)
• Night and color vision (retinal)
Cartenoids roles in the body
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Antioxidant
Vision
Cancer
Heart disease
The visual cycle
• Cones in the retina
Are responsible for vision under bright light
Translate objects to color vision
• Rods in the retina
responsible for vision in dim light
translate objects in black and white vision
Cell health and maintenance
• Retinoic acid influences how the
epithelial cells differentiate and mature
• Without vitamin A cells will not
differentiate
• Leads to follicular hyperkeratosis
Growth and development
• Retinoic acid is necessary for cellular
differentiation
• Retinoic acid triggers specific nuclear
receptors in the DNA for differentiation
• Important
Food Sources
• Preformed
• Liver, fish oils, fortified
milk, eggs
• half of vitamin A intake
• Proformed
• Dark leafy green, yellow,
orange veggies; also half
of vitamin A intake
Retinol Activity Equivalents
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1 RAE =
1 ug retinol
12 ug beta corotene
24 ug of other vitamin A
Precursor carotenoids
IU of vitamin A
• 0.3 ug retinol
• 3.6 ug beta carotene
• 7.2 ug of other vitamin A
precursors
RDA for vitamin A
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1000 RE for men
800 RE for women
Average intake meets RDA
No separate RDA for caroteniods
Vitamin A deficiency
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Less than 500 ugms per day
Growth failure
Infectious disease (diarrhea, measels)
Night blindness
Xeropthalmia
keratinization
Toxicity
• Results from long term supplement use (3-10 X
RDA or 15,000 ug RE)
• Large intake of vitamin A over long period of time
• bone./muscle pain, loss of appetite, skin disorders,
headache, dry skin, hair loss
• Discontinue supplementation, possible permanent
damage
• Hypercarotenemia from caroteinoids
Vitamin D
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Prohormone
Derived from cholesterol
Synthesis from sun exposure
Insufficient sun exposure makes this an
essential nutrient
• Activated by enzymes in the liver
• Deficiency can cause disease; rickets or
osteomalacia
Functions of Vitamin D
• Calcitrol influences differentiation of cells
• Increased protein synthesis
• Stimulates calcium binding protein in the
intestine
• Enhances calcium absorption in the
intestine
Vitamin D role in bone formation
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Decreases calcium excretion in the kidney
Causes Ca and Phos to deposit in the bones
Strengthens bones
Mobilizes calcium from bones depending
on blood calcium level
Food sources
• Fatty fish such as salmon and herring
• Fortified milk
• Other fortified foods
Adequate intake of vitamin D
• 5 ug/day (200 IU) for adults
• 10-15 ug/day (400-500 IU) for over age 51
• Casual sun exposure usually produces
enough vitamin D
• Infants are born with sufficient D to last 9
months
Toxicity of vitamin D
• Regular intake of 5-10 x the AI can be toxic
• Results from excessive supplementation and
not from sun exposure or milk consumption
• Overabsorption of calcium (hypercalcemia)
and increased calcium excretion
Vitamin E
• Tocopherols and tocotrienols
• Tansported via chylomicrons
• Found concentrated in areas where fat is
found
Antioxidant or redux agent
• Vitamin E is able to donate electron to
oxidizing agent
• Protects the cells from attack by free
radicals
production is normal result of cell
metabolism
destructive to cell membrane
Functions of vitamin E
• Protects the double bonds in fat
• Role in iron metabolism
• Maintenance of nervous tissue and
immune function
Food sources of vitamin E
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Plant oils and margarines
Wheat germ
Asparagus
Dark green leafy vegetables
Nuts and seeds
RDA for vitamin E
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8 mg/day for women
10 mg/day for men
Average intake meets RDA
1 mg vitamin E = 1.5 IU (from food source)
= 1.0 IU (from synthetic source)
Deficiency
• Red blood cell fragility
• Neurological disorders affecting the spinal
cord
• Anti aging vitamin?
Toxicity of vitamin E
• Supplements up to 800 IU is probably
harmless
• TUL is 1 gm/day
• Inhibits vitamin K metabolism and
anticoagulants
Vitamin K
• Phylloquinones and menaquinones
are active forms
• Role in the coagulation process
• Calcium binding potential
• Formation of osteocalcin
ood sources of vitamin K
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Liver
Green leafy vegetables
Broccoli
Peas
Green beans
Resistant to cooking losses
Limited vitamin K stores in the body
Drug Interactions
• Anticoagluant
Lessen blood clotting process
Need to monitor vitamin K intake
• Antibiotics
destroy intestinal bacteria
inhibits vitamin K synthesis and absorption
potential for excessive bleeding
RDA for vitamin K
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60-65 mg/day for women
65-80 mg/day for men
RDA is met by most people
Excess vitamin A and E interfere with K
Newborns are injected with vitamin K
Toxicity unlikely; readily excreted
Deficiency leads to bleeding/ hemmorhage