fat soluble vitamin Flashcards
Fat soluble vitamins
ADEK
Preformed
*Retinoids (retinal, retinol, retinoic acid)
*Found in animal products
*Provitamin A
*Carotenoids
*Must be converted to retinoid form
*Found in plant products
carotenoids to retinoids
*Enzymatic conversion of carotenoids occurs in liver or intestinal cells, forming retinal
and retinoic acid
Provitamin A carotenoids
*Beta-carotene
*Alpha carotene
*Beta-cryptoxanthin
Retinoic acid is required for structural
components of eye
*Cones in the retina: *Responsible for vision under bright lights& *Translate objects to color vision
*Rods in the retina: *Responsible for vision in dim lights & *Translate objects to black and white vision
Retinoic acid
cellular differentiation, Embryo development, gene expression
Retinoic acid influences
production, structure, and function of epithelial cells that line the outside (skin) and external passages (mucus forming cells) within the body
vitamin A deficiency
leads to decreased resistance to infections
Sources of Vitamin A
*Dark leafy green, yellow-orange
vegetables/fruits
absorption of vitamin a: carotenoids
*Absorbed intact, absorption rate much lower
*Intestinal cells can convert carotenoids to retinoid
absorption of vitamin a: retinoids
Retinyl esters broken down to free retinol in small intestine - requires bile, digestive enzymes, integration into micelles
transport and storage of vitamin a
*Liver stores 90% of vitamin A in the body
*Reserve is adequate for several months
*Transported via chylomicrons from intestinal
cells to the liver
*Transported from the liver to target tissue as
retinol via retinol-binding protein, which is
bound to transthyretin
excretion of vitamin A
*Not readily excreted
*Some lost in urine
*Kidney disease and aging increase risk of
toxicity because excretion is impaired
toxicity of vitamin a
*GI effects
*Headaches
*Blurred vision
*Poor muscle coordination
Hypervitaminosis A
results from long-term supplement use (2 – 4 x RDA
vitamin a deficiencies
*Xerophthalmia
*Night blindness
*Follicular hyperkeratosis
Teratogenic (may occur with as little as 3 x RDA
of preformed vitamin A)
*Tends to produce physical defect on
developing fetus
*Spontaneous abortion
*Birth defects
classification of vitamin D
Vitamin D3 (Cholecalciferol) & Vitamin D2 (Ergocalciferol)
Ergocalciferol (D2)
is synthesized in plant and fungi when ergosterol undergoes photolysis under UV light
Cholecalciferol (D3)
is synthesized in skin of animals by photolysis of 7-dehydrocholesterol
Bioactivation occurs through 2 steps
- Hydroxylation in liver produces calcidiol
- Hydroxylation in kidney produces calcitriol
Functions of vitamin d
i. Maintains structural integrity of bones & bone growth by regulating use of calcium + phosphate (bone turnover) (Calcitriol)
ii. Maintains serum Ca and P homeostasis
iii. Play a role in immune function and protection from chronic diseases
Vitamin D sources
Fortified foods (milk and orange juice)
* Fish liver oil = Cod liver oil contains over 1000IU/tablespoon
* Fatty fish (salmon, tuna)
* Liver, beef
* Sunlight exposure = 5-30 minutes in direct sunlight at mid-day
* Supplements
avsorption, transprot and storage
Absorptive cells: incorporated
into chylomicrons – Enter lymphatic systems – Enter plasma by transcalciferin – Stored in the liver (little)
toxicity
only occurs when you take more than 40 000IU of vitamin D per day over a long period of time
Effects of Vitamin D Toxicity
- Loss of appetite
- weight loss
- anorexia
- muscle fatigue and weakness
- vomiting
- cramping
- constipation
- frequent thirst and urination
rickets
*Softening of bones due to insufficient vitamin D
*Sufficient collagen, lack calcium
*Cause bow and fractures
Vit E: Classification
tocopherol, Tocotrienol
Absorption of vit e
Absorbed in the upper small intestine by
micelle-dependent diffusion
Storage of vit e
membranes and adipose tissues
excretion
feces and urine
functions of vit e
Antioxidant in the cell
how vit e is antioxidant in the cell
Prevent oxidative degradation by ROS
Protects PUFAs
How: As a membrane free radical scavenger (donate H atom)
Involving SOD, GPX and catalase (enzyme)
Reduce oxidative stress
Functions of vit e other than antioxidant
Inhibits platelets aggregation (clot)
Enhances vasodilation
Toxicity of vit e
Decrease the body’s ability to use other
fat-soluble vitamins
Impaired blood clotting
deficiencies of vit e
Loss of muscle coordination, vision, immune functions
Hemolytic anemia in children
Premature infants
Male infertility (animal study)
Vit K: Classification
Vitamin K1 (Philloquinones) / Vitamin K2 (Menaquinones) / Vitamin K3 (Meadione)
Absorption, Transportation and storage of k1
By an energy-dependent process in the small
intestine
Absorption, Transportation and storage of k2 and k2
By passive diffusion in the small
intestine
Functions of vit k
Aids in blood clotting
absorption
Incorporated into chylomicrons in the lymph
, then into liver , into VLDL and into peripheral tissues
how vit k Aids in blood clotting
Initiates the healing process by slowing and stopping the bleeding
Given to patients before surgery to prevent excessive bleeding
Vitamin K is the coenzyme to Vitamin K-dependent coagulation proteins in the blood coagulation cascade known as factors II, VII, IX, and X
how vit k Aids in Ca absorption
Aids in the prevention and treatment of osteoporosis and the loss of bone density
Vitamin K activates a protein called osteo-calcin which is responsible for building and maintaining strong bone tissue
Vitamin K’s role is enhanced when taken with Vitamin D and magnesium which helps maintain healthy bones
sources of vit k
Dark green vege, dairy products, meat, eggs, fruits and cereals
Deficiencies of vit k
Hemorrhage (bleeding from ruptured blood vessels)
Heavy menstrual bleeding
Hip fractures
