Fat Soluble Vitamins Flashcards
Vitamins:
a. Complex organic substances required in small quantities in the diet relative to all other nutrients except the trace elements; “essential” because substance can’t be synthesized at all or in adequate quantities to meet metabolic needs.
b. Vitamins have precise, specific functions in metabolism and thus help maintain normal functions of all organs.
Water and Fat Soluble Vitamins
a. Water soluble:
- generally not stored (except Vitamin B-12), but chronic intake affects tissue levels
- highly absorbed from dietary sources
- excreted via urine
- low toxicity.
b. Fat soluble:
- accumulated “stores” in body;
- require absorption of dietary fat and a carrier system for transport in blood
- potential for toxicity with excessive inatke.
Fat soluble Vitamins:
a. accumulated “stores” in body;
b. require absorption of dietary fat and a carrier system for transport in blood
c. potential for toxicity with excessive intake.
The Fat Soluble Vitamins: Vit A Vit D Vit E Vit K
Vitamin A Summary
VITAMIN A
a. Function: essential in photochemical basis of vision (signals in retina–>brain visual cortex); maintenance of conjunctival membranes & cornea; critical for epithelial cellular differentiation and proliferation
b. Food sources:
i. preformed Vit A (retinol/retinal): liver, dairy products, egg yolks, fish oil (e.g. cod liver oil)
ii. precursor (carotenoids e.g. beta-carotene): abundant in deep yellow/orange & green vegetables, eg. spinach, carrots, broccoli, pumpkin
c. Deficiency:
•Night blindness, xerophthalmia (extreme dryness of cornea), Bitot’s spots on sclera, eventual blindness;
• Immune deficiency – dysregulation of immune response; effect depends on infectious agent & type of immune response it elicits; supplementation to correct Vit A deficiency ↓’s child mortality by 23-34%
• Abnormal epithelial morphology: epithelial, linings become flattened, dry & keratinized
• Vit A treatment of infants & children with measles associated w/ reduced morbidity & mortality; data strongest in developing countries; supportive data in U.S. children w/ low retinol levels;
d. Risk of deficiency: low intake &/or low fat intake (fat < 5% of kcal); fat malabsorption (liver disease & low bile salts; pancreatic insufficiency); protein energy malnutrition
Vitamin A Deficiency
- Night blindness, xerophthalmia (extreme dryness of cornea),
- Immune deficiency – dysregulation of immune response; effect depends on infectious agent & type of immune response it elicits; supplementation to correct Vit A deficiency ↓’s child mortality by 23-34%
- Abnormal epithelial morphology: epithelial, linings become flattened, dry & keratinized
- Vit A treatment of infants & children with measles associated w/ reduced morbidity & mortality; data strongest in developing countries; supportive data in U.S. children w/ low retinol levels;
Vitamin A function and food sources
a. Function: essential in photochemical basis of vision (signals in retina–>brain visual cortex); maintenance of conjunctival membranes & cornea; critical for epithelial cellular differentiation and proliferation
b. Food sources:
- Preformed Vit A (retinol/retinal):
i. liver, dairy products, egg yolks, fish oil (e.g. cod liver oil) - Precursor (carotenoids e.g. beta-carotene):
i. abundant in deep yellow/orange & green vegetables, eg. spinach, carrots, broccoli, pumpkin
Toxicity and Biochemical Evaluation of Vitamin A
a. Toxicity (only w/ preformed Vit A retinol, dose dependent): vomiting, increased intracranial pressure, headache, bone pain (periosteal proliferation), bone mineral loss (↑ fractures & ↑ osteoporosis), liver damage (hepatitis, fibrosis, liver failure), death; birth defects
b. Biochemical evaluation: serum retinol (but levels remain WNL until liver stores nearly exhausted & ↓ w/ Acute Phase Reaction)
Vitamin D
Huge Summary
VITAMIN D
a. Function: functions as a hormone; maintains intracellular & extracellular Ca++ w/in physiologic range; stimulates intestinal absorption Ca++and P, renal reabsorption of Ca++ and P, mobilization of Ca++ and P from bone; innate immune function (generation of toxic radicals), cellular growth and differentiation through nuclear and plasma membrane vitamin D receptors present in many types of cells, other: active area of scientific inquiry…
b. Sources:
i. precursor (dehydrocholesterol) in skin, converted to cholecalciferol (Vit D3) by UV light;
ii. Dietary sources: a) Natural: fish liver oils, fatty fish, egg yolks; b) fortified milk & formulas D3 from animal sources, D2 ergocalciferol from plant (algae) sources; D3 activity 2-3x > D2
c. Metabolism:Absorbed via chylomicrons; Vitamin D2 or D3 hydroxylated in liver, to 25-hydroxy-cholecalciferol and then in kidney to 1,25-dihydroxy-cholecalciferol (calcitriol) = active form
Deficiency:
d. Deficient:
i. 25OH-D <20 ng/mL (<50nmol/L) Insufficient: 21-29 ng/mL (50-80 nmol/L) Sufficient: >/= 30 ng/mL (>80 nmol/L) evidence building of association of sufficiency with decreased risk chronic illnesses
ii. Rickets: (25OH-D <11ng/mL) failure of maturation of cartilage and calcification; “rachitic rosary” on ribs, bowed legs, widened metaphyses (esp at wrist), painful bones, fractures;
iii. decreased serum Ca and P, increased alk phos (+ classic triad = late findings); decreased 25(OH)Vit D & increased PTH
iv. Vit D insufficiency “New epidemic”? - Increased rates of low 25(OH)D levels - Increased indoor time, sunscreen use;
v, NHANES 42% African American women of child bearing age <15ng/mL
e. Rapidly evolving ecologic/ epidemiologic/in vitro/RCT evidence links to autoimmune diseases, neuromuscular function, heart disease, cancer incidence, and even overall mortality. Nov 2010 Institute of Medicine Report found only reliable evidence for bone health. Stay tuned as evidence base evolves.
f. Risk of deficiency: lack of adequate sunshine exposure; low dietary intake; fat malabsorption (cystic fibrosis, liver disease, prox. sm. intest disease, orlistat – intestinal lipase inhibitor); breastfed infant, esp if mother deficient (low infant stores at birth); dark skin (increasedpigmentation=decreased skin conversion; difficult to quantify); obesity (sequestered in fat); liver or renal disease (unable to activate – need calcitriol). Much recent data/discussion re whether U.S. population levels «_space;optimal, esp in northern latitudes; also elderly, w/ outdoor exposure & conversion.
Recommendation for Vitamin D
Recommendation:
Supplement (400 IU D3) to all breastfed infants until receiving at least 500 ml(16oz+)/day infant formula or milk; non-breastfed infants/children not receiving > 500 ml infant formula or Vit D fortified milk.
Other: 5-15 min unprotected sun exposure or UVB tanning (varies with pigmentation) x 2-3x/wk not recommended by American Academy of Dermatology
Vitamin D Function and Sources
a. Function: functions as a hormone
i. maintains intracellular & extracellular Ca++ w/in physiologic range
ii. stimulates intestinal absorption Ca++and P, renal reabsorption of Ca++ and P
iii. mobilization of Ca++ and P from bone
iv. innate immune function (generation of toxic radicals)
v. cellular growth and differentiation through nuclear and plasma membrane vitamin D receptors present in many types of cells
b. Sources:
i. precursor (dehydrocholesterol) in skin, converted to cholecalciferol (Vit D3) by UV light;
ii. Dietary sources:
a) Natural: fish liver oils, fatty fish, egg yolks;
b) fortified milk & formulas D3 from animal sources, D2 ergocalciferol from plant (algae) sources; D3 activity 2-3x > D2
Vitamin D Deficiency Large Summary
Deficient:
1) 25OH-D <20 ng/mL (<50nmol/L) Insufficient: 21-29 ng/mL (50-80 nmol/L) Sufficient: >/= 30 ng/mL (>80 nmol/L)
- evidence building of association of sufficiency with decreased risk chronic illnesses
2) Rickets: (25OH-D <11ng/mL) failure of maturation of cartilage and calcification; “rachitic rosary” on ribs, bowed legs, widened metaphyses (esp at wrist), painful bones, fractures;
3) decreased serum Ca and P, increased alk phos (+ classic triad = late findings); decreased 25(OH)Vit D & increased PTH
4) Vit D insufficiency “New epidemic”? - Increased rates of low 25(OH)D levels - Increased indoor time, sunscreen use;
5) NHANES 42% African American women of child bearing age <15ng/mL
VITAMIN E
Summary
a. Function: antioxidant, free radical scavenger; cell membrane stabilizer
b. Food sources: polyunsaturated vegetable oils, wheat germ
c. Deficiency: neurologic degeneration: with loss of reflexes (DTR’s), spinocerebellar ataxia, neuropathy, ophthalmoplegia; incoordination, loss of vibration and position sense; hemolytic anemia
d. Situations with risk of deficiency: prematurity, fat malabsorption syndromes, short gut syndrome, C.F.
e. Toxicity: low; coagulopathy (very large doses inhibit Vit K dependent factors);
i. Megadoses for protection against heart disease and/or cancer not supported by most current literature (see refs)
Vitamin E Deficiency
Deficiency: Neurologic Degeneration:
i. with loss of reflexes (DTR’s),
ii. spinocerebellar ataxia
iii. neuropathy
iv. ophthalmoplegia
v. incoordination, loss of vibration and position sense; hemolytic anemia
d. Situations with risk of deficiency: prematurity, fat malabsorption syndromes
VITAMIN K
Summary
a. Function: essential for carboxylation of coagulation proteins (Factors II (prothrombin), VII, IX, X)
b. Sources: leafy vegetables, fruits, seeds; synthesized by intestinal bacteria
c. Deficiency: prolonged coagulation times; hemorrhagic disease of newborn: bleeding into skin (purpura), gi tract, CNS
d. Risk of deficiency: newborns (poor placental transport, sterile gut, low clotting factors); late (2-12 wk), esp. breastfed infants (breast milk relatively low) or fat malabsorption syndromes, chronic antibiotic use.
e. Recommendation: All newborns should receive single IM dose of 0.5-1.0 mg (adequacy of oral doses presently not defined)
Function and Deficiency of Vitamin K
Function: essential for carboxylation of coagulation proteins (Factors II (prothrombin), VII, IX, X)
Deficiency: prolonged coagulation times; hemorrhagic disease of newborn: bleeding into skin (purpura), gi tract, CNS
Vitamin Definition
a. Complex organic substances required in small quantities in the diet relative to all other nutrients except the trace elements; “essential” because substance can’t be synthesized at all or in adequate quantities to meet metabolic needs.
i. Our body cannot make vitamins!
b. Vitamins have precise, specific functions in metabolism and thus help maintain normal functions of all organs.
Water vs Fat Soluble Vitamins
There is more possibility of fat soluble vitamin toxicity due to storing in body
a. Water soluble:
i. generally not stored (except Vitamin B-12 in the muscle), but chronic intake affects tissue levels
ii. highly absorbed from dietary sources;
iii. excreted via urine;
iv. low toxicity.
b. Fat soluble:
i. accumulated “stores” in body
ii. require absorption of dietary fat and a carrier system for transport in blood
- need a carrier in blood due to hydrophobic nature
iii. potential for toxicity with excessive intake.
