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Flashcards in Fat Soluble Vitamins Deck (43)
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Vit D - Metabolism

a. Absorption – chylomicrons
i. Requires fat absorption

b. Hydroxylation: First hydroxylation happens in the liver, the 2nd hydroxylation happens in the Kidney (then active)
i. D2 or D3 +OH in liver
-25 OH Vit D –level reflects body stores
ii. 25 OH Vit D hydroxylated in kidney to active form 1,25 OH Vit D (Calcitriol)


Vit D - Deficiency

a. Definition IOM Standard:
i. Deficiency 25OH Vit D <20 ng/mL
-Laboratory Specific alternate cutoffs may be inconsistent
Insufficiency 20-30 ng/mL
Sufficient >30 ng/mL

b. Classical Syndrome
i. Childhood rickets -


Emerging Associations with Vit D insufficiency or deficiency:

a. Mostly epidemiologic / in vitro

b. Few RCT’s to prove causation / treatment effect – stay tuned
i. Autoimmune Disorders (e.g. MS)
ii. Neuromuscular function
iii. Cardiovascular Disease
iv. Cancer incidence
v. Overall Mortality

c. IOM report Nov 2010 did not find adequate evidence (1100+pages)


Vit D – Risk for Deficiency

a. Low Sun exposure (NE winter)
i. Dark Pigmentation

b. Low dietary intake

c. Fat Malabsorption

d. Breastfed Infant supplement

e. Obesity
i. Fat sequestration, sedentary

f. Liver or Renal Disease (X-OH)
i. Need Calcitriol Rx supplementation


Vit D - Supplementation

a. Breastfed Infants
i. 400IU D3 per day by 2 months
ii. Until 500ml/d (>16oz) formula or milk
-Or formula fed taking <500ml/day

b. Children: AAP recs 400IU/d
i. IOM: E.A.R 400IU, RDA 600 IU/d for children
ii. 5-15 min sun (pigment)
-Dermatologist Academy and IOM prefer oral

c. Adults – recommendations vary
i. Institute of Medicine 600IU per day 18-70yrs
-800IU/day >70 years
-Some experts have recommended higher dosing 800-1000IU per day
-To Maintain 25OH D >30ng/mL, but evidence lacking


Vit D - Toxicity

a. Findings
i. Hypercalcemia
ii. Vomiting, seizures, nephrocalcinosis, vascular and soft tissue calcinosis

b. Risk
i. Sarcoidosis (granulomas activate D)
ii. >10,000 IU/d for wks in child or during pregnancy
iii. 50-100,000 IU daily in adult >3wks


Vitamin E – Function & Sources

a. Function: antioxidant, scavenges free radicals, stabilizes cell membranes

b. Sources: Polyunsaturated fat rich vegetable oils (e.g. sunflower), corn, nuts, wheat germ


Vit E – Deficiency

a. Neurologic Degeneration IRREVERSIBLE
i. Loss of reflexes (DTRs)
ii. Loss of coordination
iii. Loss of vibration and position sense
iv. Spinocerebellar ataxia
v. Neuropathy
vi. Ophthalmoplegia

b. Hemolytic Anemia

c. Risk:
i. malnurishment
ii. prematurity
iii. fat malbsorption / short gut


Vit E – Toxicity

a. Relatively Low

b. Coagulopathy
i. Very large doses inhibit Vit K dependent clotting factors

c. Literature does not support megadoses for CVD/cancer protection


Vit K – Function and Sources

a. Function – carboxylation of clotting factor proteins (II prothrombin, VII, IX, X)

b. Sources – leafy greens, brocolli, fruits, seeds, beef liver
i. Synthesis by Intestinal Bacteria


Vitamin K - Deficiency

a. Findings:
i. prolonged coagulation time
ii. Hemorrhagic disease of the newborn
-Purpura, GI bleeds, CNS bleeds

b. Risk:
i. Newborns – poor placental transport
-2-12 wks breastfed untreated
ii. Fat Malabsorption
iii. Chronic Antibiotics

c. Prevention:
i. all Newborns 0.5-1.0mg IM once
ii. Adequate oral dosing has not been defined


Summary of Deficiency Findings

Vitamin A
i. Finding: Eyes, epithelium, infections
ii. Risk for def: Poor or extreme low fat diet

Vitamin D
i. Finding:Rickets, Osteopenia/malacia, possibly more?
ii. Risk for def: Low sun, dark pigment, obesity, breastfeeding, liver/kidney dz

Vitamin E
i. Finding: Neurologic, anemia
ii. Risk for def: prematurity

Vitamin K
i. Finding: Impaired clotting
ii. Risk for def: Newborn, antibiotics, poor diet


Vitamin D Deficiency

Definition IOM Standard:
i. Deficiency 25 OH Vit D <20 ng/mL
-Laboratory Specific alternate cutoffs may be inconsistent
ii. IOM
-Insufficiency 20-30 ng/mL
-Sufficient >30 ng/mL

b. Classical Syndrome
1. Childhood rickets -failure of calcification, wide metaphyses: wrists, ‘rosary’, bone pain, bowed legs, fractures

2. Adult Osteoperosis