Fat Soluble Vitamins

Question 1

Functions and source of Vitamin A

Answer 1

Essential for retinal signaling, maintenance of conjunctival membranes, and cornea; some function in immune regulation

Sources: Pre-formed Vitamin A (retinol) in liver, dairy, egg yolks, fish oil

Precursors (beta carotene) in carrots, spinach, broccoli, pumpkin

Question 2

Vitamin A Deficiency

Answer 2

Night blindness
Xeropthalmia (corneal dryness)
Bitot’s spots - white, keratinized spots on the conjunctival membrane
Immune deficiency - especially in children

Question 3

Vitamin A Toxicity

Answer 3

Only with pre-formed retinol (not beta carotene precursors)

Increased intracranial pressure, vomiting, headache
Bone pain, fractures, osteoporosis
Liver damage
Birth defects

Question 4

Vitamin D Function

Answer 4

Maintains intracellular & extracellular [Ca2+] by

stimulating absorption of Ca2+ and P from the intestine, mobilization from bone, and renal reabsorption

Question 5

Vitamin D Metabolism

Answer 5

Dehydrocholesterol in skin is converted to cholecalciferol (D3) by UV light

D3 from the skin enters circulation and travels to the liver, where it is hydroxylated to 25-OH-D; 25-OH-D travels to the kidney where it is hyroxylated to 1,25-(OH)-D (i.e. calcitriol - this is the active form)

Question 6

Vitamin D Deficiency

Answer 6

Childhood Rickets - failure of cartilage calcification; presents with bowed legs, widened metaphyses (wrists), bone pain, fractures, ‘rachitic rosary’

Adult osteoporosis

Risk: Lack of sunshine exposure, low dietary intake, fat malabsorption, dark skin, obesity, liver or renal disease

Question 7

Evaluation of Vitamin D Levels

Answer 7

Serum 25(OH) reflects body stores
Decreased serum Ca2+ and P
Elevated Alk Phos
Elevated PTH

Question 8

Sources of Vitamin D

Answer 8

D3 from animal sources - fish oil, egg yolk, fortified milk

D2 from plant sources (algae)

Question 9

Vitamin E Function and Sources

Answer 9

Anti-oxidant, cell membrane stabilizer

Sources: Vegetable oils, wheat germ

Question 10

Vitamin E Deficiency

Answer 10

Irreversible neurologic degeneration - decreased DTRs, ataxia, neuropathy, opthalmoplegia, loss of position / vibration sense

Hemolytic anemia

Question 11

Vitamin E Toxicity

Answer 11

Coagulopathy - very large doses inhibit Vitamin K dependent factors

(Rare)

Question 12

Vitamin D Toxicity

Answer 12

Hypercalcemia - nephrocalcinosis, vascular and soft tissue calcinosis

Seizures

Question 13

Vitamin K function and sources

Answer 13

Essential for carboxylation of coagulation proteins - Factors II, VII, IX, X

Sources: Leafy vegetables, fruits, seeds; synthesized by intestinal bacteria

Question 14

Vitamin K Deficiency

Answer 14

Prolonged coagulation time; hemorrhagic bleeding into skin (purpura), GI tract, CNS

Risk increased in newborns due to poor placental transport and sterile gut; risk also increased with chronic antibiotic use

Question 15

Vitamin D supplementation recommendations

Answer 15

400 IU/day to all breastfed infants until receiving 500ml/day of fortified formula or milk

Question 16

Vitamin K supplementation recommendations

Answer 16

All newborns should receive a one time IM dose (0.5 - 1.0 mg)