Vitamin D Flashcards
What is the plant form of vitamin D called?
Cholecalciferol (Vitamin D3)
What is the animal form of vitamin D called?
Ergocalciferol (Vitamin D2)
What is the time frame and frequency for vitamin D synthesis?
5-10 min between 10AM -3PM. 2-3x/week
When intake of vitamin D3 happens via food how is it absorbed and digested?
50% absorbed by passive diffusion in the SI
Where in the SI is vitamin D3 mostly absorbed?
Ileum
After absorption, where does vitamin D go and how does it get there?
Goes to liver.
60% packed into chylomicrons -> Liver
40% bound to vitamin D binding protein (DBP) -> Liver
How does vitamin D that is taken in by the skin get to the liver?
Bound to DBP
What form is Vitamin D3 in the liver? What is its half life?
Calcidiol: 25-hydroxy vitamin D3 (Inactive) - 60 days half life
What form is Vitamin D3 in the kidneys? What is its half life?
Calcitriol: 1,25-hydroxy vitamin D3 (active) - 4 to 6 hour half life
Where is Vitamin D found in high concentrations?
Kidneys (limits amount of active calcitriol)
24 hydroxylase is found in all cells. What do mutations to this gene cause?
Hypercalcemia
T/F
All cells contain vitamin D receptors? Vitamin D is known to control >200 genes
True
How is vitamin D3, calcidiol and calcitriol transported to tissues from the blood?
Via DBPs
What minerals does vitamin D balance?
Calcium and phosphorus
Vitamin D functions in cell differentiation and growth. How does it affect cancer cells?
Prevents cancer cells from replicating.
Vitamin D plays a role in cell differentiation in regards to many systems. What are some examples?
Immune system, nervous system, prevention of CVD and MS, etc.
What does Vitamin D turn stem cell monocytes into?
Osteoclasts
How does Vitamin D affect gene expression ultimately?
By acting as a transcription factor for target genes
What does a severe vitamin D deficiency do to muscles?
Induces type II fiber degradation
How does vitamin D affect insulin sensitivity?
Aids in improving it
T/F
Vitamin D has a powerful antiinflammatory effect?
True, this may be why adequate vit D intake may decrease the production of solid tumors
What is the vitamin D level appropriate overall for adults?
For ages 1-70 technically 600 IUs, but at least 800 IUs seems to be most appropriate for adults.
What is the adequate vit D intake for infants (<1 year)?
400 IUs
What are poor sources of vitamin D?
Breast milk, unfortified dairy
A vitamin D deficiency (<20 ng/mL) is often misdiagnosed as what condition?
Fibromyalgia
What is the normal (minimum amount to prevent rickets) of vitamin D?
30-80 ng/mL
If serum levels of vit D are deficient, how much will it take to achieve normal levels?
1000 IU daily for 2 to 3 months
What clinical sign or symptom is associated with hyperkeratosis?
Xerophthalmia
What is the precursor for endogenously produced vitamin D?
Cholesterol
In what organ does the enzyme Alpha-1-hydroxylase hydroxylate vitamin D3 to its fully active form?
Kidney
Dietary vitamin D is transported via ________; while endogenous vit D is transported via _______
Chylomicrons; DBP
How does Vit D increase calcium absorption?
Induced synthesis of Ca++ binding protein
What does hypovitaminosis D do to bones?
Soft, spongy bones. Rickets(children) Osteomalacia (adults).
T/F
Low back pain is implicated in hypovitaminosis D
True
What kind of inflammatory conditions are associated with hypovitaminosis D?
RA, inflammatory bowel disease.
What kind of psychological conditions are associated with hypovitaminosis D?
Depression, alzheimer’s, schizophrenia, anxiety
What are some cardiovascular issues associated with hypovitaminosis D?
Hypertension, atherosclerosis, metabolic syndrome.
T/F
Diabetes can associated with hypovitaminosis D
True
T/F
Solid cancers can be associated with hypovitaminosis D
True
What are 3 major causes of hypovitaminosis D?
Reduced skin synthesis
Decreased bioavailability (malabs, obesity)
Other
What are some causes of vit D deficiency under the “other” category?
Breastfeeding
Liver/kidney failure
Phosphate depletion
What is the safe upper limit for vit D?
4,000 IU/day
What is toxic serum calcidiol?
> 150 ng/mL
T/F
There have been a few cases identified, of vit D toxicity due to excessive sunlight
False,
No cases
What are 3 conditions where Vit D supplementation is cautioned
- Hyperparathyroidism
- Granulomatous disorders (sarcoidosis, TB)
- Some lymphomas
