Chapter 13: Vitamin D

Question 1

Vitamin D

Answer 1

considered a hormone, synthesized at one location and acts in another location, can be synthesized through exposure to sunlight

Question 2

functions of vit D

Answer 2

required for calcium and phosphorus absorption in the small intestine, regulates blood calcium levels, works with PTH to stimulate osteoclasts and necessary for bone calcification, linked to immune system, reproduction, and gene activity all needing more research

Question 3

Vit D synthesis in the skin

Answer 3

7 dehydrocholesterol (precursor made in the liver from cholesterol) and UV light form previtamin D3, added heat from the body causes the formation of Vit D3(calcicole)

Question 4

Vit D synthesis from the diet

Answer 4

consume vit D2 from plants and v3 from animals

Question 5

Vit D activation

Answer 5

in the liver it goes through hydroxylation in the liver to form calcidiol, and then goes through hydroxylation in the kidneys to form calcitriol

Question 6

Vit D DRI

Answer 6

Assumes no synythesis from the sun

Question 7

Vit D RDA

Answer 7

values range from 15-20 ug/day, higher amounts in older adults due to decrease capacity to synthesize vitamin D , it also assumes the persons sun exposure is inadequate

Question 8

Sources of Vitamin D

Answer 8

Ergocalciferol (D2)- plants, supplements
Cholecalciferol (D3)- animal foods, sun
most food naturally contain little vitamin, mostly obtained from fortified foods (milk)

Question 9

Too high of Vit D consumption

Answer 9

can occur from vitamins, fish oil supplements, results in hypercalcimia (high blood calcium)

Question 10

Not enough vit D

Answer 10

can occur with disease that reduce intestinal absorption of fat, rickets occuring in children and osteomalacia in older adults