vitamin d

1922

hone was vitamin d discovered?

calciferol

what is another name for vitamin d?

ergocalciferol, cholecalciferol

the plant form of vitamin d is called _________ (D2) and the animal form is _________ (D3).

7-dehydro-cholesterol

vitamin d can be made in the skin because __________, a derivative of cholesterol, is found int he skin and can be activated into cholecalciferol.

7-dehydro-cholesterol is activated into cholecalciferol; D3 travels through the bloodstream to the liver where it is converted into 25-OH vitamin d (Calcidiol); this travels to the kidneys where 1,25 dihydroxyl vitamin d (calcitriol) is made.

explain how the skin and UV can make vitamin d in the body.

calcidiol

25-OH vitamin d; 5x ac active as cholecalciferol

calcitriol

1,25 dihydroxy vitamin d; 10x as active as cholecaliferol

fatty fish, fish oils, fortified foods

what are the best sources of vitamin d?

milk, orange juice, yogurt, breads, cereals, infant formulas

what are some of the foods fortified with vitamin d?

15-30, 100

___-____ min of sunlight exposure can produce about _________x more vitamin d that a serving of fortified milk.

5-10, 5

___-____ minutes if arms/legs exposed can generate _____x the RDA for vitamin d.

33rd

those living north of the ______ parallel are more likely to be vitamin d deficient.

darker skin tones have lower synthesis; 6x longer exposure; melanin blocks UVB rays

how does skin tone impact vitamin d?

not same; skin cancers, wrinkles

how do tanning beds impact vitamin d?

skin tone, day season, latitude, altitude, cloud cover, sunscreen, age, air pollution/smog

what factors influence skin production of vitamin d?

50

it is estimated that ____% of dietary vitamin d is absorbed by passive diffusion into intestinal cells.

1,25 diOH vitamin d (calcitriol)

what is the active form of vitamin d?

25-hydroxylase

the liver forms 25-OH vitamin D by way of the _________ enzyme.

1, 25 -hydroxylase

the kidneys from 1,25 dish vitamin d by way of the _______ enzyme.

calcium homeostasis, cell differentiation, immune function, reducing inflammation, muscle structure and function

what are some of the functions of vitamin d?

when blood calcium falls, PTH is released from the PT gland. the rise in PTH acts on the kidneys and increases the activity of 1,25 hydroxylase which increases the amount of calcitriol produced.

how does PTH and vitamin d impact calcium homeostasis?

stimulates reabsorption of calcium in the kidneys so less is excreted; promotes active, energy-requiring absorption of calcium through stimulation of Ca binding protein in the gut expressed on the brush border.

what are the effects of elevated calcitriol when blood calcium is down?

PTH released, increasing vitamin d activity

what happens when blood calcium falls?

calcitonin releases, inhibits vitamin d activity

what happens when blood calcium rises?

non-genomic and genomic

how does vitamin d all of these things?

non-genomic

calcitriol binds a cell membrane receptor and induces an intracellular cell signaling cascade. this causes a pretty quick cellular response which may facilitate any of he functions.

genomic

calcitriol enters the cell, moves through the cytosol, and enters the nucleus. once in the nucleus, calcitriol binds to VDR, becoming active TF. calcitriol-VDR complex can then bind DNA directly on specific DNA sequences. binding influence the contraction or expansion of chromatin allowing transcription to be activated or repressed.

200

it is estimated that at least ______ genes have DNA binding sites for calcitirol-VDR.

600, 15

the vitamin d RDA for everyone over 1 yo is _________ IU/day or ______ mg/day.

800, 20

the vitamin d RDA after the age of 70 is ________ IU or ______ mg/day.

40, 0.025

1 microgram = ______ IU; 1 IU = _______ micrograms vitamin d.

calcium deposits, poor growth, muscle weakness, mental confusion

what are the symptoms of vitamin d toxicity?

rickets

malformation of bone in children; bowed legs, pigeon chest; linked to breast milk not being a good source of vitamin d

osteomalacia

softening of bones because of decreased mineral deposition; bent spine, bowed legs, waddling gait, facial twitching; older adults and women at greatest risk, also women who wear religious coverings

nutrigenomics

vitamin d binding to a TF and regulating gene expression is an example of _________.