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HUNT241 > Nutrition Lecture 6: Vitamin D > Flashcards

Nutrition Lecture 6: Vitamin D Flashcards

1
Q

What is the main source of Vitamin D?

A

The sun!!

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2
Q

What are some food sources of Vitamin D?

A

Cod liver oil, Sardines, Smoked salmon, Eel/tuna, some dairy

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3
Q

What is essential to make vitamin D?

A

Cholesterol is essential to make vitamin D, but we still need to be careful about having too much

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4
Q

What type of reaction is the action of creating Vitamin D from sunlight on the skin?

A

Non-enzymatic reaction

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5
Q

What is the precursor for Vitamin D?

A

7-dehydrocholesterol forms vitamin D3

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6
Q

What are the three different types of sunlight radiation?

A

UVC, UVB, UVA

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7
Q

What is UVC?

A

The shortest wavelength, absorbed by the atmospheric ozone

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8
Q

What is UVB?

A

Has the largest effect on the top layer of skin, causes redness/burning, SKIN CANCER

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9
Q

What is UVA?

A

The longest wavelength, reaches deep into the layers of skin, causes aging/wrinkling

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10
Q

Most sunlight that gets through is….

A

UVA

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11
Q

What radiation is of most use and most concern?

A

UVB

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12
Q

What behavioural factors affect Vit D status?

A

Clothing, sunscreen, time of day, time spent outdoors, supplements, diet

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13
Q

What does global dietary Vitamin D uptake?

A

The mandatory food fortification countries have good vitamin D intake levels (Canada, USA) - Most other countries are not over AI

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14
Q

What are host-related factors that affect Vit D status?

A

Skin colour, age, sex, BMI, genetic differences

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15
Q

What is melanin?

A

Melanin is a natural pigment responsible for the coloration of skin, hair, eyes.

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16
Q

Where is global skin colours the darkest?

A

In countries closest to the equator

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17
Q

Melanin is a natural protection of what?

A

The harmful effects of UV light

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18
Q

What is one of the negative effects of melanin?

A

Have to spend more time in the sun to get sufficient Vit D

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19
Q

What are environmental factors that affect Vit D status?

A

Season, latitude, altitude, clouds, pollution

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20
Q

How does latitude affect vitamin D?

A

As latitude increases (moving towards the poles), the angle of the sun’s rays becomes more oblique, and the intensity of UVB radiation decreases

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21
Q

What are the two major forms of Vitamin D?

A

D2 and D3

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22
Q

Where do we get D2 from?

A

Plant foods and fungi

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23
Q

Where do we get D3 from?

A

Animal foods

24
Q

What does D2 start out as?

A

Ergosterol

25
Q

How does ergosterol become D2?

A
  • Starts out as ergosterol
  • Beta ring is broken down by UVB light
  • This forms Pre D2, with a broken ring
  • Then with the addition of heat it dorms vitamin D2
26
Q

What does D3 start out as?

A

7-dehydrocholesterol

27
Q

How does 7-dehydrocholesterol become D3?

A
  • Beta ring is broken by UVB light
  • This forms Pre D3, with a broken ring
  • Then with the addition of heat it forms Vitamin D3
28
Q

What is the main differences in structure between D2 and D3?

A

Extra double bond and methyl group on D2

29
Q

Why is D3 more effective than D2?

A

D2 has lower affinity for the Vitamin D binding protein, therefore is cleared faster from circulation

30
Q

Both D2 and D3 are transported in the blood via what?

A

Vitamin D Binding Protein (DBP)

31
Q

What type of vitamin is Vitamin D?

A

Fat-soluble

32
Q

What does vitamin D require to be absorbed?

A

Fat

33
Q

Where is vitamin D absorbed?

A

In the upper small intestine

34
Q

How is vitamin D absorbed in the small intestine?

A

By non-saturable passive diffusion

35
Q

How is Vitamin D transported from the intestine to the liver?

A

by vitamin D binding globulin

36
Q

What facilitates the absorption of vitamin D?

A

Mixed micelles

37
Q

How do mixed micelles facilitate the absorption of vitamin D?

A

by solubilizing it in the watery environment of the small intestine, allowing for efficient uptake by intestinal cells.

38
Q

Where is vitamin D soluble?

A

In the hydrophobic core of mixed micelles

39
Q

Is vitamin D from food or skin biologically active?

A

NO - requires metabolic activation in the body

40
Q

How is vitamin D made biologically active?

A

Either forms (D3, D2) Needs to be transported to the liver and then the kidney

41
Q

What happens when Vitamin D3/D2 is transported to the liver?

A

D3/D2 is converted into 25(OH)D = calcidiol

42
Q

What is the name for 25(OH)D?

A

Calcidiol

43
Q

What is the biomarker of vitamin D status?

A

Calcidiol

44
Q

Is calcidiol the active form?

A

No, needs to be transported from the liver to the kidneys to be activated

45
Q

What happens when Calcidiol is transported to the kidneys?

A

Calcidiol is converted into 1,25(OH)2D = Calcitriol

46
Q

What is the name for 1,25(OH)2D?

A

Calcitriol

47
Q

Is calcitriol the active form?

A

Yes!

48
Q

What is the vitamin D status of NZ adults?

A

68% = Sufficient
27% = Insufficient
5% = Deficient

49
Q

What is vitamin D status by season?

A
  • Great levels in summer
  • Decreases as winter comes closer
  • Parts of spring still low but starting to improve
50
Q

What is vitamin D status by ethnicity?

A

Maori and pacific:
- Less likely to get sunburnt
- Less likely to be forming Vitamin D

51
Q

What is vitamin D status by age and sex?

A

Women are lower than men

Males tend to stay the same or get higher with age
Women tend to get lower with age

52
Q

What is vitamin D status by region? (North vs South)

A

Northern region has the lowest prevalence of vitamin D deficiency

53
Q

What are rickets?

A

inadequate mineralization of growing bones in children, resulting in soft, weak bones and skeletal deformities

54
Q

What is osteomalacia?

A

softening of the bones due to impaired mineralization of the bone matrix in adults

55
Q

What is osteoid?

A

The bone protein matrix (primarily collagen)

56
Q

Does excessive sun exposure cause vitamin D toxicity?

A

No, sustained heat on skin degrades pre-vitmain D3 and D2

HUNT241 (22 decks)

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