Vitamin D

Question 1

Vitamin D

Answer 1

• Calciferol
• Body can synthesize it with help of sunlight
• Two major forms

Question 2

Two major forms of vitamin D

Answer 2

1. Vitamin D2 (ergocalciferol): plant foods form
2. Vitamin D3 (cholecalciferol): animal foods form; form synthesized in human skin
   - Vitamin D’s metabolic conversions
   Requires conversions by the liver and kidneys

Question 3

Vitamin D’s metabolic conversions

Answer 3

• Liver manufactures precursor
• in skin, this compound converted to second precursor in the presence of ultraviolet rays
• requires additional conversions by the liver and the the kidneys to produce active vitamin (calcitriol)
• PTH increases the activity of the enzyme that produces active vitamin D
• the step necessary with dietary vitamin D as well

Question 4

Vitamin D’s roles in health

Answer 4

• although known as a vitamin, vitamin D is actually a hormone - a compound manufactured by one organ of the body that has effects on another.
• target organs: small intestine, kidneys, and the bones.

Question 5

Brain and nerve cells

Answer 5

• brain and nerve cells: vitamin D may protect against cognitive decline and may help to slow the progression of parkinson’s disease

Question 6

Muscle cells

Answer 6

vitamin D in muscle cells encourages muscle strength and function in children and preserves strength in adults

Question 7

Immune System

Answer 7

vitamin D signals cells of the immune system to defend against infectious diseases
- binds to receptors on B and T cells and antigen presenting cells stimulating their immune function

Question 8

Adipose tissue (obesity)

Answer 8

may regulate the cells of the adipose tissue in ways that might contribute to obesity. some research has shown an association between obesity, insulin resistance, and low vitamin D levels/

Question 9

a deficit in vitamin d may be associated with: Diseases

Answer 9

high blood pressure, type 2 diabetes, and some cancers, respiratory tract infections, inflammatory conditions, and dementia

Question 10

Vitamin D’s role in bone growth

Answer 10

• maintains bone health by assisting in calcium and phosphorus absorption
• regulates blood concentrations of bone minerals:
  Enhances their absorption from GI tract (when diet is sufficient)
  stimulates reabsorption from blood by the kidneys (when diet is insufficient)
  triggers mobilization from bones into blood (when diet is insufficient)

Question 11

Parathyroid Hormone

Answer 11

• a hormone released when body detects calcium levels in your blood are too low
• stimulates release of small amounts of calcium from the bones
• happens when there is too much phosphorus
• Kidneys: enables production of active vitamin D (calcitriol) in the kidneys
• PTH stimulates your small intestine to absorb more calcium from the food you eat

Question 12

Vitamin D deficiency

Answer 12

• contributing factors: dark skin, breastfeeding without supplementation, lack of sunlight, and not consuming fortified milk
• diseases: rickets: weakening of bones. Osteomalacia: softening of bones. Osteoporosis: reduced density of bones

Question 13

Vitamin D toxicity

Answer 13

• causes excess blood calcium, calcification

Question 14

Vitamin D from the Sun

Answer 14

• Can pose risk of skin cancer, but not vitamin D toxicity
• 5-10 minutes sun exposure (hands, face, arm) a few times a week in summer adequate for most (affected by skin colour, latitude, season, time of day)

Question 15

Vitamin D in foods and reccomendations

Answer 15

• Eggs, liver, butter, some fatty fish, and fortified milk
• supplements for breastfed infants
• DRI assume no skin synthesis
• Age increases risk of vitamin D deficiency because of skin changes, vitamin D synthesis is less efficient, impaired absorption, more time spent inside