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Nutrition FNH 351 > Bone Health > Flashcards

Bone Health Flashcards

1
Q

Vitamin D’s active form is

A

Calcitriol = 1,25 (OH)2D

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2
Q

Form of Vitamin D from animals

A

Cholecalciferol

Vitamin D3

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3
Q

Form of vitamin D from plants

A

Ergocalciferol

Vitamin D2

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4
Q

Main circulating form of Vitamin D, and biomarker of status

A

Calcidiol

25 (OH)D

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5
Q

Food Sources of Vitamin D

A

Fatty Fish, Liver
Shiitake mushrooms
Fortified milk or orange juice

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6
Q

Digestion of Vit D. From diet

A

Non required

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7
Q

Absorption of Vitamin D

A

With fats- micelles, chylomicrons

Fat soluble

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8
Q

Synthesis of vitamin D

A

In skin with exposure to UV light. Influenced by skin exposure, color, age, time of day, season

Cannot get toxic levels of Vit D through sun

Makes another product that gets sloughed off with dead skin cells

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9
Q

Transport of vitamin D

A

Bound to vitamin D binding proteins (DBP)

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10
Q

Activation of Vitamin D

A

Liver: calciferol converted to 25(OH)D -main circulating form = calcidiol = 25-hydroxyD

Kidney: 25(OH)D converted to 1,25(OH2)D - active form

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11
Q

Functions of Vitamin D

A

Genomic and non-genomic
Calcium regulation
Cell differentiation + proliferation

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12
Q

Vitamin D’s role in Calcium homeostasis

A

Low calcium = PTH increases = activates Vitamin D.

Vit D + PTH= 1. Increase Ca absorption 2. Increase Ca reabsorption form kidney 3. Promote cellular resorption from bone

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13
Q

Vitamin D deficiency

A

In children- Rickets under mineralization - soft bones
In adults- Osteomalacia loss of bone minerals, soft bones
At risk: limited sun exposure (Vancouver winter)
Fat malabsorption
Elderly
Breastfed infants

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14
Q

Calcium Sources

A

Milk/dairy
Tofu
Seafood
Some vegetables and legumes

Spinach is low bioavailable
Dairy is good bioavailble

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15
Q

Digestion of Calcium

A

Convert Calcium salts to free Ca2+

Using Stomach acid - HCl

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16
Q

Absorption of Calcium

A
  1. Carrier mediated: TRPV6/ Calbindin / Ca-ATPase (enhanced by Vit D)
  2. Paracellular transport
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17
Q

Enhancers of Ca absorption

A

Protein
Sugars
Gastric activity

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18
Q

Inhibitors of Ca absorption

A

Oxalic acid, phytic acid
Divalent cations
Fibre
Fatty acids

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19
Q

Absorption of Calcium decreases with age due to

A

Less expression of calcium transporters
Less intake and synthesis of vitamin D
Lower stomach acidity

20
Q

Excretion of calcium

A

Enhanced with protein, caffeine and sodium

21
Q

Homeostasis of calcium

A

Extracellular Ca: (blood)

  • increased by PTH, calcitriol
  • decreased by calcitonin

Intracellular:
-regulated by cell uptake/secretion + release/sequestering in organelles

22
Q

Functions of Calcium

A 
Bone Mineralization
Muscle contraction 
Blood clotting
Signal transduction
Enzymes
Nerve transmission
23
Q

Nutrient Interactions of Calcium

A

Ca influences absorption of Iron, Phosphorus & Fatty acids

Absorption:
Enhanced by -protein , sugars, Vit D

Inhibited by -phytic acid and oxalic acid, fibre, fatty acids, divalent cations

Excretion:
Enhanced by protein, caffeine, sodium

24
Q

Calcium deficiency

A

Osteoporosis
Neuromuscular impairment
Risk: low intake, Vit D deficiency

25
Q

Excess Calcium - Toxicity

A

Hypercalcemia:

Lethargy, vomiting, heart arrhythmias

26
Q

phosphorus forms

A

Inorganic: Pi
Organic: phosphates - phospholipids, phosphorylated proteins

27
Q

Functions of phosphorus P

A

Structural component of Bone
Component of biological molecules: DNA, ATP, phospholipids
Regulation of enzyme function

28
Q

Sources of Pi Phosphorous

A

Widespread

Meats, dairy, legumes, grains

29
Q

Digestion of phosphates

A

Organic phos. Converted to inorganic P by phosphatases

30
Q

Absorption of P

A

Main is Paracellular diffusion

Can also happen via active transport

31
Q

Excretion of P

A

Urinary excretion is main

32
Q

Bioavailablity of Phosphorous

A

Decreases with high intakes of Ca or Mg (antacids)

33
Q

Homeostasis of P

A

Regulated by FGF23 & PTH - promotes urine excretion = lowers serum P

Increased serum P by 1,25(oh)2 = increases absorption, reabsorption, done resorption

34
Q

Phosphorous deficiency

A

Uncommon
Risk if: severe malnutrition, hyperthyroidism

Leads to rickets, osteomalacia

35
Q

Excess phosphorous

A

HyPOthyroidism, renal disease, excess Vit D
Leads to calcification of soft tissues & increases risk of heart disease

UL set.

36
Q

Magnesium Functions

A

Bone mineralization
Enzymatic function - structural cofactor (stabilize enzyme) ->** hydroxylation of vitamin D (25 hydroxylase
Ion channel flux - mg is a Ca channel blocker
Insulin signalling

37
Q

Digestion of Mg

A

None required

38
Q

Absorption of MG

A

Mg-specific transporter
Inhibited by high Mg concentration
Paracellular diffusion

39
Q

Bioavailability of Mg

A

Inhibited by: phytic acid, fibre, fatty acid, phosphorous

40
Q

Urinary excretion of Mg

A

Increased at high Mg levels

Decreased by PTH

41
Q

Homeostasis of Mg

A

Maintained through regulation of absorption and urinary excretion

PTH increases renal reabsorption, bone resorption, and w/ V D increased intestinal absorption

At high intakes, absorption if decreased and excretion is increased

42
Q

Nutrient interactions with mg

A
43
Q

Deficiency of Mg

A

Leads to low Ca, K, Vit D
Neuromuscular, cardiovascular, and CNS effects

Low intake is common, associated with increased risk of hypertension and type 2 diabetes

44
Q

Mg supplements have benefits for

A

May have benefits for sleep, migraines, and mood disorders

45
Q

Toxicity of magnesium

A

UL set based on harmful effects of excess intake from supplements

Nutrition FNH 351 (2 decks)

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