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MD1 Metabolism > Consequences of Malnutrition > Flashcards

Consequences of Malnutrition Flashcards

1
Q

In which type of vitamin is overdose more likely: lipid-soluble, or water-soluble?

A

Lipid-soluble

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2
Q

Which type of vitamin needs to be replenished constantly: lipid-soluble, or water-soluble?

A

Water-soluble

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3
Q

Are vitamin and mineral deficiencies a big problem in Australia?

A

Low level problem but could be contributing to chronic disease

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4
Q

Why do vitamin and mineral deficiencies occur?

A

Modern Western diet can be poorly balanced/not variable enough
Individual diet may miss specific sources
Crops can lack nutrients because of availability in soil
Other disorders/lifestyles can interfere with absorption

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5
Q

In whom are vitamin and mineral deficiencies of concern?

A

Pregnant women
Young children
Elderly people

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6
Q

What does production of vitamin D need?

A

Exposure of skin to UV or dietary intake

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7
Q

In what foods is vitamin D found?

A

Fatty fish
Oysters
Eggs
Fortified margarine

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8
Q

Where does vitamin D act as a hormone?

A

Intestines
Kidneys
Bones

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9
Q

What are the roles of vitamin D?

A

Bone-making and maintenance by maintaining blood concentrations of Ca and P

  • Enhances absorption from GIT
  • Enhances re-absorption from kidneys
  • Mobilises from bone into blood
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10
Q

How is vitamin D produced?

A

7-dehydrocholesterol > 2 steps in skin (using UV) > cholecalciferol (vitamin D3) > 1 step in liver/kidney > calcitriol

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11
Q

Is vitamin D3 active?

A

No

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12
Q

Is calcitriol active?

A

Yes

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13
Q

What happens in severe vitamin D deficiency in children?

A

Rickets

  • Failure of normal calcification of bones
  • Growth retardation
  • Skeletal abnormalities
    • Bent long bones of leg
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14
Q

Who are at higher risk of vitamin D deficiency?

A

Dark skinned people living very north/south
Fair skinned people who avoid sun exposure
Night shift workers, office workers, taxi drivers
Older people - skin, liver, and kidneys lose capacity to activate vitamin D
Older/disabled people who’re housebound/in care
People covered for religious reasons

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15
Q

Wat happens in vitamin D deficiency in adults?

A

Loss of Ca from bones > fractures

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16
Q

What is the role of calcium in the bones?

A

99% of body’s Ca in bones and teeth
Essential component of bone structure for rigid frame
Ca bank for blood levels Ca

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17
Q

What is the role of calcium in the blood?

A 
1% in blood and cells
Part of many enzymes
Mediates hormonal responses
Essential for blood coagulation
Used in muscle contraction
Needed for neuromuscular function
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18
Q

Who are at risk of rising blood calcium?

A

Breastfeeding babies whose intake of milk high

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19
Q

How are falling blood calcium levels elevated?

A
  1. Parathyroid hormone stimulates activation of vitamin D
  2. Vitamin D and parathyroid hormone stimulate Ca reabsorption in kidneys
  3. Vitamin D enhances Ca absorption in intestines
  4. Vitamin D and parathyroid hormone stimulate osteoclasts > break down bone > release Ca into blood
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20
Q

What do blood levels of calcium indicate?

A

Nothing - they’re always stable

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21
Q

How do you measure levels of calcium in bone?

A

No measures

Can measure bone mass and density

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22
Q

What foods in Australia are fortified?

A

Thiamine in bread
Folate and iodine in flour
Breakfast cereals voluntarily commonly fortified

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23
Q

What proportion of Australian women over 19 don’t have an adequate intake of folate?

A

9%

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24
Q

Who are recommended to take extra folate?

A

All women of childbearing age

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25
Q

What does a folate deficiency in pregnancy cause?

A

Neural tube development defects; eg: spina bifida

26
Q

What cellular processes need folate?

A 
DNA
- Replication
- Repair
- Methylation
Especially relevant during rapid cell division and development
27
Q

Why is it important to have adequate amounts of folate before you find out you’re pregnant?

A

Neural tube development complete by 4 weeks

Very rare for woman to know she’s pregnant at this time > don’t often know until 6-8 weeks

28
Q

What does folate deficiency in adults cause?

A

Macrocytic/megablastic anaemia

Characterised by large RBCs

29
Q

Why does macrocytic anaemia occur in folate deficiency?

A

Slow repair of DNA damage

30
Q

Is macrocytic anaemia because of folate deficiency common?

A

No, but some anticancer drugs can interfere with folate levels > deficiency

31
Q

How is macrocytic anaemia treated?

A

Extra folate

32
Q

What is the relationship between folate and vitamin B12?

A

Need each other for activation

33
Q

What is vitamin B12 needed for?

A

Regenerated levels of methionine

DNA and RNA synthesis

34
Q

Why do vitamin B12 levels decrease slowly?

A

Recycled for re-use

35
Q

Where is vitamin B12 found?

A

Only in animal products

Almost all of vitamin B12 in plants inactive > vegans at risk of deficiency

36
Q

How is folate activated?

A

Folate in food as polyglutamate = inactive
In intestine - breaks off glutamates > adds methyl groups > absorbed and delivered to cells = inactive
In cells trapped in inactive form
Vitamin B12 removes and keeps methyl group
- Removal of methyl activates folate
- Addition of methyl activates vitamin B12

37
Q

How does a vitamin B12 deficiency lead to damage to myelin sheaths of peripheral nerves?

A

Levels of metabolic intermediates like methylmalonine CoA build up
Cause damage to myelin sheath

38
Q

What are the symptoms of vitamin B12 deficiency?

A

Reduced performance on tests of intelligence and short-term memory
Creeping paralysis starting in extremities

39
Q

What are the symptoms of an inability to activate folate?

A

Megablastic anaemia

- Often 1st symptom of vitamin B12 deficiency

40
Q

What would be the effect of treating megablastic anaemia of a patient with vitamin B12 deficiency with folate?

A

Rapidly fix anaemia
Still have vitamin B12 deficiency
Peripheral nerve damage continues

41
Q

What is the number one cause of preventable intellectual disability in children?

A

Iodine deficiency

42
Q

What does a major iodine deficiency cause?

A

Goitre

43
Q

Why may have mild iodine deficiency recently re-emerged in Australia?

A

Lower salt diet

44
Q

Are difficulties in school caused by a mild iodine deficiency reversible with iodine supplementation?

A

Yes

45
Q

What does severe iodine deficiency during pregnancy cause?

A

Severe and irreversible physical and mental retardation = cretinism

46
Q

What is the most common deficiency in the world?

A

Fe

47
Q

What is iron a part of?

A

Haemoglobin and myoglobin
P450 enzymes
Lysosomal enzymes
Ribonucleotide reductase

48
Q

Why is iron never found free in the body?

A

Extremely toxic

49
Q

How is iron kept in the body?

A

Bound to transport/storage proteins

50
Q

From where is iron recycled in the body?

A

RBCs

51
Q

How are iron stores depleted?

A

Shedding of intestinal and skin cells

Blood loss through menstruation in women

52
Q

Why do children need more iron?

A

To increase blood volume

53
Q

What is thiamine used for in the body?

A

Essential part of coenzyme thiamine pyrophosphate

54
Q

What does severe thiamine deficiency cause?

A

Beriberi

  • Oedema
  • Muscle wasting
55
Q

Is thiamine deficiency common in Australia?

A

No, rare

Except when caused by alcoholism

56
Q

What are the dietary risks associated with alcoholism?

A

Low intake
Impaired absorption
Alterations in storage
Possibly increased excretion

57
Q

How can absorption be impaired in alcoholism?

A

Damage to cells lining intestine
Alterations in function of pancreas > reduced digestive enzyme production
Alterations in fat absorption limits intake of lipid soluble vitamins
- A
- E
- D

58
Q

How can storage be altered in alcoholism?

A

Decreased liver function > decreased vitamin A store

59
Q

What vitamins and minerals are vegans at risk of being deficient in?

A 
Vitamin B12
Vitamin D
Fe
Ca
Zn
60
Q

Why are calcium and vitamin D important in the elderly?

A

Vital for preventing loss of Ca from bones > reducing risk of fractures

61
Q

Why may the elderly develop deficiencies?

A 
Harder to shop for fresh foods
Harder to cook
Could be cooking for just 1
Tastes and appetites change
Dental problems/dentures can make chewing harder
Changes in digestion and absorption through
- Age
- Disease
- Medication

MD1 Metabolism (18 decks)

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