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HUNT241 > Nutrition Lecture 10: Iron > Flashcards

Nutrition Lecture 10: Iron Flashcards

1
Q

What are rich food sources of iron?

A

Meat, pate, some seafood, red kidney beans, fortified foods

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2
Q

What is bioavailability defined as?

A

The proportion of intake of a nutrient that is absorbed and utilized

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3
Q

What is iron bioavailability influenced by?

A
  • Host-related factors
  • Chemical form (haem vs non-haem Fe)
  • Enhancers
  • Inhibitors
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4
Q

What is the relationship between iron status and iron absorption?

A

Increased serum ferritin decreases absorption

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5
Q

What host-related factors affect iron absorption

A
  • Pregnancy
  • Recent iron intake
  • Genetics
  • Disease states
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6
Q

What is the absorption of Haem Fe?

A

25-30%

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7
Q

What is the absorption of Non-haem Fe?

A

5-15%

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8
Q

Haem vs non-haem iron

A
  • Haem iron absorption is considerably higher
  • bigger variability in non-haem iron
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9
Q

What form of iron does meat provide?

A

Meat doesn’t just provide Haem iron, it provides both

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10
Q

Generally, 90% of iron consumed is…

A

Non-haem

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11
Q

What are enhancers of iron absorption?

A
  • Vitamin C (ascorbic acid?
  • Meat, fish and poultry (not eggs and milk just flesh foods)
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12
Q

What are inhibitors of iron absorption?

A
  • Phytate
  • Tannins (tea and coffee)
  • Oxalic acid
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13
Q

Where is iron absorption of Haem iron?

A

Mainly in duodenum

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14
Q

How is Haem iron absorbed?

A
  • Haem split from globin
  • Haem absorbed intact
  • Ferrous iron released in enterocyte
  • Joins common pool in enterocyte with NHFe
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15
Q

Where is iron absorption of non-haem?

A

Mainly in duodenum

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16
Q

How is non-haem iron absorbed?

A
  • Lumen of the gut has a neutral pH, so will be in ferric 3+ form
  • Duodenal cytochrome B reduces ferric form into ferrous form
  • Then absorbed through the DMT1
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17
Q

What are the forms of iron in the body?

A
  • Haemoglobin
  • Myoglobin
  • Enzyme Fe
  • Storage Fe
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18
Q

What percent of body Fe is haemoglobin?

A

67%

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19
Q

What is the function of Haemoglobin?

A

Transports O2

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20
Q

What percent of body Fe is myoglobin?

A

4%

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21
Q

What is the function of myoglobin?

A

O2 storage in tissues

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22
Q

What percent of body Fe is enzyme Fe?

A

0.2%

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23
Q

What is the function of enzyme Fe?

A
  • Energy metabolism
  • Neurotransmitter formation
  • Bacterial killing in leukocytes
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24
Q

What percent of body Fe is storage Fe?

A

27% - depends

25
Q

Where is Fe stored in the body?

A

Liver, spleen, bone marrow

26
Q

How is Fe involved in transport?

A

Transport Fe is in the form of transferrin (0.1% body Fe)

27
Q

How is iron excretion controlled?

A

Its not, all of the control is happening at the absorption step

28
Q

How is iron lost?

A

Epithelial cells and Fluids

29
Q

What epithelial cells lose iron?

A
  • Skin (0.2mg)
  • Intestinal mucosal cells (0.1mg)
  • Urinary tract cells (0.1mg)
30
Q

What fluids lose iron?

A
  • Blood in gut (0.4mg)
  • Bile (0.2mg)
  • MENSTRATION
31
Q

Men vs Women iron losses per day

A

Men = 1mg/day
Women = 2mg/day

32
Q

Why is reutilisation of iron so important?

A

To form all the erythrocytes needed you would need approximately 30mg per day BUT we only absorb about 1-2mg

33
Q

Where does majority of iron reutilisation come from?

A

Old red blood cells in spleen and liver

34
Q

What are the concequences of iron deficiency anemia?

A
  • Decreased growth
  • Behavioural disturbances
  • Decreased cognitive function
  • Fatigue
  • Spoon-shaped nails
35
Q

What are the consequences of the depletion of iron stores?

A

Can see same symptoms of anaemia - you are more at risk for anaemia

36
Q

What groups are at risk of iron deficiency?

A
  • Pre-term infants
  • Infants
  • Toddlers
  • Menstruating women
  • Pregnant women
  • Blood donors
37
Q

When is there are high requirement for iron?

A
  • Growth
  • Blood loss
  • Pregnancy
38
Q

What is recommended for people with anaemia?

A

Iron supplements or IV infusion

39
Q

What is recommended for people with non-anaemic iron deficiency?

A

Diet, supplements

40
Q

What is acute iron toxicity?

A

Unintentional overdose of iron tablets, Lethal oral dose = 200mg/kg

41
Q

What is hereditary haemochromatosis?

A

A homozygous genetic condition that causes poor control of iron absorption

42
Q

What mutation is present in people with hereditary haemochromatosis?

A

C282Y mutation on the HFE gene

43
Q

In people with hereditary haemochromatosis, where does iron accumulate?

A

In liver, pancreas and heart

44
Q

What is the EAR for iron?

A

Men = 6mg/day
Women = 8mg/day

45
Q

What is the RDI for iron?

A

Men = 8mg/day
Women = 18mg/day

46
Q

Why is RDI so high for women?

A

There is a big skew of women, because there is large variety in blood lost during menstruation between women

47
Q

How does Heme iron enter the enterocyte?

A
  • Comes in through heme transporter
  • Is then acted on by the enzyme oxygenase to become non-heme iron
48
Q

What transporter brings heme iron into the enterocyte?

A

Heme transporter

49
Q

What enzyme converts heme iron into non-heme iron once inside the enterocyte?

A

Heme Oxygenase

50
Q

What form does non-heme iron arrive at the enterocyte in?

A

In ferric form (Fe3+)

51
Q

What enzyme transforms non-heme iron from ferric (Fe3+) to ferrous form (Fe2+)?

A

Duodenal cytochrome B - this is a reduction step

52
Q

How is non-heme iron (once transformed into ferrous form) transported into the enterocyte?

A

Through DMT1

53
Q

Once inside the enterocyte, what are the two options for iron?

A
  1. Stored as ferritin
  2. Transported out of the enterocyte
54
Q

How is iron stored as ferritin inside the enterocyte?

A

In muscosal ferritin

55
Q

What transporter transports iron out of the enterocyte (it is all in ferrous form)?

A

Ferroportin 1

56
Q

What needs to happen to ferrous iron (Fe2+) once it is transported out of the enterocyte?

A

Needs to be oxidised back to ferric form (Fe3+) - as ferrous form is very reactive

57
Q

How is ferrous iron (Fe2+) transformed back to ferric iron (Fe3+) outside the enterocyte?

A

By hephaestin

58
Q

How is newly transformed Fe3+ iron, out of the enterocyte, transported around the body?

A

Bound to plasma transferrin

HUNT241 (22 decks)

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