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food energy and nutrients > iron > Flashcards

iron Flashcards

1
Q

iron is an essential type of what

A

mineral or trace element

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2
Q

why is iron in excess bad

A

cos its extremely toxic as it reacts readily with oxygen

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3
Q

what is the most common nutritional deficiency worldwide

A

iron efficiency anaemia (500-600 million).

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4
Q

what 2 basic forms is iron found in

A

haem or non-haem

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5
Q

what is haemoglobin( Hb)

A

a type of haem protein
Component of red blood cells and transports oxygen round the body

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6
Q

what is myoglobin and wheres it found

A

Oxygen-transporting protein of muscle (similar to haemoglobin in function)

is in certain skeletal muscle cells storing oxygen for when muscle requires oxygen for aerobic respiration during exercise and muscle contraction

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7
Q

what form of iron do animal products have

A

haem form

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8
Q

what form of iron do plant products have

A

non haem form
This form is less efficiently absorbed

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9
Q

what is Ferrous Iron (Fe 2+)

A

reduced form - most commonly found in food.

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10
Q

what is Ferric Iron (Fe 3+)

A

Oxidised form - to be bound to transferrin for transport.

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11
Q

what is haem

A

A chemical complex with a central iron atom that forms the oxygen binding part of haemoglobin and myoglobin.

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12
Q

what is haem iron

A

Iron found in haemoglobin and myoglobin of animal foods.

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13
Q

what is non haem iron

A

Iron in plants and in animal foods that is not part of haemoglobin or myoglobin.

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14
Q

what are the 2 valency states iron exists in

A

Fe 2+ or Fe3+

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15
Q

explain how the oxidised and reduced form of iron can be produced by REDOX

A

The reduced form Fe2+ can be oxidised into the oxidised form Fe3+. Oxidised form Fe3+ can be reduced into reduced form Fe2+

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16
Q

how do we mask irons presence

A

by binding it onto proteins

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17
Q

what is transferrin

A

Protein synthesised in the liver. It transports iron in the blood to erythroblasts to make haem.

it is a transport protein

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18
Q

what is ferritin

A

Major storage form of iron - a complex of iron and apoferritin.

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19
Q

whats it called when no protein is bound to ferritin

A

apoferritin when no iron protein bound to it. But when is bound its called ferritin

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20
Q

tissues take oxygen from haemoglobin for what

A

aerobic respiration

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21
Q

what is the total iron in the body of men and women and why the difference

A

~3800mg in men and ~2300mg in women.

Men have more iron than females as are more muscular and cos have larger blood circulation volume so more red blood cells

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22
Q

what percentage of iron in the body in haemoglobin is in erythrocytes (red blood cells)

A

60-70%

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23
Q

what percentage of iron in the body is in muscle myoglobin

A

10%

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24
Q

what percentage of iron in the body is in storage pools in liver and reticulo-endothial (macrophage) system as ferritin (in liver)and haemosiderin (in macrophages in blood)

A

20-30%

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25
Q

what percentage of iron in body is in iron containing enzymes

A

1%

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26
Q

what percentage of iron in the body is in plasma transport pool bound to transferrin.

A

< 0.2%

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27
Q

there is constant recycling between what

A

functional and non-functional pools

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28
Q

erythrocytes have a lifespan of what

A

120 days

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29
Q

haemoglobin is not a storage from of what

A

iron

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30
Q

what are the functions of iron

A

Oxygen transport and storage - haemoglobin and myoglobin.

Iron containing enzymes, particularly those involved in energy metabolism and energy production, e.g. cytochromes, NADH dehydrogenase, as well as enzymes used in metabolism and storage.

Immune function – necessary for optimal immune function.

Pro-oxidant activity, is potentially harmful as free radicals damage body. Disturbances in iron metabolism may be pathogenic.

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31
Q

whats the function of haemoglobin and of myoglobin in oxygen transport and storage

A

Haemoglobin (Hb) - transports oxygen round the body.

Myoglobin - stores oxygen in muscles and tissues.

32
Q

explain oxygen transport and storage

A

Iron is stabilised in ferrous (Fe 2+) state in haem complex.

Interaction with adjacent globin protein allows it to bind reversibly with oxygen.

Allows oxygen (also potentially toxic) to be safely distributed and stored round the body.

Haemoglobin also binds CO2 and transports it to lungs for exhalation.

33
Q

name some dietary sources of haem iron

A

Food of animal origin
Liver
Red meat
Poultry
Fish

34
Q

name some dietary sources of non haem iron

A

Animal and plant tissues
Cereals
Vegetables
Nuts
Eggs
Fish
Meat
(Fortified foods)

SACN (2010) concluded that reducing total red meat consumption of high consumers down to 70g/d would have little effect on proportion of adults with iron intakes <LRNI

35
Q

name some meat, cereal, fruit and veg, and dairy sources that are high in iron

A

meat:
black pudding
liver
chicken
pate
venison

cereal:
fortified bran flakes
fortified cocopops

fruit/veg:
legumes
lentils

dairy:
eggs

36
Q

what does absorption mean

A

uptake of a nutrient into the intestinal mucosa and its transfer into the body.

37
Q

what does bioavailability mean

A

proportion of a nutrient that is taken up and transferred by the intestinal mucosa.

38
Q

what is the most bioavailable form of iron

A

haem iron

20-30% absorption from haem containing foods
1-10% absorption from non-haem sources

39
Q

how many mg/d of iron absorbed from the diet is used to replace lost iron

A

1mg/d

40
Q

what does hepcidin mean

A

principal regulator of iron absorption (a peptide).

41
Q

explain hepcidin in terms of iron stores

A

Acts by directly binding to and degrading the iron exporter molecule on the cellular membrane and prevents iron from leaving the cell.

When iron stores are adequate/high, hepcidin production increases.

When iron stores are low or requirements are increased, hepcidin production decreases.

If hepcidin regulation is defective iron overload may result.

42
Q

what percentage of absorption means deficiency

A

40%
If no deficiency, ~15%.

43
Q

what is iron absorption enhanced by

A

by stomach acidity, but reduced by achlorhydria (decreased acid production in stomach) and antacids.

44
Q

explain the haem iron absorption in meat

A

Haem iron in meat is 40% total Fe
of which 15-35 % is absorbed.
relatively little affected by diet.

45
Q

what are some inhibitors of non haem iron absoption

A

Phytates (wholegrain cereals, seeds, nuts)
Polyphenols, e.g. tannins (tea, coffee, cocoa, red wine)
Oxalate
Phosphorus
Calcium
Soy protein

46
Q

what are some promotors of non haem iron absorption

A

Ascorbic and citric acids (ferric => ferrous)
Cysteine peptides in meat

47
Q

Iron homeostasis maintained to minimise risk of what

A

iron toxicity

48
Q

Absorption of iron from GI tract regulated by what

A

systemic need.

49
Q

Risk of damage by free reactive iron limited by what

A

series of organic molecules which bind free iron and carry it to functional sites or to storage depots.

50
Q

The main pool of ferritin is in the what and what does it act as

A

liver which acts as a buffer pool for iron excess to requirements - 25% of body iron.

51
Q

Iron turnover driven by what

A

formation of and destruction of haemoglobin in erythrocytes (life span 120 days).

52
Q

in iron metabolism what is engulfed and destroyed by macrophages.

A

Senescent erythocytes

53
Q

in metabolism of iron, iron is released and incorporated into what

A

into transferrin.

54
Q

in metabolism where does transferrin take iron to

A

takes iron to erythroblasts of bone marrow to make new red blood cells.

55
Q

in the body where does transferrin transport iron to and why

A

Transferrin transports iron to tissues for the synthesis of haem or storage in ferritin and haemosiderin.

it also transports iron into muscle, bone, and liver

56
Q

what does homeostasis mean

A

property of a system to maintain balance or functioning within a normal range.

57
Q

describe excretion paths for iron

A

No defined excretory paths.

58
Q

what does Intestinal uptake and transfer of iron =

A

iron losses & iron needed for growth & reproduction.

Losses have to be replaced by dietary intake.

59
Q

whats are ex of iron losses

A

menstruation

Bleeding or blood donation

Hookworm - infestation determined by total egg count

60
Q

what are the iron requirement values for during pregnancy

A

total basal 240 mg
+ blood 500mg
+ foetus and placenta 300mg

61
Q

what are the iron requirements needed in breast milk

A

0.25-0.34 mg/day

62
Q

why do children need iron

A

fir growth

63
Q

what is the iron requirement in blood donation

A

200mg (0.5mg Fe/ml)

64
Q

what are supply’s of iron

A

Food iron content

Type of iron
- haem
- non-haem

Absorption
- promoters
- inhibitors

65
Q

what are some times when iron is required

A

Growth
Pregnancy
Lactation

66
Q

iron is metabolised from what

A

stores

67
Q

what are the DRVs of iron for males

A

EAR 8.7 mg, RNI 11.3 mg.

68
Q

what are the DRVs of iron for menstruating women

A

EAR 11.4 mg, RNI 14.8 mg.

Losses in menstruation are not normally distributed and RNI not for 10% of women with highest menstrual losses.

69
Q

describe the process of iron deficiency development

A

starts with normal cells
decrease in iron stores
decrease in iron transport
(iron deficiency starts to develop)
fall in haemoglobin synthesis
anaemia

70
Q

what are causes of iron deficiency in uk

A

Menstruation, 25%
Aspirin/NSAID use, 13%
Colonic carcinoma, 8%
Gastric carcinoma, 5%
Benign gastric ulceration, 5%
Angiodysplasia, 5%
Coeliac disease, 5%
Blood donation, 5%
other 29%

71
Q

what is iron deficiency anaemia and its affects

A

Haemoglobin concentration below age-appropriate range for healthy people.

Due to iron deficiency.

Responds to iron repletion.

Effects
Reduced size and haemoglobin
density of erythrocytes.
- Microcytic and hypochromic RBC

72
Q

what are common symptoms of iron deficient anaemia

A

Tiredness and lethargy (lack of energy)
Shortness of breath
Heart palpitations (noticeable heartbeats)
Pale complexion

73
Q

what are less common symptoms of iron deficiency anaemia

A

headache
Tinnitus
Altered sense of taste
Feeling itchy
Sore orabnormally smooth tongue
Hair loss
Pica
Difficulty swallowing (dysphagia)
Painful ulcers on corners of mouth
Spoon-shaped nails (koilonychia)

74
Q

whos most at risk of iron deficiency

A

Infants over 6 months, toddlers and adolescents.

Menstruating women.

Pregnant women.

Older people.

People consuming diets low in iron and high in iron absorption inhibitors like phytate.

Individuals with high blood losses.

75
Q

explain iron deficiency treatment

A

Aim:
Restore haemoglobin levels and red cell indices to normal, and to replenish iron stores.

Address underlying causes.

Ferrous sulphate 200mg tablets 2-3 times/day (3 months).
Or ferrous fumarate / ferrous gluconate tablets

If dietary deficiency is thought to be a cause, advise on iron-rich foods and consider referral to dietitian.

Monitor patient to ensure adequate response to treatment.

76
Q

explain acute and sub chronic iron toxicity

A

Tends to occur in children – accidental ingestion of supps.

High doses of 50-220mg/d can cause GI effects: nausea, constipation, abdominal pain, diarrhoea and vomiting.

77
Q

explain chronic toxicity of iron - haemochromatosis

A

Autosomal recessive genetic disorder

Occurs in 1 in 300.

Unregulated dietary absorption with gradual accumulation of iron in tissues. Leads to irreversible tissue damage.

food energy and nutrients (32 decks)

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