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BMS15 > Micronutrients > Flashcards

Micronutrients Flashcards

1
Q

How much of each micronutrient do we need each day? (5)

A

Calcium - 807mg

Iron - 10.7mg

Zinc - 8.6mg

Iodine - 160ug

Selenium - 48ug

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2
Q

What is a source of all the micronutrients?

A

Cereal

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3
Q

Which micronutrients are found in meat?

A

Iron

Iodine

Selenium

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4
Q

Which micronutrients are found in milk?

A

Calcium

Iodine

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5
Q

Which micronutrients are found in fish?

A

Iodine

Selenium

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6
Q

What is the aim of public health for micronutrients?

A

Meet daily requirements and reduce overintake

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7
Q

Which population group is at risk of all micronutrient deficiencies?

A

Female 11-18yo

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8
Q

Which micronutrient deficiency is most common (has the most risk groups)?

A

Selenium

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9
Q

What is LRNI?

A

Lower reference nutrient intake

Level of intake adequate for only 2.5% of the population

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10
Q

What are the two types/forms in which iron can be ingested?

A

Non-haem = iron salts/oxides, proteins

Haem = haemoglobin, myoglobin

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11
Q

What does iron bind to in the blood?

A

Transferrin

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12
Q

Where does most of the absorbed iron go?

A

Bone marrow (for Hb)

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13
Q

What cells take up dead RBCs for iron recycling?

A

Reticulo-endothelial macrophages in liver and spleen

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14
Q

How is iron stored and how much is stored?

A

In ferritin, largely present in liver

Up to 1g

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15
Q

How can iron be lost from the body after absorption from the intestines?

A

Shedding of cells lining areas like skin, ureters, vagina, etc.

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16
Q

Which type of ingested iron is best absorbed?

A

Haem iron ~25%

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17
Q

Which micronutrient can block iron absorption?

A

Calcium

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18
Q

What will prolonged cooking at high temperatures do to iron?

A

Convert haem iron to non-haem iron

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19
Q

What is most of the dietary non-haem iron in the form of?

A

Fe (III)

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20
Q

In what form must iron be to be absorbed?

A

Fe (II)

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21
Q

What substances promote iron absorption? (6)

A

REDUCING AGENTS:

ASCORBIC ACID

MEAT DIGESTION PRODUCTS

Citric acid

Some spices (turmeric)

β-carotene

Alcohol

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22
Q

What substances inhibit iron absorption? (4)

A

PHYTIC ACID

POLYPHENOLS

Tannins (tea, red wine)

Calcium

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23
Q

How does alcohol promote iron absorption?

A

Stimulates gastric acid secretion to make iron more soluble

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24
Q

How does phytic acid inhibit iron absorption?

A

Complexes with Fe (III) so it is insoluble

25
Q

What is the most common nutritional-related disorder?

A

Iron deficiency anaemia

26
Q

What are the main causes of iron deficiency anaemia? (5)

A

Low bioavailability of iron in food

Parasitic infections - hookworms cause blood loss

Infections (iron locked in macrophages)

Female - period blood

Children, teens, pregnancy, obesity - increasing requirements

27
Q

What are the consequences of iron deficiency anaemia on reproductive functions? (3)

A

Periods stop

Increased risk of infertility

Increased perinatal morbidity

28
Q

What are the consequences of iron deficiency anaemia on children?

A

Defective psychomotor development = impaired educational performance

29
Q

What are the consequences of iron deficiency anaemia on infants?

A

Increased risk of infection of upper respiratory tract and GI tract (impaired immunity)

30
Q

What are the consequences of iron deficiency anaemia on adults?

A

Fatigue - impaired muscle oxidative phosphorylation

31
Q

What is hereditary haemochromatosis? (4)

A

Genetic

Excess absorption of iron which is deposited in liver and pancreas

Leads to liver cirrhosis and cancer

Fairly asymptomatic until 30s

32
Q

What can secondary iron loading anaemias lead to?

A

(Eg. thalassaemia major)

Leads to deposition of iron in heart due to constant iron transfusions to overcome Hb deficit

33
Q

What is the does the Fenton reaction describe?

A

Formation of hydroxyl radicals and superoxide ions which damage DNA and cell membranes (perioxidation)

34
Q

What are the main functional roles of iron? (3)

A

Haemoglobin, myoglobin

Enzymes/cytochromes

Redox reactions

35
Q

Where is zinc moved to from the plasma? (6)

A

Liver

Pancreatic secretions

Kidneys

Skin

Muscles

Prostatic fluid

36
Q

How is zinc returned to the intestines after absorption?

A

Pancreatic secretions

37
Q

What affects the bioavailability of zinc?

A

Phytic acid to animal protein ratio

38
Q

What ratio would give a high zinc bioavailability?

A

Low phytic acid to animal protein ratio <5

39
Q

What ratio would give a low zinc bioavailability?

A

High phytic acid to animal protein ratio >15

40
Q

What processes are zinc metalloenzymes involved in? (5)

A

Acid-base balance (carbonic anhydrase)

Antioxidant defence (Cu|Zn superoxide dismutase)

Bone metabolism (alkaline phosphatase)

Nucleic acid synthesis (RNA polymerase)

Protein digestion (carboxypeptidase A)

41
Q

What are the physiological roles of zinc? (5)

A

Metalloenzymes

Bound zinc stabilises RNA and DNA structures (metal transcription factors)

Neuromodulator in synaptic vesicles (esp. glutamine)

Insulin granule formation

Immune modulator

42
Q

What is acrodermatitis enteropathica and its characteristics?

A

Inborn error of zinc metabolism in gene coding Zip4 transporter in gut

Dwarfism, dermatitis, diarrhoeal disease, poor immune function

43
Q

What would a mild zinc deficiency cause?

A

Similar, but less severe, symptoms to acrodermatitis enteropathica

44
Q

What symptoms would a zinc deficiency cause?

A

Dwarfism and hypogonadism

45
Q

What may cause a dietary zinc deficiency?

A

High levels of unleavened bread (no yeast/phytase activity)

Geophagia = appetite suppressant and clay binds almost all metals

46
Q

Name the main families of selenoproteins. (4)

A

Glutathione peroxidases (GPx)

Iodothyronine deiodinases (Dio)

Selenoprotein P (SEPP1)

Thioredoxin reductases (TrxR)

47
Q

What are glutathione peroxidases? (3)

A

Selenoproteins

Antioxidant enzymes - protect lipid membranes from free radical damage

Remove hydrogen peroxide, lipid/phospholipid/cholesterol hydroperoxides

48
Q

What is selenoprotein P?

A

Selenium carrier containing 10 selenocysteine residues

49
Q

What do thioredoxin reductases do?

A

Protect against free radical damage during DNA synthesis

50
Q

Why is the population intake of selenium below the LRNI? (2)

A

Food processing - bread-making technology uses low-Se and low-protein wheat

People consume less bread

51
Q

What food is high in selenium?

A

Brazil nuts

52
Q

What intake of selenium would result in a deficiency?

A

<20ug/day

53
Q

What are the selenium deficiency diseases and what are they characterised by? (2)

A

Keshan disease - cardiomyopathy

Kashin-Beck disease - osteoarthropathy

(RURAL CHINA ONLY)

54
Q

What intake of selenium would be toxic? What is the safe upper limit?

A

> 850ug/day (would be a combo of environmental and diet)

450ug/day

55
Q

What are the fasting levels of iodine in the blood and thyroid?

A

1ug/L = blood

15,000ug = thyroid

56
Q

What does thyroid peroxidase catalyse? (2)

A

Iodination of tyrosine on thyroglobulin

Synthesis of thyroid hormones

57
Q

Which gender is more susceptible to iodine deficiencies?

A

Female

58
Q

What effect does iodine deficiency have (from mild to severe)?

A

Hypothyroidism = low energy

Some brain damage

Cretinism

BMS15 (4 decks)

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