Micronutrients

Question 1

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

Answer 1

Calcium - 807mg

Iron - 10.7mg

Zinc - 8.6mg

Iodine - 160ug

Selenium - 48ug

Question 2

What is a source of all the micronutrients?

Answer 2

Cereal

Question 3

Which micronutrients are found in meat?

Answer 3

Iron

Iodine

Selenium

Question 4

Which micronutrients are found in milk?

Answer 4

Calcium

Iodine

Question 5

Which micronutrients are found in fish?

Answer 5

Iodine

Selenium

Question 6

What is the aim of public health for micronutrients?

Answer 6

Meet daily requirements and reduce overintake

Question 7

Which population group is at risk of all micronutrient deficiencies?

Answer 7

Female 11-18yo

Question 8

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

Answer 8

Selenium

Question 9

What is LRNI?

Answer 9

Lower reference nutrient intake

Level of intake adequate for only 2.5% of the population

Question 10

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

Answer 10

Non-haem = iron salts/oxides, proteins

Haem = haemoglobin, myoglobin

Question 11

What does iron bind to in the blood?

Answer 11

Transferrin

Question 12

Where does most of the absorbed iron go?

Answer 12

Bone marrow (for Hb)

Question 13

What cells take up dead RBCs for iron recycling?

Answer 13

Reticulo-endothelial macrophages in liver and spleen

Question 14

How is iron stored and how much is stored?

Answer 14

In ferritin, largely present in liver

Up to 1g

Question 15

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

Answer 15

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

Question 16

Which type of ingested iron is best absorbed?

Answer 16

Haem iron ~25%

Question 17

Which micronutrient can block iron absorption?

Answer 17

Calcium

Question 18

What will prolonged cooking at high temperatures do to iron?

Answer 18

Convert haem iron to non-haem iron

Question 19

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

Answer 19

Fe (III)

Question 20

In what form must iron be to be absorbed?

Answer 20

Fe (II)

Question 21

What substances promote iron absorption? (6)

Answer 21

REDUCING AGENTS:

ASCORBIC ACID

MEAT DIGESTION PRODUCTS

Citric acid

Some spices (turmeric)

β-carotene

Alcohol

Question 22

What substances inhibit iron absorption? (4)

Answer 22

PHYTIC ACID

POLYPHENOLS

Tannins (tea, red wine)

Calcium

Question 23

How does alcohol promote iron absorption?

Answer 23

Stimulates gastric acid secretion to make iron more soluble

Question 24

How does phytic acid inhibit iron absorption?

Answer 24

Complexes with Fe (III) so it is insoluble

Question 25

What is the most common nutritional-related disorder?

Answer 25

Iron deficiency anaemia

Question 26

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

Answer 26

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

Question 27

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

Answer 27

Periods stop Increased risk of infertility Increased perinatal morbidity

Question 28

What are the consequences of iron deficiency anaemia on children?

Answer 28

Defective psychomotor development = impaired educational performance

Question 29

What are the consequences of iron deficiency anaemia on infants?

Answer 29

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

Question 30

What are the consequences of iron deficiency anaemia on adults?

Answer 30

Fatigue - impaired muscle oxidative phosphorylation

Question 31

What is hereditary haemochromatosis? (4)

Answer 31

Genetic Excess absorption of iron which is deposited in liver and pancreas Leads to liver cirrhosis and cancer Fairly asymptomatic until 30s

Question 32

What can secondary iron loading anaemias lead to?

Answer 32

(Eg. thalassaemia major) Leads to deposition of iron in heart due to constant iron transfusions to overcome Hb deficit

Question 33

What is the does the Fenton reaction describe?

Answer 33

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

Question 34

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

Answer 34

Haemoglobin, myoglobin Enzymes/cytochromes Redox reactions

Question 35

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

Answer 35

Liver Pancreatic secretions Kidneys Skin Muscles Prostatic fluid

Question 36

How is zinc returned to the intestines after absorption?

Answer 36

Pancreatic secretions

Question 37

What affects the bioavailability of zinc?

Answer 37

Phytic acid to animal protein ratio

Question 38

What ratio would give a high zinc bioavailability?

Answer 38

Low phytic acid to animal protein ratio <5

Question 39

What ratio would give a low zinc bioavailability?

Answer 39

High phytic acid to animal protein ratio >15

Question 40

What processes are zinc metalloenzymes involved in? (5)

Answer 40

Acid-base balance (carbonic anhydrase) Antioxidant defence (Cu|Zn superoxide dismutase) Bone metabolism (alkaline phosphatase) Nucleic acid synthesis (RNA polymerase) Protein digestion (carboxypeptidase A)

Question 41

What are the physiological roles of zinc? (5)

Answer 41

Metalloenzymes Bound zinc stabilises RNA and DNA structures (metal transcription factors) Neuromodulator in synaptic vesicles (esp. glutamine) Insulin granule formation Immune modulator

Question 42

What is acrodermatitis enteropathica and its characteristics?

Answer 42

Inborn error of zinc metabolism in gene coding Zip4 transporter in gut Dwarfism, dermatitis, diarrhoeal disease, poor immune function

Question 43

What would a mild zinc deficiency cause?

Answer 43

Similar, but less severe, symptoms to acrodermatitis enteropathica

Question 44

What symptoms would a zinc deficiency cause?

Answer 44

Dwarfism and hypogonadism

Question 45

What may cause a dietary zinc deficiency?

Answer 45

High levels of unleavened bread (no yeast/phytase activity) Geophagia = appetite suppressant and clay binds almost all metals

Question 46

Name the main families of selenoproteins. (4)

Answer 46

Glutathione peroxidases (GPx) Iodothyronine deiodinases (Dio) Selenoprotein P (SEPP1) Thioredoxin reductases (TrxR)

Question 47

What are glutathione peroxidases? (3)

Answer 47

Selenoproteins Antioxidant enzymes - protect lipid membranes from free radical damage Remove hydrogen peroxide, lipid/phospholipid/cholesterol hydroperoxides

Question 48

What is selenoprotein P?

Answer 48

Selenium carrier containing 10 selenocysteine residues

Question 49

What do thioredoxin reductases do?

Answer 49

Protect against free radical damage during DNA synthesis

Question 50

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

Answer 50

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

Question 51

What food is high in selenium?

Answer 51

Brazil nuts

Question 52

What intake of selenium would result in a deficiency?

Answer 52

<20ug/day

Question 53

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

Answer 53

Keshan disease - cardiomyopathy Kashin-Beck disease - osteoarthropathy (RURAL CHINA ONLY)

Question 54

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

Answer 54

>850ug/day (would be a combo of environmental and diet) 450ug/day

Question 55

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

Answer 55

1ug/L = blood 15,000ug = thyroid

Question 56

What does thyroid peroxidase catalyse? (2)

Answer 56

Iodination of tyrosine on thyroglobulin Synthesis of thyroid hormones

Question 57

Which gender is more susceptible to iodine deficiencies?

Answer 57

Female

Question 58

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

Answer 58

Hypothyroidism = low energy Some brain damage Cretinism