Blood Minerals

Question 1

What are the 3 main functions of iron?

Answer 1

• oxygen transport
• cofactor for non-haem enzymes (e.g. converts b-carotene to vitamin A)
• production of ATP

Question 2

What are the main dietary sources of iron?

Answer 2

Haem

• meat
• poultry
• fish
• eggs

Non-haem

• cereals
• pulses
• beans
• green vegetables
• fortified foods (eg milo)

Question 3

How much of haem iron is absorbed?

Answer 3

25%

Question 4

How much of non-haem iron is absorbed?

Answer 4

2-8%

Question 5

How is iron absorbed?

Answer 5

Iron is solubilised by acid from Fe3+ to Fe2+ (eg HCL or ascorbic acid (vitamin C)) in the duodenum/upper duodenum

Question 6

What is iron absorption dependant upon?

Answer 6

• iron content in foods
• iron in the body
• type of iron

Question 7

What can increase/decrease iron absorption?

Answer 7

Increase - vitamin C

Decrease - polyphenols (tannin in tea), oxalates (spinach), and phytates (cereals)

Question 8

What are the 3 key mechanisms in maintaining iron balance?

Answer 8

1. continuous reutilisation of Fe from catabolised RBC
2. regulation of absorption in the intestines
3. Fe-specific storage proteins that can be utilised when there are increased Fe requirements

Question 9

What is the NRV for iron?

Answer 9

RDI
8mg for males (19-70) and females (>50)
18 mg for females 19-50
Pregnancy 27mg/day

Question 10

What causes iron deficiency?

Answer 10

• inadequate intake
• some infants born with inadequate stores that are rapidly depleted, also delayed or inappropriate solids
• bleeding (gastric ulcers, menstrual loss, soft tissue damage)
• high sweat volume (ultra-endurance exercise)

Question 11

How are RBC produced when there is low blood oxygen?

Answer 11

Low blood oxygen stimulates erythropoietin hormone

This stimulates iron to enter the bone marrow and bind with Hb to produce RBC

Question 12

What is the majority of iron located in the body?

Answer 12

Haemoglobin (protein in rbc - transports O2 to tissues) 60-80%
Ferritin - reversible storage form of iron 15-30%

Question 13

What is transferrin?

Answer 13

Iron transporter

Question 14

Why might we see increase transferrin but low transferrin saturation?

Answer 14

Body is trying to compensate for low iron by increasing transferrin to transport iron around the body

Question 15

Why might we see low transferrin but no iron deficiency?

Answer 15

• liver disease
• malnutrition
• protein loss/low protein intake

Question 16

Why might we see low ferritin but iron is normal?

Answer 16

Ferritin is the storage of iron

Ferritin decreases to maintain iron in other tissues

Question 17

What is the role of selenium?

Answer 17

Cofactor for antioxidant enzyme glutathione peroxidase (protects glutathione -SH groups)

Question 18

What food sources does selenium come from?

Answer 18

• breads and cereals
• seafood
• poultry
• meat

Question 19

What is the role of zinc?

Answer 19

• involved in endogenous antioxidant enzyme processes
• cell signalling
• immune response
• growth and reproduction

Question 20

What food sources does zinc come from?

Answer 20

• red meat
• poultry
• nuts
• legumes
• wholegrains