Iron in Health and Disease

Question 1

Facts about Iron

Answer 1

The second most abundant metal on earth.
Crucial for the survival of living organisms.
Cancer cells exhibit an iron-seeking phenotype.
Iron metabolism in cancer cells shifts to favour iron accumulation.

Question 2

What are Cytochromes?

Answer 2

Iron-containing proteins that shuttle electrons in ETC

Question 3

Why are iron-dependent enzymes required?

Answer 3

For DNA replication

Question 4

Why are Cytochrome p-450 enzymes essential?

Answer 4

For the production of steroids and cholesterol.
Eliminates toxins and variance in drug response amongst people of different ethnicities.

Question 5

Example of the antioxidant function of Iron

Answer 5

Catalase, which neutralises peroxidase

Question 6

Iron content in Adults

Answer 6

3 - 5g in total

Question 7

How much dietary iron is absorbed each day?

Answer 7

0.5 - 2 mg

Question 8

Iron balance is maintained by:

Answer 8

iron absorption

Question 9

What blood plasma transports Iron?

Answer 9

Transferrin (3%)

Question 10

How is iron stored in the liver?

Answer 10

as a ferritin 20%, also bone marrow and spleen

Question 11

What is Erythropoiesis?

Answer 11

Absorption related to body iron stores and rate

Question 12

What is the luminal phase?

Answer 12

Iron is solubilised by acid in the stomach and transported to
duodenum

Question 13

What is the mucosal/intracellular phase? (Iron)

Answer 13

Receives iron and stores as mucosal ferritin

Question 14

What is the release phase?

Answer 14

Mucosal ferritin transfers iron to mucosal transferrin and blood transferrin to circulation

Question 15

Iron storage and transport

Answer 15

• Blood transferrin delivers iron to bone marrow and other tissues
  ▪ When iron is plentiful, ferritin (storage) synthesis is upregulated, and the number of transferrin receptors decreases
  ▪ When iron stores are low, ferritin synthesis is reduced, and the transferrin receptor is upregulated
  ▪ When iron stores high, the liver converts some ferritin to Hemosiderin for storage
  ▪ Most of the iron in circulation comes from recycling of erythrocytes and not from daily intake

Question 16

Iron requirements

Answer 16

Birth to 6 months .27mg
7 to 12 months 11mg
1-3 y 7 mg
4-8 y 10 mg
14-18 y11 mg 15mg
19-50 y 8mg 18mg
51+ y 8 mg

Question 17

Iron requirements in pregnancy

Answer 17

27mg

Question 18

Iron requirements in lactation

Answer 18

9 mg

Question 19

2 forms of dietary iron

Answer 19

Haem: found in animal foods
Non-haem: found in plant foods

• Haem contributes 10-15% of total iron intake
• Non-haem accounts for 80% of iron consumption, but the absorption process is inefficient
  Affected by solubility enhancers or inhibitors during the same meal

Question 20

Factors affecting bioavailability: enhancers and inhibitors

Answer 20

Alcohol enhances iron absorption, between 20 and 30 percent
heavy drinkers absorb twice as much iron as normal
* Polyphenols in fruit, veg, wine and phytates ↓ , e.g. black tea, wheat bran, and oats can reduce iron absorption
* Polyphenols/phytate form insoluble complexes with iron in the gut
* However, it can be dose-dependent; some polyphenols may promote iron absorption
* Fibre does not inhibit absorption, but fibre-rich foods are often
phytate rich – phytic acid inhibits iron, calcium and zinc absorption
* Calcium negative effects on both haem and non-haem absorption –
depends on meal type, calcium content and other factors
* Physiologic or genetic variables may significantly impact iron
absorption in people with similar body iron stores, e.g. expression
of iron transporters and or/cellular location of iron transporters in
individuals

Question 21

Inhibition in a meal

Answer 21

Tea and toast absorption of non-haem from bread reduced by 60%
▪ Coffee with hamburger reduced non-haem absorption by 35%
▪ 1 glass of red wine reduced non-haem from bread-based meal
by 75%
▪ 1 glass of orange juice increased non-haem from hamburger
meal by 85%

Question 22

What is haemochromatosis?

Answer 22

▪ Genetic disorder: most common cause of chronic iron overload
▪ People with haemochromatosis absorb excessive amounts of iron from their diet
▪ Progressive accumulation of metal in organs esp, heart, endocrine organs, liver
▪ Cirrhosis, liver cancer, diabetes,
cardiomyopathy, arthritis
▪ Must inherit genes from both parents
▪ Treatment: regular venipuncture

Avoid:
▪ iron supplements
* raw seafood
* avoiding or reducing alcohol

Question 23

Consequences of iron deficiency anaemia IDA

Answer 23

Decreased work capacity or performance
Increased risk of infection
Increased risk of having a pre-term baby in pregnant women