Iron in Health and Disease Flashcards
Facts about Iron
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.
What are Cytochromes?
Iron-containing proteins that shuttle electrons in ETC
Why are iron-dependent enzymes required?
For DNA replication
Why are Cytochrome p-450 enzymes essential?
For the production of steroids and cholesterol.
Eliminates toxins and variance in drug response amongst people of different ethnicities.
Example of the antioxidant function of Iron
Catalase, which neutralises peroxidase
Iron content in Adults
3 - 5g in total
How much dietary iron is absorbed each day?
0.5 - 2 mg
Iron balance is maintained by:
iron absorption
What blood plasma transports Iron?
Transferrin (3%)
How is iron stored in the liver?
as a ferritin 20%, also bone marrow and spleen
What is Erythropoiesis?
Absorption related to body iron stores and rate
What is the luminal phase?
Iron is solubilised by acid in the stomach and transported to
duodenum
What is the mucosal/intracellular phase? (Iron)
Receives iron and stores as mucosal ferritin
What is the release phase?
Mucosal ferritin transfers iron to mucosal transferrin and blood transferrin to circulation
Iron storage and transport
- 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
Iron requirements
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
Iron requirements in pregnancy
27mg
Iron requirements in lactation
9 mg
2 forms of dietary iron
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
Factors affecting bioavailability: enhancers and inhibitors
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
Inhibition in a meal
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%
What is haemochromatosis?
▪ 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
Consequences of iron deficiency anaemia IDA
Decreased work capacity or performance
Increased risk of infection
Increased risk of having a pre-term baby in pregnant women
