Iron Flashcards
Where is most iron used?
Bone marrow & erythrocytes (2-3g)
What are the main inhibitors and promoters of iron adsorption?
Phytic acid (inhibitor) also polyphenols, tannins, calcium Ascorbic acid (promoter) also meat, citric acid, alcohol
What are the reticulo-endothelial macrophages and what is their function?
Specialised group of macrophages present in the liver and spleen. Contain enzymes that digest red blood cells and recover iron that is then put back into the blood plasma
What is the total iron content of the body and how much of this is stored in the body and where?
Total- 3-4g
Stored in Liver- 1g
What are the RNI, EAR and LRNI for Men and Women and why are there differences? (mg/day)
Men (11-18) - 6.1, 8.7, 11.3
Men (19+) - 4.7, 6.7, 8.7
Women (11-50) - 8.0, 11.4, 14.8
Women (50+) - 4.7, 6.7, 8.7
Those who are having growth spurts require more iron as it is important for tissue and bone development (this also happens between 7 and 12 months). Menopausal women need more iron due to loss of blood in menstruation.
What are the average iron intakes of men and women and what % of them are below the LRNI?
11.6mg (19-64) 1% below LRNI
- 5mg (19-64) 23% below LRNI
- 6mg (11-18) 46% below LRNI
Where is haem iron found and why is it more bioavailable?
Haemoglobin and myoglobin
Absorption is not affected by other dietary constituents except Calcium
What are the main dietary sources of iron?
Cereals, meat products, veg and potatoes
How does haem iron get converted to non-haem iron?
Prolonged cooking at a high temperature
Transported into duodenal cell through haem carrier protein 1 (HCP1) and broken down by haem oxygenase
Describe the process of duodenal iron transport (include how different forms of iron enter the cell and what happens to them in the cell)
Ferric iron is reduced by dietary reducing agents (ascorbic acid) to the ferrous form of iron. On the erythrocyte the enzyme duodenal cytochrome B performs this action also. This iron then enters the cell through divalent metal transporter 1 (DMT1). DMT1 is a proton coupled symporter that needs acid present to drive iron absorption.
Haem iron enters the cell through haem carrier protein 1 (HCP1) and is immediately broken down by haem oxygenase to ferrous iron.
Once in the duodenal cell, ferrous ion can be oxidised to the ferric form once more and is then shed into the lumen and excreted. Or the ferrous iron can be transported through ferroportin into the plasma. Here it will be reoxidised by hephaestin to prevent oxidative damage. Transferrin then binds 2 Fe3+ ions (ferric ions) to transport the iron in the blood.
Why do meat, alcohol, tannins and calcium have affects on non-haem iron absorption?
Meat- digestion products (amino acids) stimulate CCK release which inhibits gastric emptying (increases time for absorption)
Alcohol- stimulates gastric acid secretion
Tannins- tightly bind to iron and form insoluble complexes
Calcium- helps tannins tight binding, directly competes
