Dietary iron

Although iron deficiency is a common problem, about 10% of the population are genetically at risk of iron overload (hemochromatosis), and elemental iron can lead to nonen2ymic generation of free radicals. Absorption of iron is stricdy regulated. Inorganic iron is accumulated in intestinal mucosal cells bound to an intracellular protein, ferritin. Once the ferritin in the cell is saturated with iron, no more can enter. Iron can only leave the mucosal cell if there is transferrin in plasma to bind to. Once transferrin is saturated with iron, any that has accumulated in the mucosal cells will be lost when the cells are shed. As a result of this mucosal barrier, only about 10% of dietary iron is normally absorbed and only 1-5% from many plant foods. 

Nelson, R.L. (1992). Dietary iron and colorectal cancer risk. Free Rad. Biol. Med. 12, 161-168. 

Siegers, C.P., Bumann, D., Trepkau, H.D., Schadwinkel, B. and Bareytton, G. (1992). Influence of dietary iron overload on cell proliferation and intestinal tumorigenesis in mice. Cancer Lett. 65, 245-249. 

Yoshiji, H., Nakae, D., Mizumoto, Y., Horiguchi, K., Tamura, K., Denda, A., Tsujii, T. and Konishi, Y. (1992). Inhibitory effect of dietary iron deficiency on inductions of putative preneoplastic lesions as well as 8-hydroxydeoxyguanosine in DNA and lipid peroxidation in the livers of rats caused by exposure to a choline-deficient L-amino acid defined diet. Carcinogenesis 13, 1227-1233. 

Younes, M., Trepkau, H.D. and Siegers, C.P. (1990). Enhancement by dietary iron of lipid peroxidation in mouse colon. Res. Commun. Chem. Pathol. Pharmacol. 70, 349-354. 

Retinopathy of prematurity Dietary iron overload (red wine, beer brewed in iron pots) Idiopathic haemochromatosis... 

Van Cauwenbbrgh, Hendrix P, Robberecht H, Deelstra H (1997) Daily dietary iron intake in Belgium using duplicate portion sampling. Z Lebensm Unters Forsch 205A 4oi-4o6. 

Sufficient dietary iron intake must be maintained in patients with anemia of CKD. Approximately 1 to 2 mg of iron is... 

Ccrklewski FL. 1980. Reduction in neonatal lead exposure by supplemental dietary iron during gestation and lactation in the rat. J Nutr 110 1453-1457. 

Hammad TA, Sexton M, Langenberg P. 1996. Relationship between blood lead and dietary iron intake in preschool children. A cross-section study. Ann Epidemiol 6(1) 30-33. 

Sources of Dietary Iron in Man and the Importance of Luminal Factors... 

Mucosal cells can take up iron from the lumen across their brush border membranes by at least two separate pathways, both of which are thought to be receptor mediated. Non-haem dietary iron seems most likely to be taken across the brush border membrane after reduction by an apical, membrane-bound, ferrireductase and subsequent transport of the Fe2+ by a divalent metal-ion transporter protein, known both as DCT1 and Nramp2. 

In the enterocyte as it enters the absorptive zone near to the villus tips, dietary iron is absorbed either directly as Fe(II) after reduction in the gastrointestinal tract by reductants like ascorbate, or after reduction of Fe(III) by the apical membrane ferrireductase Dcytb, via the divalent transporter Nramp2 (DCT1). Alternatively, haem is taken up at the apical surface, perhaps via a receptor, and is degraded by haem oxygenase to release Fe(II) into the same intracellular pool. The setting of IRPs (which are assumed to act as iron biosensors) determines the amount of iron that is retained within the enterocyte as ferritin, and that which is transferred to the circulation. This latter process is presumed to involve IREG 1 (ferroportin) and the GPI-linked hephaestin at the basolateral membrane with incorporation of iron into apotransferrin. (b) A representation of iron absorption in HFE-related haemochromatosis. 

Isoniazid for Dietary iron insuf- Lead paints... 

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