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The Vitamin C/Ferritin/Iron Connection Ferritin is found in most cells in the body and in the serum. Its function in serum is not known. It is a large complex molecule that sequesters iron. It has 24 protein subunits of two types. These subunits form a structure with a hollow cavity that can sequester 4500 atoms of iron. The iron can enter and exit the ferritin cavity and is part of the metabolic pool of reactive metals in the cell. Iron is necessary for enzyme function and in the mitochondria. The ferritin complexes are continually being recycled within the cell.Lyosomes are organelles within the cell that sequester and detoxify cellular material that could damage the cell. Ferritin complexes combine together to form even larger complexes that are engulfed by the lyosomes. Once in the lyosomes, the ferritin is converted to hemosiderin, a stable and non-reactive mixture of iron, protein and lipid. The iron is in a non-reactive state and not readily available to the cell. Ascrobic acid decreases the migration of ferritin complexes to the lyosomes, thus directly increasing the amount of ferritin-sequestered iron in the cell and indirectly the reactive iron, since iron can then move out of the ferritin molecule. (see diagram below) Some tissues such as myocardium in the heart have a limited ability to make ferritin. Therefore it has less ability to sequester any free iron released into the body to prevent it from depositing in and damaging the heart. Since vitamin C increases the amount of iron circulating through the body, the myocardium's lack of ferritin makes it extra vulnerable to iron damage. This is the probable mechanism of vitamin C-induced cardiomyopathy. By increasing the pool of metabolically active iron in the cell, vitamin C increases the pool of iron available for chelation by Desferal. However, too much free iron can cause heart and other problems; thus moderate doses of vitamin taken shortly after starting Desferal infusions will provide optimal iron removal. People who are heavily iron overloaded should not ingest foods such as citrus and some vitamins in large quantities that would give them, for example, a gram (1000 mg) of ascorbic acid a day. <page 1> <page 2> References: 'Ascorbic Acid and Ferritin Catabolism,' Nutr Rev, 47:218-219, 1989. Cohen A, Cohen IJ, Schwartz E. 'Scruvy and altered iron stores in thalassemia major.' NEJM, 304:158-160, 1981. Hoffman, KE, Yanelli K, Bridges KR. 'Ascorbic acid and iron metabolism: alterations in lysosomal function.' Am J Clin Nutr, 54:1188S-92S, 1991. Nienhuis AW. 'Vitamin C and Iron.' NEJM, 304:170-71, 1981. |
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