REPLY
High-Dose Vitamin C and Iron Overload
Kris V. Kowdley, MD
18 May 2004 | Volume 140 Issue 10 | Pages 846-847
IN RESPONSE:
Sardi implies that medicinal iron alone was responsible for hemochromatosis in our patient rather than vitamin C taken in excess of 15 g/d for more than a decade. Although we agree that it is unclear which of the 2 factors (medicinal iron or megadoses of vitamin C) may have been primarily responsible, we believe it is impossible to incriminate (or exclude) one of these agents as the cause of iron overload. In fact, our case report maintained that greatly increased iron absorption may have originated with the medicinal iron but was facilitated by the conversion of iron to Fe3+ by ascorbic acid in the duodenum.
We disagree that there are inadequate data to support the concept that ascorbic acid may facilitate iron absorption. Fleming and colleagues' study in the elderly Framingham Heart Study cohort demonstrated that dietary ascorbic acid was related to high iron levels (1). Several recent studies have shown that ascorbic acid increased iron absorption 2.9-fold to 3.5-fold in iron-deficient and non–iron-deficient persons (2-4).
The apparent long duration of safe use of ascorbic acid in our patient before the development of iron overload is not surprising and in fact is typical of the pattern seen in primary iron overload disorders such as HFE-associated hemochromatosis. Although it is easy to argue that iron overload in this case may have been due to some other genetic cause, this appears highly improbable given the extreme rarity of primary disorders of iron overload among white persons in the absence of hemolysis or ineffective erythropoiesis.
We agree that it is impossible to know whether iron overload would have occurred in this patient in the absence of concomitant medicinal iron intake. However, we disagree with Sardi's dismissal of the strong possibility that megadoses of vitamin C, which has been clearly shown to increase iron absorption at much lower levels of intake, were a likely cause of iron overload in this case.
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Author and Article Information
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From University of Washington, Seattle, WA 98195.
1. Fleming DJ, Tucker KL, Jacques PF, Dallal GE, Wilson PW, Wood RJ. Dietary factors associated with the risk of high iron stores in the elderly Framingham Heart Study cohort. Am J Clin Nutr. 2002;76:1375-84. [PMID: 12450906].[Abstract/Free Full Text]
2. Cook JD, Reddy MB. Effect of ascorbic acid intake on nonheme-iron absorption from a complete diet. Am J Clin Nutr. 2001;73:93-8. [PMID: 11124756].[Abstract/Free Full Text]
3. Fidler MC, Davidsson L, Zeder C, Hurrell RF. Erythorbic acid is a potent enhancer of nonheme-iron absorption. Am J Clin Nutr. 2004;79:99-102. [PMID: 14684404].[Abstract/Free Full Text]
4. Diaz M, Rosado JL, Allen LH, Abrams S, Garcia OP. The efficacy of a local ascorbic acid-rich food in improving iron absorption from Mexican diets: a field study using stable isotopes. Am J Clin Nutr. 2003;78:436-40. [PMID: 12936926].[Abstract/Free Full Text]
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