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Nutritional Science Research Group Division of Cancer Prevention, NCI, NIH Bethesda, MD 20892
Nutritional Science Research Group Division of Cancer Prevention, NCI, NIH Bethesda, MD 20892 Grand Forks Human Nutrition Research Center United States Department of Agriculture Grand Forks, ND 58203
Dear Editor:
The article by Venn et al. (1) provides evidence that selenium supplements do not influence plasma total homocysteine (tHcy) concentrations in New Zealand men and women. It is certainly possible, as the authors conclude, that tHcy might be influenced by selenium status in populations with very low selenium status, such as in some parts of China but not in situations where mild deficiency exists such as in New Zealand. In fact our preclinal studies suggest that the greatest differences in tHcy are between rats fed a severely deficient diet (<2 ng selenium/g diet) and those fed a moderately selenium-deficient diet (0.02 µg selenium/g diet) (2). Increasing selenium supplementation to 0.1 µg/g–2 µg/g, as either selenite or selenomethionine, does not lead to further changes in tHcy homeostasis (3,4).
It should also be noted that investigating the relationship between dietary selenium and tHcy without considering other dietary components may lead to erroneous conclusions. For example, selenium deficiency has a more profound effect on tHcy in rats fed a folate-deficient diet than in those fed a folate-adequate diet (5). Similarly, it is possible that other dietary factors such as methionine, vitamins B-6 and B-12, choline and/or zinc may also affect this relationship. For this reason, we believe that investigating the relationship between dietary selenium and tHcy, particularly in clinical studies, requires the consideration of these modifying variables. Examining such interactions may prove exceedingly important to understanding the influence of selenium on tHcy.
Manuscript received 18 March 2003.
LITERATURE CITED
1. Venn, B. J., Grant, A. M., Thomson, C. & D & Green, T. J. (2003) Selenium supplements do not increase plasma total homocysteine concentrations in men and women. J. Nutr. 133:418-420.
2. Uthus, E. O, Yokoi, K. & Davis, C. D. (2002) Selenium deficiency in Fischer-344 rats decreased plasma and tissue homocysteine concentrations and alters plasma homocysteine and cysteine redox status. J. Nutr. 132:1122-1128.
3. Davis, C. D., Uthus, E. O. & Finley, J. W. (2000) Dietary selenium and arsenic affect DNA methylation in vitro in Caco-2 cells and in vivo in rat liver and colon. J. Nutr. 130:2903-2909.
4. Davis, C. D. & Uthus, E. O. (2002) Dietary selenite and azadeoxycytidine treatments affect dimethylhydrazine-induced aberrant crypt formation in rat colon and DNA methylation in HT-29 cells. J. Nutr. 132:292-297.
5. Davis, C. D. & Uthus, E. O. (2003) Dietary selenium (Se) and folate affect dimethylhydrazine (DMH)-induced aberrant crypt formation, global DNA methylation and one-carbon metabolism in rats. FASEB 17:A1371.
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