![[Feedback]](/icons/banner/feedbackACT.gif){kind=icon}
![[For Subscribers]](/icons/banner/subscriberACT.gif){kind=icon}
![[Archive]](/icons/banner/archiveACT.gif){kind=icon}
![[Search]](/icons/banner/searchACT.gif){kind=icon}
![[Contents]](/icons/banner/tocACT.gif){kind=icon}
|
|
|
|
|
||
Department of Food Science, Cornell University, Ithaca, NY 14853, and * U.S. Plant, Soil and Nutrition Laboratory, USDA/ARS, Ithaca, NY 14853
2To whom correspondence should be addressed. E-mail: ddm2{at}cornell.edu.
 |
ABSTRACT |
|---|
 TOP ABSTRACT MATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
KEY WORDS: • iron absorption • downregulation • NaFeEDTA • ferrous sulfate • rats
NaFeEDTA, an iron chelate, was approved by the Joint Expert Committee on Food Additives (JECFA) of FAO/WHO for use in intervention programs in the last decade (1,2). The approval was supported by a number of human studies that demonstrated the superior bioavailability of NaFeEDTA when added to a variety of foods and meals (3–8). Because of its exceptional stability in long shelf-life foods (9) and solubility in low to near neutral pH aqueous environments (10), NaFeEDTA is particularly well suited for fortifying flours, cereals, legumes, and other staple crops (11). These plant-based foods are the primary dietary staples in developing countries, where meat consumption is usually low (12), and where iron deficiency anemia is usually more prevalent than in developed countries (13). Iron fortification can be an effective strategy in reducing the prevalence of iron deficiency, provided that the iron is in a bioavailable form when it reaches the proximal small intestine of the consumer. Because many plant-based foods are good sources of phytates and phenolic compounds, both of which are potent iron absorption inhibitors (14–16), the advantage of NaFeEDTA as an iron fortificant becomes more obvious because the bioavailability of NaFeEDTA is less affected by iron absorption inhibitors compared with other fortificants such as ferrous sulfate (7,17). Results from field studies tend to validate NaFeEDTA as an effective fortificant for alleviating problems of iron deficiency (18–22).
EDTA binds ferric and ferrous iron with higher affinity than other ligands such as citric acid and phenolic compounds (23). Others have suggested that the metal iron dissociates from the EDTA ligand within the lumen of the gastrointestinal tract prior to mucosal uptake (24,25), hence, the premise that iron absorption from NaFeEDTA is regulated similarly as with iron salts. This view is plausible based on the results from a pig study that showed there was more soluble 14C than 59Fe in the feces of pigs fed meals containing NaFeEDTA doubly labeled with 59Fe and 14C (26). Nonetheless, these results from pigs do not eliminate the possibilities that some amount of the FeEDTA complexes could be absorbed intact or absorbed through a different pathway (e.g., paracellular route), rather than the normal, highly regulated transcellular pathways for ionic iron.
Although analyses so far on the safety and the toxicology of NaFeEDTA (25,27) have suggested that its use in food poses no adverse health effects, NaFeEDTA is not yet approved by the FDA for food use in the United States. A comprehensive rat study showed that the disposition, accumulation, and toxicity of iron fed as NaFeEDTA are essentially identical to those of ferrous sulfate (28). There remains a concern that the broad use of NaFeEDTA as a food fortificant could lead to, or could exacerbate, iron overload in some sectors of populations, especially those individuals with adequate body iron stores. Iron absorption is inversely related to iron status (29–33). This regulation occurs with both heme and nonheme iron, but there is a greater response with nonheme iron (34). Therefore, it is imperative to evaluate whether iron absorption from an iron chelate such as NaFeEDTA is effectively downregulated in iron-replete subjects, particularly in comparison with an iron salt such as ferrous sulfate.
The objective of this study was to compare downregulation of iron absorption from ferrous sulfate and NaFeEDTA in intact rats with elevated iron status.
|
MATERIALS AND METHODS |
|---|
|
TOPABSTRACTMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
Diets. All test diets for the iron loading and absorption assessment periods were based on a commercial iron-deficient AIN-93G purified rodent diet (Dyets #115072, Dyets) (35) and were prepared by adding different forms and concentrations of iron to this iron-deficient AIN-93G diet (Table 1). The iron sources were incorporated into the diet by using a mechanical mixer (Hobart). The iron-deficient AIN-93G diet was found to contain 2 mg Fe per 1 kg diet, analyzed by the method described by Kosse et al. (36).
|
Animals. Weanling male Sprague-Dawley rats with a mean body weight of 40 g were purchased from Charles River. They were housed individually in a temperature-controlled room in stainless-steel cages, on a 12-h dark–light cycle. Upon arrival at the housing facility, rats were fed a basal diet (containing 35 mg Fe as ferrous sulfate per 1 kg diet) for 7 d to acclimate them to the housing and the feeding. This concentration of iron is sufficient for growth and for achieving maximum hemoglobin concentration (37). All rats were given free access to food and deionized water during the acclimation period.
Experimental protocols. On day 1 of the experiment, rats, blocked by their body weights, were divided into 4 groups of 9 rats. While 2 basal groups remained on the basal diet, the 2 iron-loaded groups received a diet containing 30,000 mg of elemental iron per 1 kg diet to induce iron loading (38). All rats had free access to food and deionized water during the iron-loading period (days 1–29). The rats were food deprived overnight prior to 59Fe dosing.
On day 30, 1 basal group and 1 iron-loaded group were treated with a dose of the 59FeSO4 meal, whereas the remaining groups were treated with a dose of the Na59FeEDTA meal. The meals were offered ad libitum for 3 h and any spillage was collected. After the 3-h treatment period, each rat was assayed for 59Fe activity in a whole-body gamma spectrometer (Tobor Large Sample Gamma Counter, Nuclear Chicago) to accurately determine the activity of the initial dose. Rats were then returned to their respective diets (unlabeled diets containing either ferrous sulfate or NaFeEDTA) and were assayed, subsequently, for whole-body 59Fe activity at 24-h intervals during the absorption assessment period (days 31–40).
On day 41, rats were killed and blood, liver, spleen, and kidney samples were collected. Rats were first anesthetized with CO2, and blood samples were obtained by cardiac puncture. Immediately after blood sampling, the rats were killed with an overdose of CO2. Liver, spleen, and kidneys were removed and accurately weighed portions were analyzed for nonheme iron concentrations.
Rats were observed daily during the whole study for signs of abnormalities. The body weights of the rats were recorded before and after the iron-loading period, and before they were killed. Animal care procedures and experimental protocols were approved by the Institutional Animal Care and Use Committees of both Cornell University and the U.S. Plant, Soil and Nutrition Laboratory.
Calculations of iron absorption. The retention of 59Fe in rats at the end of each 24-h interval was determined and expressed as a percentage of the initial dose. Retention data, plotted as a function of elapsed time after treatment, could be described by exponential functions (39), and the functions were used to calculate iron absorption as previously described (39–44). Briefly, the percentage of absorbed 59Fe was estimated by extrapolating the terminal component of the retention curve to time 0.
Tissue analyses. Nonheme iron concentrations in liver, spleen, and kidney samples were determined by the colorimetric method described by Schricker et al. (45), with modifications reported by Rhee and Ziprin (46) for minimizing the breakdown of heme pigments into nonheme iron. Results were expressed as µmol nonheme Fe per 1 g tissue (wet weight) and were used as indices of rat iron status. The hemoglobin concentrations of the collected blood samples were determined by the cyanmethemoglobin method (47).
Statistical analysis. All statistical analyses were done by using Minitab (Minitab). The effect of iron loading on nonheme iron concentrations in rat tissues was analyzed by one-way ANOVA, followed by Fisher’s least-significant difference procedures. Differences in percentage of iron absorption in rats were analyzed by two-way ANOVA to determine the effects of iron status (basal or iron loaded) and iron source (ferrous sulfate or NaFeEDTA) and their interaction. A P-value of <0.05 was considered significant.
|
RESULTS |
|---|
|
TOPABSTRACTMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
Blood hemoglobin concentration. The mean blood hemoglobin concentration of rats was 179.7 g/L. There were no significant differences among the 4 groups.
Tissue nonheme iron concentration. Nonheme iron concentrations in liver, spleen, and kidney were significantly higher in the 2 iron-loaded groups than in the 2 basal groups (Fig. 1). In particular, liver nonheme iron concentration in iron-loaded rats was about 9-fold higher than in basal rats, whereas the differences were only about 4-fold for spleen and less than 2-fold for kidney. In addition, liver and spleen nonheme iron concentrations of iron-loaded rats dosed with ferrous sulfate during the iron absorption assessment period were slightly higher than those dosed with NaFeEDTA, but there were no differences between the 2 basal groups. For kidney nonheme iron concentration, there were no differences between the 2 iron-loaded groups, but basal rats dosed with ferrous sulfate had higher kidney nonheme iron concentration than those with NaFeEDTA.
|
|
Based on the retention data, iron absorption from ferrous sulfate and NaFeEDTA in rats with different iron status was determined (Fig. 3). In basal rats, the group fed ferrous sulfate (64.7%) showed higher percentage of iron absorption than the group fed NaFeEDTA (49.4%), suggesting that ferrous sulfate is more bioavailable than NaFeEDTA to these rats. In iron-loaded rats, iron absorption was similar between the groups fed either ferrous sulfate (12.8%) or NaFeEDTA (10.2%). The reductions in percentage of iron absorption from both iron sources, as a result of iron loading, were substantial, as well as comparable (about –80% for both iron sources, Fig. 3). Iron absorption from NaFeEDTA and ferrous sulfate was downregulated similarly in rats with elevated iron status.
|
|
DISCUSSION |
|---|
|
TOPABSTRACTMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
When fed different levels of dietary iron, rats accumulate variable amounts of iron in body tissues, including liver, heart, kidney, spleen, etc. (28,38,48). As shown in the present study, iron-loaded rats accumulated a markedly higher amount of liver nonheme iron than basal rats, an indication that iron-loaded rats had elevated iron status; liver nonheme-iron concentration can be used as an index of iron loading in rats (49). Our results also showed that spleen and kidney in iron-loaded rats had higher nonheme iron concentrations. Nevertheless, spleen and kidney are less sensitive to iron loading when compared with liver.
The rat liver nonheme-iron concentrations shown in our results are substantially lower than those reported by Appel et al. (28), when rats were fed similar diets (35 mg Fe as ferrous sulfate per 1 kg diet) for approximately the same time period. Although the age of the rats used in their study was about 1 wk older and this could contribute to higher liver nonheme iron concentrations, the discrepancy may be better explained by the differences in the methods used for liver analyses. The procedures (48,50) followed by Appel et al. did not include the use of NaNO2, which prevents the release of heme iron as nonheme iron upon heating the tissue samples (51). It has been shown that determining nonheme iron concentrations without the nitrite treatment could lead to a 40% overestimation in various meat samples (46).
Comparisons of rat and human absorption trials show that rats absorb a higher percentage of iron from foods than humans (41–42,49,52–54). Therefore, our results should be interpreted qualitatively and on a relative comparison basis. Although it is unlikely that percentage of iron absorption and hence the magnitude of downregulation would be the same in humans and rats, studies have shown that rats do regulate iron absorption in response to changes in iron status (42,55). Our results suggest that iron absorption from NaFeEDTA, when compared with ferrous sulfate, is downregulated to a similar extent in iron-overload conditions. Therefore, NaFeEDTA should be no more likely than ferrous sulfate to exacerbate iron overload in subjects with adequate body iron stores.
The FDA has yet to approve the use of NaFeEDTA in staple foods, partly because of the concern over possible adverse effects of excessive levels of EDTA in the diet. An estimate in 1993 suggested that the dietary levels of EDTA in the United States were substantially lower than previously thought (27), and this estimation was confirmed by a more recent study (25). The estimated daily intakes of EDTA at the 90th percentile from current plus intended uses are 1.15 and 2.06 mg EDTA/(kg body wt · d) for the overall U.S. population and for children aged 1–6 y old, respectively (25), corresponding to 46 and 82% of the acceptable daily intake (ADI) of 2.50 mg EDTA/(kg body wt · d) established by the JECFA, respectively. These estimations are based on the assumption that NaFeEDTA will be used at maximum intended concentrations in all brands and all product lines of ready-to-eat cereals, toaster pastries, breakfast bars, and granola bars, as well as in all currently approved EDTA applications. (Disodium EDTA and calcium disodium EDTA are currently approved for use in some canned foods and beverages.) Although the majority of the population is not at risk of consuming too much EDTA, the possibility that the ADI will be exceeded in some young children is not negligible if NaFeEDTA is allowed in infant foods. It should be noted that the JECFA stipulates the use of NaFeEDTA in intervention programs at the level of 0.2 mg Fe/(kg body wt · d) (2). This level of NaFeEDTA intake would then constitute about 1 mg EDTA/(kg body wt · d).
Another safety concern of NaFeEDTA is that the consumption of NaFeEDTA may inhibit the absorption of other minerals, such as zinc, calcium, and manganese, because EDTA is a strong metal chelating agent. Nonetheless, Davidsson et al. (56) showed that zinc absorption was greater from NaFeEDTA-fortified bread rolls than from those fortified with ferrous sulfate, whereas calcium absorption was essentially unchanged in 10 healthy women. Manganese absorption was also unaffected in 10 human subjects after consuming a weaning cereal meal fortified with either NaFeEDTA or ferrous sulfate (57). These results suggest that the use of NaFeEDTA for iron fortification has no detrimental effects on zinc, calcium, or manganese absorption in humans. In addition, disodium EDTA has been shown to have no effect on lead absorption in mice (58). Disodium EDTA has also been shown to chelate cadmium and reduce mortality and tissue damage induced by acute oral cadmium intoxication in mice (59).
Appel et al. (28) reported that iron accumulated in liver, spleen, and kidney in a dose-dependent manner in rats fed diets containing either ferrous sulfate or NaFeEDTA for 31 and 61 d. Feeding iron from either source up to about 11 mg/(kg body wt · d) did not result in excess tissue iron or any other toxicologically significant effects, suggesting that prolonged exposure to a NaFeEDTA-fortified diet is not different from a FeSO4-fortified diet. In the present study, rats were fed a high elemental iron diet to achieve iron loading. Subsequent iron absorption from both ferrous sulfate and NaFeEDTA was effectively downregulated. These results, taken together, appear to support the use of NaFeEDTA as an iron fortificant. However, studies on postabsorptive distribution of iron in rat tissues suggest that EDTA promotes marked urinary excretion of iron and elevates iron accumulation in kidney (60). The mechanisms of absorption and excretion of iron from NaFeEDTA should be carefully examined before NaFeEDTA is used in national fortification programs.
In conclusion, iron absorption from NaFeEDTA is downregulated effectively in iron-loaded rats, and NaFeEDTA is no more likely than ferrous sulfate to exacerbate iron overload. Since NaFeEDTA is known to have better bioavailability than ferrous sulfate in the presence of iron absorption inhibitors, further investigation of whether rats can adapt to NaFeEDTA-fortified diets containing different levels of inhibitors is warranted.
|
ACKNOWLEDGMENTS |
|---|
|
FOOTNOTES |
|---|
Manuscript received 17 March 2004. Initial review completed 2 May 2004. Revision accepted 14 June 2004.
|
LITERATURE CITED |
|---|
|
TOPABSTRACTMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
1. FAO/WHO (1993) Evaluation of Certain Food Additives and Contaminants: 41st Report of the Joint FAO/WHO Expert Committee on Food Additives. Technical Report Series 837 1993 WHO Geneva, Switzerland.
2. FAO/WHO (2000) Evaluation of Certain Food Additives and Contaminants: 53rd Report of the Joint FAO/WHO Expert Committee on Food Additives. Technical Report Series 896 2000 WHO Geneva, Switzerland.
3. Layrisse, M. & Martinez-Torres, C. (1977) Fe(III)-EDTA complex as iron fortification. Am. J. Clin. Nutr. 30:1166-1174.
4. Viteri, F. E., Garcia-Ibanez, R. & Torun, B. (1978) Sodium iron NaFeEDTA as an iron fortification compound in Central America. Absorption studies. Am. J. Clin. Nutr. 31:961-971.
5. Martinez-Torres, C., Romano, E. L., Renzi, M. & Layrisse, M. (1979) Fe(III)-EDTA complex as iron fortification. Further studies. Am. J. Clin. Nutr. 32:809-816.
6. MacPhail, A. P., Bothwell, T. H., Torrance, J. D., Derman, D. P., Bezwoda, W. R., Charlton, R. W. & Mayet, F. (1981) Factors affecting the absorption of iron from Fe(III)EDTA. Br. J. Nutr. 45:215-227.[Medline]
7. Hurrell, R. F., Reddy, M. B., Burri, J. & Cook, J. D. (2000) An evaluation of EDTA compounds for iron fortification of cereal-based foods. Br. J. Nutr. 84:903-910.[Medline]
8. Mendoza, C., Viteri, F. E., Lonnerdal, B., Raboy, V., Young, K. A. & Brown, K. H. (2001) Absorption of iron from unmodified maize and genetically altered, low-phytate maize fortified with ferrous sulfate or sodium iron EDTA. Am. J. Clin. Nutr. 73:80-85.
9. Bovell-Benjamin, A., Allen, L., Frankel, E. & Guinard, J. (1999) Sensory quality and lipid oxidation of maize porridge as affected by iron amino acid chelates and EDTA. J. Food Sci. 54:371-376.
10. Garcia-Casal, M. N. & Layrisse, M. (2001) The effect of change in pH on the solubility of iron bis-glycinate chelate and other iron compounds. Arch. Latinoam. Nutr. 51:35-36.[Medline]
11. International Nutritional Anemia Consultative Group (INACG) (1993) Iron EDTA for Food Fortification 1993 ILSI Press Washington, DC.
12. FAOSTAT [Online] () Food and Agriculture Organization Statistical Databases. http://apps.fao.org [accessed Feb. 12, 2004] .
13. Yip, R. (2001) Iron. Bowman, B. A. Russell, R. M. eds. Present Knowledge in Nutrition 2001:311-328 ILSI Press Washington, DC. .
14. Brune, M., Rossander, L. & Hallberg, L. (1989) Iron absorption and phenolic compounds: importance of different phenolic structures. Eur. J. Clin. Nutr. 43:547-557.[Medline]
15. Hallberg, L., Brune, M. & Rossander, L. (1989) Iron absorption in man: ascorbic acid and dose-dependent inhibition by phytate. Am. J. Clin. Nutr. 49:140-144.
16. Sandberg, A. S., Brune, M., Carlsson, N. G., Hallberg, L., Skoglund, E. & Rossander-Hulthen, L. (1999) Inositol phosphates with different numbers of phosphate groups influence iron absorption in humans. Am. J. Clin. Nutr. 70:240-246.
17. Layrisse, M., Garcia-Casal, M. N., Solano, L., Baron, M. A., Arguello, F., Llovera, D., Ramirez, J., Leets, I. & Tropper, E. (2000) Iron bioavailability in humans from breakfasts enriched with iron bis-glycine chelate, phytates and polyphenols. J. Nutr. 130:2195-2199.
18. Garby, L. & Areekul, S. (1974) Iron supplementation in Thai fish-sauce. Ann. Trop. Med. Parasitol. 68:467-476.[Medline]
19. Ballot, D. E., MacPhail, A. P., Bothwell, T. H., Gillooly, M. & Mayet, F. G. (1989) Fortification of curry powder with NaFe(III)EDTA in an iron-deficient population: report of a controlled iron-fortification trial. Am. J. Clin. Nutr. 49:162-169.
20. Viteri, F. E., Alvarez, E., Batres, R., Torun, B., Pineda, O., Mejia, L. A. & Sylvi, J. (1995) Fortification of sugar with iron sodium ethylenediaminotetraacetate (FeNaEDTA) improves iron status in semirural Guatemalan populations. Am. J. Clin. Nutr. 61:1153-1163.
21. Huo, J., Sun, J., Miao, H., Yu, B., Yang, T., Liu, Z., Lu, C., Chen, J. & Zhang, D., et al (2002) Therapeutic effects of NaFeEDTA-fortified soy sauce in anaemic children in China. Asia Pac. J. Clin. Nutr. 11:123-127.[Medline]
22. Thuy, P. V., Berger, J., Daivdsson, L., Khan, N. C., Lam, N. T., Cook, J. D., Hurrell, R. F. & Koi, H. H. (2003) Regular consumption of NaFeEDTA-fortified fish sauce improves iron status and reduces the prevalence of anemia in anemic Vietnamese women. Am. J. Clin. Nutr. 78:284-290.
23. South, P. K. & Miller, D. D. (1998) Iron binding by tannic acid: effects of selected ligands. Food Chem. 63:167-172.
24. Hurrell, R. F. (1997) Preventing iron deficiency through food fortification. Nutr. Rev. 55:210-222.[Medline]
25. Heimbach, J., Rieth, S., Mohamedshah, F., Slesinski, R., Samual-Fernando, P., Sheehan, T., Dickmann, R. & Borzelleca, J. (2000) Safety assessment of iron EDTA [sodium iron (Fe3+) ethylenediaminetetraacetic acid]: summary of toxicological, fortification and exposure data. Food Chem. Toxicol. 38:99-111.[Medline]
26. Candela, E., Camacho, M. V., Martinez-Torres, C., Perdomo, J., Mazzarri, G., Acurero, G. & Layrisse, M. (1984) Iron absorption by humans and swine from Fe(III)-EDTA. Further studies. J. Nutr. 114:2204-2211.
27. Whittaker, P., Vanderveen, J. E., DiNovi, M. J., Kuznesof, P. M. & Dunkel, V. C. (1993) Toxicological profile, current use and regulatory issues of EDTA compound for assessing potential use of sodium iron EDTA for food fortification. Regul. Toxicol. Pharmacol. 18:419-427.[Medline]
28. Appel, M. J., Kuper, C. F. & Woutersen, R. A. (2001) Disposition, accumulation and toxicity of iron fed as iron (II) sulfate or as sodium iron EDTA in rats. Food Chem. Toxicol. 39:261-269.[Medline]
29. Magnusson, B., Bjorn-Rasmussen, E., Hallberg, L. & Rossander, L. (1981) Iron absorption in relation to iron status. Scand. J. Haemat. 27:201-208.[Medline]
30. Taylor, P., Martinez-Torres, C., Leets, I., Ramirez, J., Garcia-Casal, M. N. & Layrisse, M. (1988) Relationships among iron absorption, percent saturation of plasma transferrin and serum ferritin concentration in humans. J. Nutr. 118:1110-1115.
31. Lynch, S. R., Skikne, B. S. & Cook, J. D. (1989) Food iron absorption in idiopathic hemochromatosis. Blood 74:2187-2193.
32. Flanagan, P. R. (1989) Mechanisms and regulation of intestinal uptake and transfer of iron. Acta Paediatr. Scand. 361:21S-30S.
33. Hallberg, L., Hulten, L. & Gramatkovski, E. (1997) Iron absorption from the whole diet in men: how effective is the regulation of iron absorption?. Am. J. Clin. Nutr. 66:347-356.
34. Cook, J. D. (1990) Adaptation in iron metabolism. Am. J. Clin. Nutr. 51:301-308.
35. Reeves, P. G., Nielsen, F. H. & Fahey, G. C., Jr (1993) AIN-93 purified diets for laboratory rodents: final report of the American Institute of Nutrition Ad Hoc Writing Committee on the Reformulation of the AIN-76A Rodent Diet. J. Nutr. 123:1939-1951.
36. Kosse, J. S., Yeung, A. C., Gil, A. I. & Miller, D. D. (2001) A rapid method for iron determination in fortified foods. Food Chem. 75:371-376.
37. National Research Council (NRC) (1995) Nutrient Requirements of Laboratory Animals 1995 The National Academies Press Washington, DC.
38. Park, C. H., Bacon, B. R., Brittenham, G. M. & Tavill, A. S. (1987) Pathology of dietary carbonyl iron overload in rats. Lab. Invest. 57:555-563.[Medline]
39. Van Campen, D. & House, W. A. (1974) Effect of a low protein diet on retention of an oral dose of 65Zn and on tissue concentrations of zinc iron and copper in rats. J. Nutr. 104:84-90.
40. Welch, R. M., House, W. A. & Allaway, W. H. (1974) Availability of zinc from pea seeds to rats. J. Nutr. 104:733-740.
41. Welch, R. M. & Van Campen, D. (1975) Iron availability to rats from soybeans. J. Nutr. 105:253-256.
42. Schricker, B. R., Miller, D. D. & Van Campen, D. (1983) Effects of iron status and soy protein on iron absorption by rats. J. Nutr. 113:996-1001.
43. South, P. K., House, W. A. & Miller, D. D. (1997) Tea consumption does not affect iron absorption in rats unless tea and iron are consumed together. Nutr. Res. 17:1303-1310.
44. Welch, R. M., House, W. A., Beebe, S. & Cheng, Z. (2000) Genetic selection for enhanced bioavailable levels of iron in bean (Phaseolus vulgaris L.) seeds. J. Agric. Food Chem. 48:3576-3580.[Medline]
45. Schricker, B. R., Miller, D. D. & Stouffer, J. R. (1982) Measurement and content of nonheme and total iron in muscle. J. Food Sci. 47:740-743.
46. Rhee, K. S. & Ziprin, Y. A. (1987) Modification of the Schricker nonheme iron method to minimize pigment effects for red meats. J. Food Sci. 52:1174-1176.
47. Davidsohn, I. & Nelson, D. A. (1974) The blood. Davidsohn, I. Henry, J. B. eds. Clinical Diagnosis by Laboratory Methods 1974:100-310 W. B. Saunders Philadelphia, PA. .
48. Whittaker, P., Hines, F. A., Robl, M. G. & Dunkel, V. C. (1996) Histopathological evaluation of liver, pancreas, spleen, and heart from iron-overloaded Sprague-Dawley rats. Toxicol. Pathol. 24:558-563.
49. Reddy, M. B. & Cook, J. D. (1989) Assessment of dietary determinants of nonheme-iron absorption in humans and rats. Am. J. Clin. Nutr. 54:723-728.
50. Whittaker, P., Dunkel, V. C., Bucci, T. J., Kusewitt, D. F., Thurman, J. D., Warbritton, A. & Wolff, G. L. (1997) Genome-linked toxic responses to dietary iron overload. Toxicol. Pathol. 25:556-564.
51. Morrissey, P. A. & Tichivangana, J. Z. (1985) The antioxidant activities of nitrite and nitrosylmyoglobin in cooked meats. Meat Sci. 14:175-190.
52. Cook, J. D., Morck, T. A. & Lynch, S. R. (1981) The inhibitory effect of soy products on nonheme iron absorption in man. Am. J. Clin. Nutr. 34:2622-2629.
53. Forbes, A. L., Adams, C. E., Arnaud, M. J., Chichester, C. O., Cook, J. D., Harrison, B. N., Hurrell, R. F., Kahn, S. G. & Morris, E. R., et al (1989) Comparison of in vitro, animal, and clinical determinations of iron bioavailability: International Nutritional Anemia Consultative Group Task Force report on iron bioavailability. Am. J. Clin. Nutr. 49:225-238.
54. Wienk, K.J.H., Marx, J.J.M. & Beynen, A. C. (1999) The concept of iron bioavailability and its assessment. Eur. J. Nutr. 38:51-75.[Medline]
55. Ward, R. J., Smith, T., Henderson, G. M. & Peters, T. J. (1991) Investigation of the aetiology of haemosiderosis in the starling (Sturnus vulgaris). Avian Pathol. 20:225-232.[Medline]
56. Davidsson, L., Kastenmayer, P. & Hurrell, R. F. (1994) Sodium iron EDTA [NaFe(III)EDTA] as a food fortificant: the effect on the absorption and retention of zinc and calcium in women. Am. J. Clin. Nutr. 60:231-237.
57. Davidsson, L., Almgren, A. & Hurrell, R. F. (1998) Sodium iron EDTA [NaFe(III)EDTA] as a food fortificant does not influence absorption and urinary excretion of manganese in healthy adults. J. Nutr. 128:1139-1143.
58. Garber, B. T. & Wei, E. (1974) Influence of dietary factors on the gastrointestinal absorption of lead. Toxicol. Appl. Pharmacol. 27:685-691.[Medline]
59. Andersen, O., Nielsen, J. O. & Svendsen, P. (1988) Oral cadmium chloride intoxication in mice: effects of chelation. Toxicology 52:65-79.[Medline]
60. Hopping, J. M. & Ruliffson, W. S. (1963) Effects of chelating agents on radioiron absorption and distribution in rats in vivo. Am. J. Physiol. 205:885-889.
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
