Food Iron Absorption Measured by an Extrinsic Tag

Cook, James D.; Layrisse, Miguel; Martínez-Torres, Carlos; Walker, Richard B.; Monsen, Elaine R; Finch, Clement A.

doi:10.1172/jci106875

Cited by 304 publications

(110 citation statements)

References 26 publications

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“…By administering the dose of iron label over the course of 3 days, we achieved a contribution of the extrinsic tag of 31% to the total meal iron in the spinach meal and 61% in the kale meals (due to the lower iron content). The extrinsic tag has been shown to be a valid approach up to a level of 20% for dietary iron absorption studies using complete meals due to rapid isotopic exchange and the formation of a common nonhaem iron pool, with a suggestion that higher levels are also acceptable (Cook et al, 1972;Bjorn-Rasmussen et al, 1973). Isotopically labelled 57 FeSO 4 and 58 FeSO 4 were prepared from isotopically enriched elemental iron (Chemgas, Boulogne, France) dissolved in dilute sulphuric acid.…”

Section: Methodsmentioning

confidence: 99%

Oxalic acid does not influence nonhaem iron absorption in humans: a comparison of kale and spinach meals

et al. 2007

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Objective: To evaluate the influence of oxalic acid (OA) on nonhaem iron absorption in humans. Design: Two randomized crossover stable iron isotope absorption studies. Setting: Zurich, Switzerland. Subjects: Sixteen apparently healthy women (18-45 years, o60 kg body weight), recruited by poster advertizing from the staff and student populations of the ETH, University and University Hospital of Zurich, Switzerland. Thirteen subjects completed both studies. Methods: Iron absorption was measured based on erythrocyte incorporation of 57 Fe or 58 Fe 14 days after the administration of labelled meals. In study I, test meals consisted of two wheat bread rolls (100 g) and either 150 g spinach with a native OA content of 1.27 g (reference meal) or 150 g kale with a native OA content of 0.01 g. In study II, 150 g kale given with a potassium oxalate drink to obtain a total OA content of 1.27 g was compared to the spinach meal. Results: After normalization for the spinach reference meal absorption, geometric mean iron absorption from wheat bread rolls with kale (10.7%) did not differ significantly from wheat rolls with kale plus 1.26 g OA added as potassium oxalate (11.5%, P ¼ 0.86). Spinach was significantly higher in calcium and polyphenols than kale and absorption from the spinach meal was 24% lower compared to the kale meal without added OA, but the difference did not reach statistical significance (P40.16). Conclusion: Potassium oxalate did not influence iron absorption in humans from a kale meal and our findings strongly suggest that OA in fruits and vegetables is of minor relevance in iron nutrition.

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Section: Methodsmentioning

confidence: 99%

Oxalic acid does not influence nonhaem iron absorption in humans: a comparison of kale and spinach meals

et al. 2007

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“…The heme and nonheme iron pools of the standard meal were tagged extrinsically (6)(7)(8) as follows. The heme iron fraction was labeled by adding 0.6 mg iron and 3 uCi radioactivity as "5Fe-labeled hemoglobin to the ground beef immediately before the meal was served.…”

Section: Methodsmentioning

confidence: 99%

“…The heme iron fraction was labeled by adding 0.6 mg iron and 3 uCi radioactivity as "5Fe-labeled hemoglobin to the ground beef immediately before the meal was served. Radioactive hemoglobin was prepared in a pathogen-free rab- 7.4. The mucosal cell preparation was kept on crushed ice throughout the processing procedure.…”

Section: Methodsmentioning

confidence: 99%

Duodenal iron proteins in idiopathic hemochromatosis.

Whittaker¹,

Skikne²,

Covell³

et al. 1989

J. Clin. Invest.

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This study was undertaken to assess the relationship between iron absorption and the concentration of duodenal iron proteins in normal subjects and patients with idiopathic hemochromatosis (IH). Biopsies were obtained endoscopically from the duodenum in 17 normal subjects, 3 of whom were mildly iron deficient, and 7 patients with untreated IH. The absorption of both heme and nonheme iron was increased in IH despite a 20-fold elevation in serum ferritin. Immunoassays using MAb were used to measure transferrin, H-rich ferritin, and L-rich ferritin in mucosal samples. Mucosal transferrin concentrations in normal subjects did not correlate with either iron status or iron absorption, indicating that mucosal transferrin plays no physiological role in iron absorption. Mucosal transferrin was significantly lower in IH, presumably because of a decrease in mucosal transferrin receptors. Mucosal H and L ferritin concentrations were directly related to body iron stores and inversely related to iron absorption in normal subjects. In IFH, mucosal H and L ferritin failed to increase in parallel with the serum ferritin, but were appropriate for the level of iron absorption. The relationship of mucosal H/L ferritin in IH did not differ from that observed in normal subjects. Our findings indicate that the major abnormality in duodenal iron proteins in IH is a parallel decrease in the concentration of H-and L-rich ferritin. It is-not evident whether this is the result or the cause of the absorptive abnormality.

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“…This caveat is not evident in traditional radioiron bioavailability studies that utilize an extrinsic tag or tracerFa minute amount of added radioactive ironFthat is assumed to enter the common pool and behave identically to the dietary soluble nonheme iron therein. This has been well demonstrated for the native iron in many foodstuffs and soluble iron salts such as ferrous sulfate (Layrisse et al, 1969(Layrisse et al, , 1973Bjorn-Rasmussen et al, 1972, 1974Cook et al, 1972).…”

Section: Introductionmentioning

confidence: 82%

Bioavailability of elemental iron powder in white wheat bread

et al. 2004

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Objective: Iron fortification of wheat flour is widely used. In most cases, elemental iron powders are utilized as fortificants due to their lower cost and few, if any, sensory problems. However, their bioavailability is unknown. We aimed to measure the bioavailability of H 2 -reduced elemental iron powder in white wheat bread made from 72% extraction flour. Design: A stable isotope of H 2 -reduced iron powder (mean particle size 15 mm) was used as fortificant in bread prepared from unfortified wheat flour. In all, 12 5-to 7-y-old children were fed bread with 4 mg of H 2 -reduced 58 Fe /100 g of flour. The next day 57 Fe ascorbate was given as reference dose. After 14 days, erythrocytes were analyzed for isotopic enrichment using mass spectrometry. Results: When normalized to 40% absorption of the reference dose, the geometric mean (7range of 1 s.d.) bioavailability of reduced 58 Fe in wheat bread rolls was 6.5% (3.7-11.8). Conclusions: When compared to previous radioiron studies of ferrous sulfate showing 10% absorption from an identical meal in adult women, the relative bioavailability can be estimated at about 65%. However, the bioavailability of this smaller particle size 58 Fe (15 mm) is likely to be higher than that of commercial iron powder (45 mm) although the precise difference cannot be ascertained with current methods. Thus, the bioavailability of commercial elemental iron powders currently used in fortification programs is likely to be substantially lower than that of ferrous sulfate.

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Food Iron Absorption Measured by an Extrinsic Tag

Cited by 304 publications

References 26 publications

Oxalic acid does not influence nonhaem iron absorption in humans: a comparison of kale and spinach meals

Oxalic acid does not influence nonhaem iron absorption in humans: a comparison of kale and spinach meals

Duodenal iron proteins in idiopathic hemochromatosis.

Bioavailability of elemental iron powder in white wheat bread

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