Iron absorption from ferrous bisglycinate and ferric trisglycinate in whole maize is regulated by iron status

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Abstract
Background: There is a need to determine whether iron absorption from iron amino acid chelates is protected from inhibition by dietary phytate and regulated normally by iron status. Objective: The objective of this study was to compare iron absorption from ferrous sulfate, ferrous bisglycinate, and ferric trisglycinate in whole-maize meal; to determine whether iron from ferrous bisglycinate and ferrous sulfate exchanges in the intestinal pool; and to assess iron absorption from ferrous bisglycinate and ferric trisglycinate over a range of iron statuses. Design: In study 1A, 10 iron-sufficient men consumed ferrous sulfate–fortified whole-maize meal porridge equilibrated with 59Fe-sulfate on day 1 and 55Fe-bisglycinate on day 2. In study 1B, these volunteers consumed ferrous sulfate–fortified porridge equilibrated with 59Fe-sulfate and 55Fe-bisglycinate simultaneously. In studies 2A and 2B, iron absorption from 3 mg Fe as 59Fe-ascorbate, 55Fe-bisglycinate, or 59Fe-trisglycinate in water and in porridge was compared in 23 subjects with a range of iron statuses. Iron absorption was determined from blood radioactivity on day 16. Results: In study 1A, geometric mean iron absorption from ferrous bisglycinate was 6.0% (range: 2.6–13.6%), 4 times higher than that from ferrous sulfate (1.7%; range: 1.0–3.3%; P < 0.05). In study 1B, absorption from neither source was different from that in study 1A. In studies 2A and 2B, absorption from all sources was strongly inversely related to serum ferritin, with geometric means of 32.5% (iron ascorbate), 9.1% (bisglycinate), and 15.3% (trisglycinate). Iron from ferric trisglycinate was poorly absorbed (2.3%; range: 0.5–9.2%) from maize. Conclusion: In whole-maize meal, iron from ferrous bisglycinate is better absorbed than is iron from ferrous sulfate and does not exchange with iron from maize or ferrous sulfate in the intestinal pool. Absorption of iron from bisglycinate and trisglycinate is regulated normally by iron status.