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Is extrinsic isotope labeling of plant foods reliable for studies of iron absorption?
Author(s) -
Jin Fuxia,
Rutzke Mike,
Welch Ross M.,
Glahn Raymond P.
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.6.a1115
Subject(s) - bioavailability , food science , chemistry , pellet , pinto bean , zoology , biology , botany , bioinformatics , phaseolus
The equilibration and uptake of extrinsic 58 Fe and intrinsic 56 Fe from a series of samples [i.e., control medium (Ctrl), FeCl 3 + ascorbic acid (Fe + AA), white great northern beans (both in pureed or non‐pureed meals) ± orange juice (OJ), and colored pinto beans (both in pureed or non‐pureed meals) ± OJ] wasdetermined using an in vitro digestion/Caco‐2 cell culture model. The ratio of 58 Fe /56 Fe in Caco‐2 cells, supernatants and pellets of the digest, was analyzed by ICP‐MS. The ratio of 58 Fe/ 56 Fe in Ctrl, Fe + AA and bean samples were ~0.003, 0.008 and 0.01, respectively. The 58 Fe/ 56 Fe ratios in the supernatant and pellet of pinto bean digest were ~0.005 and ~0.01, respectively. The decreased 58 Fe/ 56 Fe ratio in the supernatant of pinto bean digest was most likely the result of poor equilibration between extrinsic and intrinsic Fe resulting in 58 Fe being disproportionately retained in the insoluble Fe pools in the pellet. The Caco‐2 cells exhibited a 58 Fe/ 56 Fe ratio of ~0.005 after treatment with the pinto bean sample digests. In sample digests of great northern beans, the 58 Fe/ 56 Fe ratio of ~0.01 was found in both supernatant and pellet. However, the ratio of 58 Fe/ 56 Fe in the Caco‐2 cells was ~0.01 and ~0.005 after treatments by pureed and non‐pureed great northern bean samples, respectively. Possibly, this was caused by either a poor equilibration of 58 Fe and 56 Fe between bioavailable and non‐bioavailable Fe pools inside the non‐pureed bean sample digest, or by a preferential uptake of one isotope over another in some food matrices. This possibility was supported by the finding that the 58 Fe/ 56 Fe ratio in Caco‐2 cells was higher in cells receiving Ctrl but lower in cells treated with Fe + AA.