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Changes in Iron Absorption After Roux-en-Y Gastric Bypass

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Iron deficiency is one of the most common deficiencies that may occur after Roux-en-Y gastric bypass (RYGB). Little is known about the optimal treatment of post-RYGB iron deficiency.


The aim of this study is to evaluate the changes in iron absorption characteristics after RYGB for two oral iron formulations, one presented in tablet form and one as in the form of a solution.


Iron absorption in 24 obese women was studied before and 1 month after RYGB. Twelve patients were tested with a single dose of 600 mg ferrous fumarate in tablet form (195 mg of elementary iron, group 1), and 12 patients received a single dose of 1390 mg ferrous gluconate as a solution (160 mg of elementary iron, group 2). Serum iron levels were measured before (T0) and every hour after ingestion of the supplement (T1–T9).


Before surgery, iron absorption was similar for the two supplements (P = 0.71). However, RYGB was associated with a decrease in fumarate iron absorption (P < 0.001) but did not affect gluconate iron absorption (P = 0.13). Postoperative absorption of fumarate iron was significantly lower than gluconate iron at T1 (P < 0.05), but the overall difference over 9 h did not reach statistical significance (P = 0.53).


RYGB adversely affects the absorption of ferrous fumarate tablets but not that of solubilized ferrous gluconate. A solubilized supplement is therefore preferred as the supplement of first choice after RYGB.

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We would like to thank Dr. L Roovers for her significant contribution to the statistical analyses.

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Correspondence to Wendy Schijns.

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The study was approved by the national ethics and was registered at as NCT02228902. All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.

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The authors declare that they have no conflict of interest.

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Informed consent was obtained from all individual participants included in the study.

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Schijns, W., Ligthart, M.A.P., Berends, F.J. et al. Changes in Iron Absorption After Roux-en-Y Gastric Bypass. OBES SURG 28, 1738–1744 (2018).

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