Iron Bioavailability from Ferric Pyrophosphate in Extruded Rice Cofortified with Zinc Sulfate Is Greater than When Cofortified with Zinc Oxide in a Human Stable Isotope Study.
Background:Extruded rice grains are often cofortified with iron and zinc. However, it is uncertain if the addition of zinc to iron-fortified rice affects iron absorption and whether this is zinc-compound specific.Objective:We investigated whether zinc, added as zinc oxide (ZnO) or zinc sulfate (ZnSO4), affects human iron absorption from extruded rice fortified with ferric pyrophosphate (FePP).Methods:In 19 iron-depleted Swiss women (plasma ferritin ≤16.5 μ/L) aged between 20 and 39 y with a normal body mass index (in kg/m2; 18.7-24.8), we compared iron absorption from 4 meals containing fortified extruded rice with 4 mg Fe and 3 mg Zn. Three of the meals contained extruded rice labeled with FePP (57FePP):1) 1 meal without added zinc (57FePP-Zn),2) 1 cofortified with ZnO (57FePP+ZnO), and3) 1 cofortified with ZnSO4(57FePP+ZnSO4). The fourth meal contained extruded rice without iron or zinc, extrinsically labeled with ferrous sulfate (58FeSO4) added as a solution after cooking. All 4 meals contained citric acid. Iron bioavailability was measured by isotopic iron ratios in red blood cells. We also measured relative in vitro iron solubility from57FePP-Zn,57FePP+ZnO, and57FePP+ZnSO4expressed as a fraction of FeSO4solubility.Results:Geometric mean fractional iron absorption (95% CI) from57FePP+ZnSO4was 4.5% (3.4%, 5.8%) and differed from57FePP+ZnO (2.7%; 1.8%, 4.1%) (P< 0.03); both did not differ from57FePP-Zn: 4.0% (2.8%, 5.6%). Relative iron bioavailabilities compared with58FeSO4were 62%, 57%, and 38% from57FePP+ZnSO4,57FePP-Zn, and57FePP+ZnO, respectively. In vitro solubility from57FePP+ZnSO4differed from that of57FePP-Zn (14.3%;P< 0.02) but not from that of57FePP+ZnO (10.2% compared with 13.1%;P= 0.08).Conclusions:In iron-depleted women, iron absorption from FePP-fortified extruded rice cofortified with ZnSO4was 1.6-fold (95% CI: 1.4-, 1.9-fold) that of rice cofortified with ZnO. These findings suggest that ZnSO4may be the preferable zinc cofortificant for optimal iron bioavailability of iron-fortified extruded rice. This trial was registered at clinicaltrials.gov as NCT02255942.
Laboratory for Human Nutrition, Institute of Food, Nutrition and Health, Swiss Federal Institute of Technology Zürich, Zurich, Switzerland; laura.hackl@hest.ethz.ch diego.moretti@hest.ethz.ch.
Laura
0000-0002-2645-1200
L
Hackl
Laboratory for Human Nutrition, Institute of Food, Nutrition and Health, Swiss Federal Institute of Technology Zürich, Zurich, Switzerland.
Michael B
MB
Zimmermann
Laboratory for Human Nutrition, Institute of Food, Nutrition and Health, Swiss Federal Institute of Technology Zürich, Zurich, Switzerland.
Christophe
0000-0001-6675-3708
C
Zeder
PATH, Seattle, WA; and.
Megan
0000-0003-0260-9445
M
Parker
Abbott Laboratories, Columbus, OH.
Paul W
0000-0001-8630-2736
PW
Johns
Laboratory for Human Nutrition, Institute of Food, Nutrition and Health, Swiss Federal Institute of Technology Zürich, Zurich, Switzerland.
Richard F
0000-0001-9328-7300
RF
Hurrell
Laboratory for Human Nutrition, Institute of Food, Nutrition and Health, Swiss Federal Institute of Technology Zürich, Zurich, Switzerland; laura.hackl@hest.ethz.ch diego.moretti@hest.ethz.ch.
Diego
0000-0002-7366-2182
D
Moretti
D000328:Adult; D001682:Biological Availability; D011756:Diphosphates / Q000737:chemistry / Q000378:metabolism*; D005260:Female; D005511:Food Handling; D005527:Food, Fortified; D006801:Humans; D007501:Iron / Q000737:chemistry / Q000378:metabolism / Q000493:pharmacokinetics*; D007503:Iron Isotopes / Q000493:pharmacokinetics; D012275:Oryza / Q000737:chemistry*; D055815:Young Adult; D015034:Zinc Oxide / Q000494:pharmacology*; D019287:Zinc Sulfate / Q000737:chemistry / Q000494:pharmacology*
D011756:Diphosphates; D007503:Iron Isotopes; D019287:Zinc Sulfate; D007501:Iron; C049051:ferric pyrophosphate; D015034:Zinc Oxide
fortification; human iron absorption; iron deficiency; rice; zinc-iron interaction