Iron Absorption from Bouillon Fortified with Iron-Enriched Aspergillus oryzae Is Higher Than That Fortified with Ferric Pyrophosphate in Young Women

BACKGROUND: Bouillon cubes are a potential vehicle for iron fortification. They are currently fortified with ferric pyrophosphate (FePP), which is known to be poorly absorbed. The objective of this study was to assess the iron absorption of Aspergillus oryzae grown in FePP (ASP-p) and compare it with FePP and ferrous sulfate (FeSO(4))–fortified bouillon cubes. METHODS: In 2 single-blinded, crossover studies, healthy women with serum ferritin concentrations <40 μg/L were randomly assigned to consume a rice-vegetable meal with iron-fortified chicken bouillon. Subjects in study I (n = 17, 18–26 y) consumed iron from both iron sources as (57)FePP and (58)ASP-p (intrinsically labeled with (58)FePP) with a meal containing 4.2 mg of total iron provided for 3 d. Study II (n = 18, 18–29 y) was similar except that subjects consumed (57)FeSO(4) and (58)ASP-p. Whole-blood stable isotope enrichment after 14 d was used to measure fractional iron absorption. Hemoglobin, hematocrit, serum ferritin, hepcidin, and serum C-reactive protein were analyzed at baseline and at 14 d. A t test was used to compare the mean differences in fractional absorptions within each study and baseline characteristics between studies. RESULTS: Geometric mean (95% CI) fractional iron absorption of FePP [0.94% (0.63%, 1.40%)] was lower than ASP-p [2.20% (1.47%, 3.30%)] (P < 0.0001) in study I. In study II, ASP-p fractional absorption [2.98% (2.03%, 4.38%)] was lower than that of FeSO(4) [9.88% (6.70%, 14.59%)] (P < 0.0001). Both ferritin (r = −0.41, P = 0.014) and hepcidin (r = −0.42, P = 0.01) concentrations were inversely correlated with ASP-p iron absorption. Fractional absorption of ASP-p was also positively correlated with FePP (r = 0.92, P < 0.0001) and FeSO(4) (r = 0.52, P < 0.02) absorption. CONCLUSIONS: ASP-p–fortified bouillon provided 2.3-fold higher absorbable iron than the currently used FePP. Bouillon fortified with ASP-p may contribute sufficient bioavailable iron to meet the daily iron requirements in young women only if consumed with other iron-fortified staple foods. This trial was registered at clinicaltrials.gov as NCT03586245.