Kinetics of Iron Absorption From Ferrous Fumarate With Galacto-oligosaccharides Measured by Stable-isotope Appearance Curves in Iron Depleted Women in Switzerland

Abstract Objectives Prebiotic galacto-oligosaccharides (GOS) have shown promising results in enhancing the absorption of oral supplemental iron in form of ferrous fumarate (FeFum) in iron depleted adults. The mechanism behind this effect is unknown. We aimed to assess the absorption profile of FeFum given with and without GOS using stable isotope appearance curves (SIACs). Methods We conducted a controlled, single-center, prospective cross-over trial in iron depleted women between Sept and Nov 2019 at the Laboratory of Human Nutrition, ETH Zurich, Switzerland. All women (n = 11; median SF = 15.2 µg/L) received two supplemental iron doses of 14 mg in form of FeFum containing 6 mg of isotopic tracers (57Fe or 58Fe). The supplemental iron doses were administered in random order on d 1 and 15 after an overnight fast. The supplement combinations were: 1) 57FeFum + 300 ml water; and 2) 58FeFum + 15 g GOS + 300 ml water. Eleven blood samples were collected up to 24 h after administration of the iron supplements to determine serum iron appearance. Fractional iron absorption (FIA) of the isotopic tracers was calculated in whole blood collected 14 days after administration of each of the supplemental iron doses on the basis of the shift in iron isotope ratios according to the principle of isotope dilution. Results There was a trend towards increased FIA and total absolute AUC of the SIAC from FeFum given with 15 g GOS compared to without (P = 0.064; P = 0.080 respectively). Estimated timepoints of the peak serum isotope concentration were not different (P = 0.096). Relative SF and relative bioavailability correlated significantly (P = 0.037). In subjects with a lower SF the increase in bioavailability of iron when given with GOS was more pronounced compared to participants with higher SF. Conclusions Adding 15 g GOS to FeFum did not result in a different absorption profile compared to without GOS. The enhancing effect of GOS seems to depend on iron status, even though overall the improvement of iron absorption when given with 15 g GOS did not reach significance, probably due to the small sample size. Since women with a low iron status can benefit the most from an increase in iron bioavailability, the use of GOS for the improvement of iron bioavailability from FeFum in women with very low iron stores is promising. Funding Sources Innosuisse, Swiss Innovation Agency, in collaboration with Antistress AG - Burgerstein Vitamine.