The effects of 2'-fucosyllactose and lacto-N-neotetraose, galacto-oligosaccharides, and maternal human milk oligosaccharide profile on iron absorption in Kenyan infants

Background: Whether prebiotic human milk oligosaccharides (HMO), such as 2'-fucosyllactose (2'-FL) and lacto-N-neotetraose (LNnT), enhance iron absorption in infants is unknown. Moreover, whether maternal HMO profile affects absorption of iron fortificants or the effects of prebiotic galacto-oligosaccharides (GOS) and/or HMO on iron absorption is uncertain. Objectives: The aim of this study was to test whether consumption of 3.0 g GOS or HMO enhances iron absorption from iron-fortified maize porridge in partially breastfed Kenyan infants and whether maternal HMO profile modulates these effects. Methods: In a randomized, prospective crossover study, 55 infants (aged 8-12 mo) were fed test meals fortified with 1 of the following: 1) 5.0 mg iron as 54Fe-labeled ferrous fumarate (FeFum); 2) 5.0 mg iron as 58FeFum and 3.0 g GOS (FeFumthornGOS); and 3) 5.0 mg iron as (57)FeFum and 2.0 g 2'-FL and 1.0 g LNnT (FeFumthornHMO). Fractional iron absorption (FIA) was assessed by erythrocyte incorporation of iron isotopes. HMO profiles were determined by capillary gel electrophoresis with laser-induced florescence detection. Data were analyzed with mixed-effect models, and iron dialyzability was measured in vitro. Results: Of the 55 infants included, 49 were fed as instructed. FIA from the FeFumthornGOS group [median (IQR) 22.2% (16.5%-25.9%)] was higher than that from the FeFum group [12.5% (9.5%-20.9%)] (P = 0.005). FIA from the FeFumthornHMO group was 13.3% (7.1%-24.4%) and did not differ from the FeFum group (P = 0.923). Maternal HMO profile did not predict FIA or modulate the effects of GOS or HMO on FIA. Iron dialyzability ratios at pH 2 of FeFumthornGOS to FeFum and FeFumthornHMO to FeFum were 2.1 and 0.9 (P = 0.001 and P = 0.322), respectively. Conclusions: In Kenyan infants consuming FeFum-fortified maize porridge, co-provision of 3.0 g GOS increased FIA by 78%, whereas co-provision of 3.0 g HMO did not affect FIA. Variations in maternal HMO profile, including secretor and Lewis phenotype, did not predict FIA. These data argue against a physiologic role for 2'-FL and LNnT in facilitating iron absorption in infancy. The study was registered at clinicaltrials.gov as NCT04163406 (https://clinicaltrials.gov/ct2/show/NCT04163406).

Automated summary

This study aimed to test whether the intake of 3.0 g of galacto-oligosaccharides (GOS) or human milk oligosaccharides (HMO) enhances iron absorption from iron-fortified maize porridge in partially breastfed Kenyan infants, and whether the maternal HMO profile modulates these effects. The results showed that the intake of GOS increased iron absorption by 78%, while the intake of HMO did not affect iron absorption. Therefore, this study suggests that 2'-fucosyllactose (2'-FL) and lacto-N-neotetraose (LNnT) do not have a physiological role in facilitating iron absorption during infancy.