Iron Absorption from an Iron-Fortified Follow-Up Formula with and without the Addition of a Synbiotic or a Human-Identical Milk Oligosaccharide: A Randomized Crossover Stable Isotope Study in Young Thai Children

Background: Previous studies showed that pre-and probiotics may enhance iron absorption.Probiotics combined with prebiotics (synbiotics), including human-identical milk oligosaccharides (HiMOs), are commonly added to infant and follow-up formula (FUF).Whether these additions enhance iron absorption from iron-fortified commercial milk formula is uncertain.Objectives: We determined the effect of adding 1) a synbiotic [galacto-oligosaccharide [GOS] þ Limosilactobacillus reuteri (L.reuteri)] or 2) the HiMO 2 0 -fucosyllactose (2 0 FL) to iron-fortified FUF on iron absorption in young Thai children.Methods: In a randomized, controlled, single-blinded (participants) crossover study, 82 Thai children aged 8-14 mo were enrolled to consume single servings (235 mL) of FUF with isotopically labeled ferrous sulfate (2.2 mg iron) with 1) the synbiotic (400 mg/100 mL GOS and L. reuteri DSM 17938), 2) the HiMO 2 0 FL (100 mg/100 mL), and 3) without synbiotic and 2 0 FL (control) in random order and a 3d washout period between administrations.Fractional iron absorption [FIA (%)] was assessed by measuring erythrocyte incorporation of isotopic labels 14 d (n ¼ 26) and 28 d (n ¼ 76) after consumption of the last test FUF.Results: Median (IQR) FIA from iron-fortified FUF with the synbiotic [8.2 (5.2, 12.9)%] and with 2 0 FL [8.4 (5.5, 14.1)%] did not differ from the control FUF [8.1 (4.8,14.7)%](synbiotic compared with control, P ¼ 0.24; 2 0 FL compared with control, P ¼ 0.95).FIA from all FUF did not differ when measured after 14 and 28 d of erythrocyte incorporation (Time, P ¼ 0.368; FUF, P ¼ 0.435; Time  FUF, P ¼ 0.937).Fecal pH and hemoglobin were negatively associated with FIA.Conclusions: In young Thai children, the addition of a synbiotic (GOS þ L. reuteri) or 2 0 FL to iron-fortified FUF did not impact FIA from a single serving.The study was registered at clinicaltrials.govas NCT04774016.