Associations of known and newly identified human milk oligosaccharides with infections in early childhood: The Ulm SPATZ Health Study

Linda P. Siziba^1*Zhuoxin Peng¹Marko Mank²Bernd Stahl^2,3John Gonsalves²Deborah Wernecke^4,5Dietrich Rothenbacher^4,5Jon Genuneit^4,6

• ¹Pediatric Epidemiology, Department of Paediatrics, Medical Faculty, Universitat Leipzig, Leipzig, Germany
• ²Danone Research & Innovation, Utrecht, Netherlands
• ³Department of Chemical Biology & Drug Discovery, Faculty of Science, Utrecht Institute for Pharmaceutical Sciences, Utrecht University,, Utrecht, Netherlands
• ⁴Universitat Ulm Institut fur Epidemiologie und Medizinische Biometrie, Ulm, Germany
• ⁵German Center for Child and Adolescent Health (DZKJ), partner site, Ulm, Germany
• ⁶Universitat Leipzig, Leipzig, Germany

Introduction: Human milk oligosaccharides (HMOs) are bioactive components of breast milk that play a key role in shaping infant immune development and susceptibility to infections. This study investigated associations between 71 known and novel HMOs measured at 6 weeks and 6 months postpartum with infant infections during the first two years of life. Methods: 73 HMOs were analysed in human milk sampled at 6 weeks (n = 144) and 6 months (n = 133) using LC-ESI-IM-qTOF-MS. Infections in infants were assessed using physician-reported questionnaires at 1 and 2 years. Modified Poisson regression was used to assess associations, adjusted for relevant covariates and corrected for multiple testing (FDR < 0.010). Results: Higher levels of Fucosyl(1-3)-iso-lacto-N-octaose, lacto-N-tetraose (LNT), and Sialyllacto-N-tetraose b (LSTb) at 6 weeks were associated with higher likelihood of lower respiratory tract infection (LRTI) at one year of age. In contrast, elevated Difucosyldisialyllacto-N-hexaose-X2 and Difucosyl-lacto-N-hexaose II in non-secretor milk were linked to reduced likelihood of otitis media (OM) cumulatively in the two-year period. Higher levels of LNT2 and LSTa in secretor milk at 6 months were associated with a higher likelihood of LRTI in the first and cumulatively up to the second year of life, respectively. This is a provisional file, not the final typeset article Conclusion: These findings suggest that specific HMOs may influence early-life infection susceptibility. However, the associations likely reflect a complex, dynamic balance in human milk composition, potentially driven by early microbial exposures or maternal responses. Further research is needed to clarify whether HMOs directly modulate susceptibility to infection or act through broader immunological pathways.