Unaltered 3'-sialyllactose and 6'-sialyllactose concentrations in human milk immediately after endurance exercise: a randomized crossover trial

Maëliss Cynthia Chloé Lemoine¹Leesa Klau²Mads Holmen¹Emily Rose Ashby^1,3Finn Lillelund Aachmann²Trygve Andreassen^1,4Guro Fanneløb Giskeødegård⁵Trine Moholdt^1,6*

• ¹Norges teknisk-naturvitenskapelige universitet Institutt for sirkulasjon og bildediagnostikk, Trondheim, Norway
• ²Norges teknisk-naturvitenskapelige universitet Institutt for bioteknologi og matvitenskap, Trondheim, Norway
• ³Department of Gynecology and Obstetrics, St. Olav's Hospital, Trondheim, Norway
• ⁴Central Staff, St. Olavs Hospital HF, Trondheim, Norway
• ⁵Norges teknisk-naturvitenskapelige universitet Institutt for samfunnsmedisin og sykepleie, Trondheim, Norway
• ⁶Department of Endocrinology, Clinic of Medicine, St. Olavs Hospital, Trondheim, Norway

Introduction: Human milk contains over 200 different types of human milk oligosaccharides (HMOs) with concentrations varying based on genetics, lifestyle, and time postpartum. Prior research indicates that exercise training during pregnancy leads to increased human milk concentration of the HMO 3'-sialyllactose (3'SL), potentially improving the offspring's metabolic development. The acute effect of postpartum exercise on HMOs concentrations in human milk is unknown. We aimed to evaluate the acute effect of moderate-and high-intensity endurance exercise on two selected sialylated HMOs in human milk. Methods: Twenty exclusively breastfeeding mothers to 6-12-weeks-old term infants were included in this randomized crossover trial. They completed three conditions in random order: no exercise (REST), moderate-intensity continuous training (MICT), and high-intensity interval training (HIIT). We collected human milk at 07:00 h, 11:00 h (immediately after rest/exercise), 12:00 h (1 h after rest/exercise) and 15:00 h (4 hrs after rest/exercise). Skimmed milk was analyzed by NMR spectroscopy to determine concentrations of 3'SL and 6'-sialyllactose (6'SL). We used a linear This is a provisional file, not the final typeset article mixed model to estimate the effect of exercise on the concentrations of the selected HMOs, compared with REST. Results: All participants completed the three conditions and were included in the analyses. Exercise had no statistically significant effect on 3'SL or 6'SL concentrations. The largest mean differences in 3'SL concentrations were observed immediately after rest/exercise: MICT yielded an increase of 10% (95% confidence interval (CI) -5% to 24%, p= .19) and HIIT of 4% (95% CI -10% to 19%, p= .55). Similarly, we observed the largest mean differences in 6'SL concentration immediately after MICT, with an increase of 5% (95% CI -6% to 15%, p= .40), whereas the greatest mean difference in 6'SL concentration was seen 1 h after HIIT (6%, 95% CI -5% to 16%, p= .31). No serious adverse events occurred. Conclusion: A single endurance exercise session had no statistically significant effect on 3'SL or 6'SL concentrations in human milk. Further research should determine the effect of regular exercise training on HMO concentrations. Registration number in ClinicalTrials.gov: NCT05042414.