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ORIGINAL RESEARCH article

Front. Nutr.
Sec. Nutrition and Metabolism
Volume 11 - 2024 | doi: 10.3389/fnut.2024.1507156
This article is part of the Research Topic Human Milk, Nutrition and Infant Development, Volume II View all articles

Acute effect of aerobic exercise on human milk insulin concentrations: A randomised cross-over-study

Provisionally accepted
Rebecca Lyng Holm Rebecca Lyng Holm 1Mads Holmen Mads Holmen 1Md Abu Jafar Sujan Md Abu Jafar Sujan 1,2Guro Fanneløb Giskeødegård Guro Fanneløb Giskeødegård 3Trine Moholdt Trine Moholdt 2,4*
  • 1 Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway
  • 2 Department of Obstetrics and Gynaecology, St Olav's University Hospital, Trondheim, Sør-Trøndelag, Norway
  • 3 Department of Public Health and Nursing, Norwegian University of Science and Technology, Trondheim, Norway
  • 4 Faculty of Medicine, Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway

The final, formatted version of the article will be published soon.

    Insulin is present in human milk and its concentration correlates with maternal circulating levels. Studies on the association between human milk insulin concentrations and infant weight or growth show conflicting results, but some indicate that higher insulin concentrations in the milk can promote infant weight gain. Circulating levels of insulin decrease acutely after exercise, but no prior study has investigated the acute effect of exercise on human milk insulin concentrations. Our aim was to determine the acute effects of two endurance exercise protocols on human milk insulin concentration in exclusively breastfeeding individuals.In a randomised cross-over trial, 20 exclusively breastfeeding participants who were 6-12 weeks postpartum completed three conditions on separate days: 1) Moderate-intensity continuous training (MICT), 2) High-intensity interval training (HIIT), and 3) No activity (REST). Milk was collected before exercise/rest (at 07:00 h), immediately after exercise/rest (11:00 h), 1 h after exercise/rest (12:00 h), and 4 h after exercise/rest (15:00 h). We determined insulin concentrations in the milk using enzyme-linked immunosorbent assay and compared insulin concentrations after MICT and HIIT with REST using a linear mixed model with time-points and the interaction between time and condition as fixed factors.We detected insulin in all 240 samples, with an average concentration of 12.3 (SD 8.8) μIU/mL (range 3.2 -57.2 μIU/mL). There was no statistically significant effect of exercise on insulin concentration, but a tendency of reduced concentrations 4 h after HIIT (p = .093). There was an overall effect of time at 11:00 h and 15:00 h. In the fasted sample obtained at 07:00 h, the concentration was 9.9 (SD 7.2) μIU/mL, whereas the concentration was 12.7 (SD 9.0) μIU/mL at 11:00 h (p = .009), and 15.0 (SD 11.7) μIU/mL at 15:00 h (p < .001).One session of aerobic exercise, either at moderate-or high intensity, had no statistically significant effect on human milk insulin concentration. Future research should determine the effect of regular exercise on insulin in human milk and potential impact for infant health outcomes. Registration number in ClinicalTrials.gov: NCT05042414

    Keywords: Obesity, Lactation, Metabolism, High-intensity interval training, Infant, nutrition, Running

    Received: 07 Oct 2024; Accepted: 30 Dec 2024.

    Copyright: © 2024 Holm, Holmen, Sujan, Giskeødegård and Moholdt. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

    * Correspondence: Trine Moholdt, Faculty of Medicine, Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, 7022, Norway

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