Abstract
The daily variation in human milk (HM) hormones and macronutrients is not well characterised and sample protocols are highly variable between studies. Method: During a 24 h period, the mothers (n = 10) hand-expressed small milk samples, immediately before and after each breastfeeding or expression from each breast. Test-weighing was used to determine the volume of HM consumed in each feed. Concentrations of leptin, adiponectin, insulin, fat, and glucose were measured by variable biochemical assays. A linear mixed model was fitted to eleven outcomes of leptin, adiponectin, insulin, fat, glucose (dose and concentration for each), and feed volume. The explanatory variables considered were a circadian cycle (cosine and sine terms), and for dose and concentration outcomes, an indicator variable for pre- or post-feed. The random effect was a circadian cycle (cosine and sine terms) for each mother. Results: The average infant intake of HM was 1060 mL/day (8 to 20 feeds/day). Pre- and post-feed differences were found in the concentrations of leptin, adiponectin, insulin, and fat (p < 0.05). Significant circadian variation across the 24 h period was found in adiponectin concentration, insulin (both concentration and dose), fat dose, glucose (both concentration and dose), and milk volume. Conclusion: These results highlight the importance of establishing standardised and rigorous sampling protocols considering all levels of variations (within-feed or circadian) to provide a better determination of the impact of these components on infant health and development.
Keywords:
human milk; lactation; breastfeeding; hormones; adipokine; macronutrient; circadian rhythm; variation Author Contributions
Conceptualization, M.A.S., D.T.G. and C.T.L.; data curation and writing—original draft, M.A.S. and C.T.L.; writing—review and editing D.T.G., C.T.L. and M.E.W.; visualization, A.R.; supervision, C.T.L., D.T.G. and M.E.W. All authors have read and agreed to the published version of the manuscript.
Funding
This work was supported by Jazan University, Saudi Arabia and Medela AG, Switzerland. M.A.S receives a postgraduate scholarship from Jazan University (Saudi Arabia). D.T.G. and C.T.L. receive salaries from an unrestricted research grant paid by Medela AG (Switzerland) and administered by The University of Western Australia.
Institutional Review Board Statement
This study was approved by The University of Western Australia’s Human Research Ethics Committee (RA/4/1/4492).
Informed Consent Statement
Informed consent was obtained from all participants involved in the study.
Data Availability Statement
Data sharing not applicable.
Conflicts of Interest
D.T.G. declares participation in the Scientific Advisory Board of Medela AG. M.A.S. received a postgraduate scholarship from Jazan University. D.T.G. and C.T.L. receive salary from an unrestricted research grant paid by Medela AG and administered by The University of Western Australia. The funding bodies had no input into the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content. |
© 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).