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Macronutrient Content in Human Milk Is Not Affected by Infant’s Sex †

Department of Clinical Research, Faculty of Health Science, University of Southern Denmark, 5000 Odense, Denmark
Hans Christian Andersen Children’s Hospital, Odense University Hospital, 5000 Odense, Denmark
Department of Anesthesiology, Odense University Hospital, 5000 Odense, Denmark
Research Unit OPEN, Department of Clinical Research, University of Southern Denmark, 5000 Odense, Denmark
Department of Nutrition, Exercise and Sports, University of Copenhagen, 1958 Frederiksberg, Denmark
Author to whom correspondence should be addressed.
Presented at the Australian Breastfeeding + Lactation Research and Science Translation Conference (ABREAST Conference 2023), Perth, Australia, 10 November 2023.
Proceedings 2023, 93(1), 18;
Published: 27 December 2023


Human milk contains macronutrients possibly affecting infant and early childhood growth. Most studies suggest a sex-specific difference in macronutrient levels in favor of males, with a higher energy content from fat, lactose, and protein. Further, macronutrient levels may differ according to mixed or exclusive breastfeeding; however, the literature is inconsistent. Our aim was to investigate sex-specific differences in macronutrient content in exclusively breastfed infants in a Danish child cohort, and whether macronutrient levels differed between exclusive or mixed (breast and formula) breastfeeding. Participants were part of the prospective birth cohort Odense Child Cohort. Baseline characteristics were obtained from medical records. Weekly SMS questions were sent to the mothers until the cessation of breastfeeding, asking whether they were breastfeeding and/or formula feeding. Mothers delivered a milk sample at the planned 3–4-month examination of the infant. Macronutrient analyses were performed on 182 samples using mid-infrared transmission spectroscopy (Miris Human milk Analyzer). We included 150 mother–infant dyads with both macronutrient analysis, and SMS data on breastfeeding. Baseline characteristics did not differ according to sex. The median interquartile range (IQR) infant age at the time of sampling was 4.1 (3.7–4.5) months. A total of 39 males and 38 females were exclusively breastfed at the time of milk sampling, while 36 males and 37 females were mixed-fed. We found no significant sex-specific differences in macronutrients among exclusively breastfed infants. The median (IQR) levels for males and females, respectively, were; protein, 0.85 g/100 mL (0.77, 0.90), and 0.82 g/100 mL (0.80, 0.90), p = 0.91; lactose, 7.83 g/100 mL (7.70, 7.95), and 7.73 g/100 mL (7.53, 7.90), p = 0.17; fat, 3.23 g/100 mL (2.07, 4.37), and 3.07 g/100 mL (2.10, 3.60), p = 0.34; energy, 65.5 kcal/100 mL (54.17, 77.00), and 63 kcal/100 mL (56.00, 69.33), p = 0.13. Further, we found no significant differences in macronutrient content in human milk samples from exclusively versus mixed-feeding mothers either prior and after adjusting for confounders, p > 0.36. This study does not confirm the previous findings of sex-specific differences in macronutrients in human milk. It is still unknown if sex-specific formula products tailored to meet possible sex-specific requirements can optimize child growth. Further research on this topic is needed.

Author Contributions

Conceptualization, K.D.H., S.B., and G.Z.; methodology, K.D.H., S.B., S.M., and G.Z.; Formal analysis, K.D.H.; investigation K.D.H.; resources, K.D.H.; data curation, K.D.H., S.B., and S.M.; writing—original draft preparation, K.D.H.; writing—review and editing, K.D.H., S.B., S.M, K.F.M., S.H., and G.Z.; supervision, G.Z.; project administration, K.D.H.; funding acquisition, K.D.H. All authors have read and agreed to the published version of the manuscript.


This research was partially funded by the Region of Southern Denmark, the Faculty Scholarship from the University of Southern Denmark, and Arla Foods Ingredients.

Institutional Review Board Statement

The study was approved by The Regional Scientific Ethical Committee for Southern Denmark (project number S-20090130, sub-protocols 12 and 18) and The Danish Data Protection Agency (case number 12/26892). The study complied with the Declaration of Helsinki.

Informed Consent Statement

Informed consent was obtained from all subjects involved in the study.

Data Availability Statement

The data presented in this study are available on request from the corresponding author.


Thanks to all participating children and their families, as well as the employees at the Odense Child Cohort. Special thanks to scientific laboratory technician Mette Vogn Hviid for helping with the collection and processing of the milk samples.

Conflicts of Interest

K.D.H. has received funding from Arla Foods Ingredients and has received speaker fees from Nestlé Nutrition Institute. G.Z. has received speaker fees from Nestlé Nutrition Institute and Mead Johnson Nutrition Institute. S.B. was employed by Arla Foods Ingredients from February 2016 to January 2019 and has received speaker fees from Ordesa Group and Semper. K.F.M. has received research grants from the US Dairy Export Council and the Danish Dairy Research Foundation and has undertaken research in collaboration with Nutriset. S.H. has received unrestricted grants from Thermo-Fisher and Takeda and has been on an advisory board for Glaxo-Smith-Kline. The funders had no role in 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.
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MDPI and ACS Style

Honoré, K.D.; Bruun, S.; Möller, S.; Michaelsen, K.F.; Husby, S.; Zachariassen, G. Macronutrient Content in Human Milk Is Not Affected by Infant’s Sex. Proceedings 2023, 93, 18.

AMA Style

Honoré KD, Bruun S, Möller S, Michaelsen KF, Husby S, Zachariassen G. Macronutrient Content in Human Milk Is Not Affected by Infant’s Sex. Proceedings. 2023; 93(1):18.

Chicago/Turabian Style

Honoré, Karina D., Signe Bruun, Sören Möller, Kim F. Michaelsen, Steffen Husby, and Gitte Zachariassen. 2023. "Macronutrient Content in Human Milk Is Not Affected by Infant’s Sex" Proceedings 93, no. 1: 18.

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