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ORIGINAL RESEARCH article

Front. Nutr.

Sec. Nutritional Immunology

Volume 12 - 2025 | doi: 10.3389/fnut.2025.1618784

This article is part of the Research TopicHuman Milk, Nutrition and Infant Development, Volume IIView all 13 articles

Day/Night Fluctuations of Breast Milk Bioactive Factors and Microbiome

Provisionally accepted
Melissa  Ann WoortmanMelissa Ann Woortman1Haipeng  SunHaipeng Sun1Jincheng  WangJincheng Wang1Filipa  Godoy-VitorinoFilipa Godoy-Vitorino2Angeliz  J Rivera MeléndezAngeliz J Rivera Meléndez2Maribel  Campos RiveraMaribel Campos Rivera2Edna  E Aquino PiñeroEdna E Aquino Piñero2Krystin  EngelhardtKrystin Engelhardt1Lawrence  C KleinmanLawrence C Kleinman1Maria Gloria  Dominguez-BelloMaria Gloria Dominguez-Bello1*
  • 1Rutgers University, New Brunswick, United States
  • 2University of Puerto Rico, San Juan, Puerto Rico

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

Human breast milk is a sophisticated and complex biological fluid that provides crucial nutritional, immunological, and microbial benefits to infants. Hormones exhibit circadian variations in maternal serum, and understanding these fluctuations in breast milk is crucial for assessing infant maturation. This is particularly relevant when expressed breast milk is fed at a different time from when it was originally produced. This study examined 24-hour variations in breast milk composition by analyzing samples from 38 lactating mothers at four distinct times of the day. Levels of cortisol, melatonin, immunoglobulin A (IgA), lactoferrin, and oxytocin were quantified using ELISA, and microbiome composition was assessed through 16S rRNA sequencing. The results revealed significant 24-hour fluctuations in melatonin and cortisol concentrations, whereas lactoferrin and IgA levels only varied when separating by infant age, maternal BMI, or infant sex. Breast milk microbial composition shifted, with a nocturnal increase in skin-associated bacteria and a diurnal increase in environmental bacteria depending on maternal BMI and infant age. Additionally, milk microbiota alpha diversity increased due to age, but not consistently over all the time points. These results underscore the physiological relevance of maintaining the natural temporal dynamics of breast milk, which may be disrupted when expressed breast milk is fed asynchronously from its time of expression.To investigate the changes in breast milk throughout the day and night, samples were collected from three separate studies from two sites with similar protocols. The Rutgers Breast Milk Study (Rutgers Deleted: In

Keywords: Breast milk1, circadian2, milk microbiome3, hormones4, immune proteins5 Font: Not Italic, Font color: Blue Font: Not Italic, Font color: Blue

Received: 26 Apr 2025; Accepted: 28 Jul 2025.

Copyright: © 2025 Woortman, Sun, Wang, Godoy-Vitorino, Rivera Meléndez, Campos Rivera, Aquino Piñero, Engelhardt, Kleinman and Dominguez-Bello. 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: Maria Gloria Dominguez-Bello, Rutgers University, New Brunswick, United States

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