New Science studies show human milk is a regulated biological system, not just diet reflection

Human milk functions as a highly regulated biological system rather than a simple mirror of maternal diet, according to findings from two major international studies published Oct. 8 in Science. The research indicates that while certain components react to nutritional supplementation, others remain stable or serve as indicators of lactation biology and infant growth patterns.

The IMiC Consortium’s Global Scope

Conducted by the International Milk Composition (IMiC) Consortium, the work represents a global collaboration led by the University of Manitoba. The group involves more than 20 researchers from 13 organizations across six countries and four continents. Funded by the Gates Foundation, IMiC was established to analyze human milk as a complex biological entity instead of treating it merely as a collection of nutrients.

Dr. Meghan Azad, director of IMiC and a Canada Research Chair in early nutrition at the University of Manitoba, emphasized the dual nature of these findings. “Together, the studies show that human milk is neither completely fixed nor simply a reflection of maternal diet,” Azad said. She noted that some elements respond readily to interventions, while others are tightly regulated or reflect the biology of the lactating breast.

Analysis of Diverse Populations

Azad, also a professor of pediatrics and child health at the Max Rady College of Medicine and a research scientist with Children’s Hospital Research Institute of Manitoba, described this effort as one of the largest and most comprehensive attempts to study milk complexity across diverse populations. More than 1,000 mother and infant pairs participated, hailing from Canada, Burkina Faso, Tanzania and Pakistan.

The mothers contributed nearly 2,000 human milk samples. These specimens underwent analysis for more than 25,000 compounds, providing a detailed dataset on how milk composition varies across different geographic and demographic contexts.

Impact of Maternal Supplementation

The first study focused on how maternal nutritional supplements during lactation modify specific parts of breast milk. Results showed that components such as B vitamins, selenium and triglyceride profiles respond clearly to supplementation, whereas other elements do not change. This distinction highlights that milk is not simply a reflection of what a mother eats but a regulated system.

Dr. Trenton Dailey-Chwalibóg, lead author and senior research fellow at Ghent University’s Faculty of Bioscience Engineering, explained the implications. “At the same time, identifying which milk components are modifiable opens the door to designing maternal nutritional supplements more deliberately, with the goal of optimizing what is delivered to the infant through milk,” he said. Dailey-Chwalibóg also serves as principal investigator at Agence de Formation, de Recherche & d’Expertise en Santé pour l’Afrique (AFRICSanté) in Burkina Faso.

The data suggests that nutritional supplementation after birth may improve the micronutrient content of milk received by breastfed infants. This finding is particularly relevant in settings where maternal undernutrition is common.

Mammary Gland Function Insights

The second study discovered that milk offers clues about how the lactating breast functions and how this relates to infant growth. Researchers identified shared patterns in human milk linked to distinct aspects of mammary gland function, including milk synthesis and secretion, epithelial barrier and tissue remodeling, and immune and repair activity.

Dr. Liat Shenhav, study senior author and assistant professor at New York University’s Grossman School of Medicine, highlighted the diagnostic potential of these findings. “Human milk gives us a rare, non-invasive window into the biology of the lactating mammary gland,” Shenhav stated. “By looking at molecular patterns across diverse populations, we can begin to identify shared features of mammary function and understand how they relate to maternal metabolism and infant growth.”

The results demonstrate the value of examining milk within the context of mammary gland biology to better understand links between maternal metabolism and infant growth. These insights open new directions for understanding lactation biology and designing future interventions to support maternal nutrition, mammary function and infant growth.