Unravelling breast milk composition: the diversity and function of human milk oligosaccharides (HMOs)

Breast milk is a hugely complex substance that contains thousands of molecules, interacting with each other in a unique way. Human milk oligosaccharides are one of its components next to lactose, lipids, bacteria and their metabolites. New research published in Nutrients reveals galactosyllactoses, one kind of HMOs, are present in breast milk at different stages of breastfeeding.

Breastfeeding is good for both baby and mother. It supports optimal growth and development of the baby and has positive health benefits for mom too. Breast milk provides a baby with a complex and diverse matrix of nutritional and bioactive compounds and is tailored to the nutritional needs of the baby. Research has shown its composition varies throughout breastfeeding stages. It can even change over the course of one feeding, adapted to a baby’s health and development status.

Human milk oligosaccharides are the third largest component of breast milk solids after lactose and lipids. Research has shown they have a prebiotic effect by stimulating growth and activity of beneficial gut bacteria, and;

  • Can have a direct effect on immune cells
  • Can block infections
  • Function as building blocks for a baby’s brain

There are more than 200 individual and unique HMOs in breast milk and new ones continue to be identified. The concentration of oligosaccharides in breast milk varies within and among women and is influenced by various factors, including the stage of breastfeeding, the mom’s diet, body mass index, ethnicity, socioeconomic status and genetic predisposition. Research in the field has focused on 20 of these HMOs, mostly the most abundant ones.

Recently galactosyllactoses (GLs), a group of small oligosaccharides was identified. Although GLs appear in low concentrations they are found to contribute to modulation of immune cells in a baby’s gut. The PreventCD study is one of the biggest studies so far as part of which the presence and relative levels of HMOs in a large number of breast milk samples (N=715) were analyzed during the first 4 months after birth.

"This study is unique in analyzing the most abundant and important HMOS, including the limitedly studied galactosyllactoses, in a large number of breast milk samples of women from across Europe. The study adds to our understanding of the complex composition of breast milk and the factors influencing its composition and how it impacts a baby’s growth and development."

Lead investigator Dr Simone van Eussen, Danone Nutricia Research

The results reinforce that HMO-levels in breast milk are highly variable. The total amount of HMOs decreased to less than half during the first 4 months after birth and there are clear differences in HMO presence and levels between women. The analyses have further shown that 3’-GL and 6’-GL, two specific types of galactosyllactoses, shown to support in the maturation of the immune system, are present in more than 75% of the breast milk samples that were studied. Similar to other important HMOs, like 2’-FL, the galactosyllactoses were present in higher or lower concentrations depending on mom’s genetics. Contrary to the overall trend of decreasing levels of HMOs over the course of breastfeeding stages the levels of of galactoyllactoses are relatively stable over the course of breastfeeding stages.

Breast milk is the best possible nutrition for all infants. It provides the optimal nutritional balance for each individual infant, being specifically adapted and uniquely formulated to fully support their growth and development needs. We support World Health Organization’s recommendation of exclusive breastfeeding for the first six months, with continued breastfeeding along with appropriate complementary foods for two years and beyond.

Are you a healthcare professional or (carer of) a diagnosed patient?

The product information for this area of specialization is intended for healthcare professionals or (carers of) diagnosed patients only, as these products are for use under healthcare professional supervision.

Please click ‘Yes’ if you are a healthcare professional or (carer of) a diagnosed patient, or ‘No’ to be taken to a full list of our products.

The information on this page is intended for healthcare professionals only.

If you aren't a healthcare professional, you can visit the page with general information, by clicking 'I'm not a healthcare professional' below.