Humans may have the most complex breast milk of all mammals. Milk from a human mother contains more than 200 different sugar molecules, way above the average 30-50 found in, for example, mouse or cow milk. The role of each of these sugars and why their composition changes during breastfeeding is still a scientific puzzle, but it’s likely connected to the infant immune system and developing gut microbiome. A Review of what’s known and the different jobs of human breast milk appears in Trends in Biochemical Sciences.
Breast milk is often an infant’s first meal, but many of the sugar molecules in the milk are not meant to feed the baby. Infants are born sterile of any bacteria in their guts, but within a few days they have millions, and after a week there are billions. The sugars that come from mother’s milk are usually the first compounds that these bacteria have to chew on, a free lunch that is intended to culture specific bacterial species.
This image represents how breast milk provides more than just nutrients and vitamins to the suckling baby. Recent research demonstrated the functional complexity of breast milk components, including immunoglobulins, cytokines, antimicrobial proteins, hormones, and oligosaccharides. All of these molecules act in concert to fortify immunity, shape the gut microbiota, stimulate body growth, and even regulate birth spacing in mothers
Image Credit: Thierry Hennet