- The discovery of human milk oligosaccharides, which are carbs that nourish not the baby but friendly bacteria in the baby's gut
- Differences in milk consumed by male and female infants (I had never heard of this before!)
- New research on how breastmilk influences infant gene expression
I liked the way the author framed these discoveries at the end:
The diverse ingredients of an infant's first meal have an impact on its development, and no matter how much we tinker with the composition of formula milk it will always lack many of the trace constituents of human milk. As research identifies these substances, it increasingly seems they serve a role beyond direct nutritional benefit: that of communicating information to the infant about the environment and even the social structure around the mother...
It is easy to see breastmilk as "just food" and anything we use to replace it as just a different kind of food. I attended an excellent lecture a while back where the speaker spent 15-20 minutes discussing breastfeeding's immunological properties, effects on gene expression, effects on maternal health and child spacing, etc. and at the end said "Oh yeah - and it provides calories". When we think about it this way, breastmilk is not "just food" - it is a way of preparing and adapting the baby to its environment (and in the case of its effects on maternal hormones, health, and fertility, the biological changes of breastfeeding are adapting the mother to the baby).
I would take a little farther and say that when we think about the act of breastfeeding more broadly in a social context, we also communicate to babies (and children, and adults!) important things about their environment. This happens both on the individual level - the time a breastfeeding mother spends skin-to-skin, holding her baby, talking and interacting with her baby - as well as on a larger scale. When what society has deemed the "optimal" method of infant feeding is supposed to take place in a public restroom lest it offend, we communicate important things about the value of parenting and of young children. When mothers are extensively supported and nurtured in how they've chosen to feed their babies, we again communicate important things about how we value those mothers' mental and physical health. As breastmilk is not "just food", the act of breastfeeding is not just transferring food into a baby, but a way to see how we see mothers, mothering, and infant care.