The Totally Insane Way That Breast Milk Works

By Alissa Walker on at

I know breast milk is good and all, but when I became a mum I was kinda shocked at how often it was cited as a cure-all for anything that ailed my newborn. That’s not just because of the nutritional value. It turns out my baby’s immune system is communicating with mine THROUGH MY NIPPLES. And now that I know how it works, I kid you not when I say I am staring down at my boobs in wonderment.

Breast milk is hyped as some kind of wonder drug by doctors, mummyblogs, and real-life parents (including my own). Baby slices up her face with teensy Edward Scissorhands nails? Rub some breast milk on the cuts. Baby’s eyes crust over with a greenish glaze? Drop some breast milk under her eyelid. Acne? Wash her face with breast milk. Runny nose? Squirt some breast milk up one nostril. Coughing/chills/fever/headache? Breast milk, breast milk, breast milk. Breast milk!

All along I assumed breast milk was good for those things because of, like, nutrients and stuff. But then I started to hear even crazier shit, like how my milk has been slowly customizing itself to my baby’s needs over the months, recalibrating for her age and even the temperature outside (in hotter weather it hydrates your baby more effectively, for example). But I didn’t understand how any of this was possible until I read this story by Angela Garbes in The Stranger.

Grabs talks to Katie Hinde, an evolutionary biologist behind the blog Mammals Suck... Milk, who explains the incredible exchange of data that occurs between a boob and a baby:

According to Hinde, when a baby suckles at its mother’s breast, a vacuum is created. Within that vacuum, the infant’s saliva is sucked back into the mother’s nipple, where receptors in her mammary gland read its signals. This “baby spit backwash,” as she delightfully describes it, contains information about the baby’s immune status. Everything scientists know about physiology indicates that baby spit backwash is one of the ways that breast milk adjusts its immunological composition. If the mammary gland receptors detect the presence of pathogens, they compel the mother’s body to produce antibodies to fight it, and those antibodies travel through breast milk back into the baby’s body, where they target the infection.


As you might guess, for this and many other reasons, breast milk is of great interest to scientists in areas from microbiology to food chemistry. And researchers are only really beginning to understand how breast milk works. The entire story is a fascinating read that has got me thinking about my role as a new mom and I’m very glad that I finally understand the science behind how these two baby spit data collectors I carry around actually work. [The Stranger via Ann Friedman Weekly]

Photo by Zdenek Fiamoli