By Brian W. Donnelly, M.D., I.B.C.L.C.
“A pair of substantial mammary glands,” said Oliver Wendell Holmes the Elder in 1867, “has the advantage over the two hemispheres of the most learned professor’s brain in the art of compounding a nutritious fluid for infants.”
Is this an outdated idea?
Formula companies tell us that their product is as good as breast milk.
In fact, a few decades ago, their advertising told us it was even better than the real thing.
That claim was clever marketing, but proved to be unsustainable.
Researchers tell us that studying breast milk is interesting because it is a moving target, so to speak. For example, caloric content is usually higher at the end of a feeding compared to the beginning. According to Nicholas Day, author of the forthcoming book Baby Meets World, there is still a lot more to learn about breast milk:
When we come out of the womb, we make our way to the breast. We enter the world knowing we’re mammals, with milk on our minds.
But even as grown-ups, we have never known exactly what’s in that milk—or, as strange as it may sound, what the point of it is. For decades, milk was thought of strictly in terms of nutrients, which makes sense—milk is how a mother feeds her baby, after all. But providing nutrients turns out to be only part of what milk does. And it might not even be the most important part.
“Mother’s milk is food; mother’s milk is medicine; and mother’s milk is signal,” says Katie Hinde, an assistant professorof human evolutionary biology at Harvard. (She also writes the fascinating blog Mammals Suck, which I suspect is the only place on the Internet where you can fill out a Mammal Madness bracket.) “When people find out I study milk, they automatically think we already know about it, or it’s not important. And I’m like, ‘No, we don’t know about it, and it’s super important.’”
One of the intriguing findings is that the concentration of white blood cells that the mother delivers into the milk varies according to subtle distress signals that the infant sends to mom:
We think of milk as a static commodity, maybe because the milk we buy in the grocery store always looks the same. But scientists now believe that milk varies tremendously. It varies from mother to mother, and it varies within the milk of the same mother. That’s partly because the infants themselves can affect what’s in the milk. “Milk is this phenomenally difficult thing to study because mothers are not passive producers and babies are not passive consumers,” Hinde says. Instead, the composition of milk is a constant negotiation, subject to tiny variables.
For example, she notes, in humans skin-to-skin contact appears to trigger signals that are sent through the milk. “If the infant is showing signs of infection, somehow that’s being signaled back to the mother and she up-regulates the immune factors that are in her milk. Now is that her body’s responding to a need of the baby? Maybe. Is it that she also has a low-grade infection that she’s just not symptomatic for and so her body’s doing that? Maybe. Is it partially both? Maybe. We don’t know. It’s brand-new stuff.”
As Aretha Franklin told us, about 100 years after Mr. Holmes’ observation : “Ain’t nothing like the real thing, baby.”
**** Dr. Brian Donnelly is a pediatrician at Pediatric Alliance — North Hills Division. He is also a certified lactation consultant and is President of the Allegheny County Health Department Breastfeeding Coalition. ****
Read Nicholas Day’s interesting article at Slate.com here.