How Do Babies Get Milk Out of Breasts?

This article was originally posted on RealClearScience.

There’s a controversy surrounding breastfeeding. No, not the controversy about whether it’s appropriate for mothers to breastfeed in public, say, in front of a class of college students. Science can’t help with that one.

I’m talking about the other breastfeeding controversy: How do babies get milk out of those things, anyway? Apparently, the answer to that question has been the subject of a century-long debate. Who knew?!

Wait a minute, you must be thinking. Scientists are interested in breasts? Of course they are. In fact, they have even studied bouncing breasts. Don’t giggle. This is serious stuff.

You might think that the breastfeeding process is relatively straightforward: The baby latches on and sucks like a little Hoover vacuum cleaner. But, you would be wrong. The biomechanics of suckling are rather complicated. True, the baby does suck by lowering the atmospheric pressure in its oral cavity. However, it also “mouths” (i.e., squeezes the nipple and areola between its gums) and engages in “tongue peristalsis” (i.e., moving its tongue in a wavelike manner). See? Complicated. (If you are in need of a visual reminder of how suckling works, see this video clip of Jim Carrey from the movie Liar Liar.)

The scientific issue at the heart of this research, therefore, is, “Which of these suckling mechanisms is most responsible for extracting milk?” Finally, we may now have an answer to that question. Israeli and American scientists placed an imaging device under the chin of a breastfeeding mother and recorded ultrasound videos. And, thankfully, the prestigious journal PNAS found this research sufficiently compelling to publish in its gilded pages.

A screenshot from one of the videos is shown below.

They even went to the trouble of constructing a computer model.

After analyzing the videos and running simulations on their computer model, the scientists declared triumphantly: “We have resolved a century-long scientific controversy and demonstrated with a 3D biophysical model that infants suck breast milk by subatmospheric pressures and not by mouthing the nipple–areola complex to induce a peristaltic-like extraction mechanism.”

Translation: Babies suck.

Source: David Elad et al. “Biomechanics of milk extraction during breast-feeding.” PNAS. Published online before print: 24-March-2014. doi: 10.1073/pnas.1319798111