A friend and I were geeking out about breastfeeding today, and she said, "So what is the deal with foremilk and hindmilk?" She was referring to the thirst-quenching, lower-fat milk that babies get at the beginning of a feed and the satisfying, higher-fat milk that comes toward the end of a feed. These terms can be confusing, and some parents worry that their babies aren't getting enough hindmilk.
So do humans really make two types of milk? Are our breasts like those old-fashioned sinks that have separate faucets for hot and cold water? How much time does it take for a breast to "switch" from foremilk to hindmilk during a feeding?
The fact that we have two separate terms is at the root of the confusion around the fat content of human milk. Our milk always has fat in it, and as milk is removed, the level of fat gradually increases. There is no magical point during breastfeeding or expression when the foremilk shuts off and the hindmilk turns on. Several years ago, I came across a wonderful blog post that explains very well how this works, including a lineup of 12 vials of milk expressed over the course of a pumping session.
I couldn't pull up that blog post as I talked to my friend, who had just poured me a cup of tea. Looking at the tea, just beginning to steep, I saw an apt comparison. I told my friend that even freshly poured, the tea was starting to infuse into the hot water. The longer the tea bag stayed in the water, the stronger the infusion. This made sense to her, thinking of human milk as hot water and a tea bag as the fat. Spot of tea, anyone?