How does supply and demand work with breastfeeding?
Milk supply is primarily a process of supply and demand - meaning that the baby's "demand" is what determines the mother's milk supply. Here's how that works.
The process of your milk "coming in" in driven by hormones. During pregnancy, both prolactin and progesterone levels are high.
After the placenta is delivered, progesterone levels drop dramatically and your milk "comes in."
After your milk has "come in," the primary control mechanism for how much milk is produced is how much milk is removed.
This is controlled locally, in each breast.
As long as milk is being removed, your body may continue to produce milk.
Hormones, pregnancies, and other things can get in the way, but for some people lactating for an extended period of time (years) is possible.
This process doesn't always work perfectly, as anyone who has pumped around the clock to provide "demand" and hasn't seen a big change in milk production knows.
But it's important to keep in mind that when you think about milk supply, milk removal is the most important thing. Things like lactation cookies or supplements might help some people, but consistently and effectively removing milk is key.