How Does Breastfeeding Work – Part 2

As you breastfeed your baby and ponder the meaning of life, you may also wonder to yourself “how does breastfeeding work?”  Truth be told, it is a complex and miraculous process of the female body.  As we discussed yesterday, lactation begins as a hormonal function.  Today we’ll discover that breastfeeding quickly becomes a labor of love based on supply and demand in part 2 of our series on how does breastfeeding work.

Once your milk supply is fully in, the name of the game is supply and demand.  The more the breast is stimulated and emptied, the more milk you will produce.  Here’s how it works:

how does breastfeeding workWhen your baby latches and starts stimulating your breast, two hormones are released: prolactin and oxytocin.  Both are essential for milk production.  Prolactin receives nutrients from your body via your blood to produce milk.  Oxytocin contracts the cells in the mammary glands to push milk out of the nipple and into your baby’s mouth.  This is known as the milk ejection reflex or let-down.

Mammary glands are made of channels where milk travels called milk ducts and alveoli, a group of tissues that secrete milk.  Inside the alveoli are cells that produce milk called lactocytes.  On lactocytes are prolactin receptors that have the ability to signal the production of breast milk.  To make milk, the hormone prolactin must meet its receptors to get the party started.  When milk fills the alveoli, the shape of the walls change and blocks the receptors so the signal cannot be given to make more milk. More receptor sites mean more potential milk production.  Researchers believe frequent breastfeeding in the first few weeks after childbirth can increase prolactin receptors.

Additionally, breast milk contains Feedback Inhibitor of Lactation or FIL that helps maintain milk supply.  When the breast is full of milk and therefore FIL, breast milk production slows.  Conversely, when the breast is drained and FIL is not present, production is stimulated again.

Both prolactin receptors and FIL work on a supply-and-demand basis.  Therefore, if you feel your milk supply is low, breastfeeding more often to drain your breast will cause your body to automatically refill it.  Women are often mistaken about breast size and milk supply.  Women of any size breasts can produce adequate milk for their babies.  Moms with smaller breasts may drain them faster but they will regenerate milk as long as breastfeeding continues.  Women with larger breasts may be able to store more milk at one time.

Breastfeeding is an amazing biological and emotional experience.  Now that you know how breastfeeding works, use this knowledge to your advantage for successful breastfeeding.

Did you know…

  • Let-downs can occur when you think about your baby, when you hear your baby or another baby cry, or when it is a normal feeding time.
  • You have multiple let-downs during every feeding although you may not feel them at all.
  • One study indicated that babies only drink about 75% of their mother’s milk in a day.
  • Breast milk production can continue indefinitely if breasts continue to be stimulated.
  • Substances enter breast milk through the bloodstream as it flows past the mammary glands.

Sources:, LaLecheLeague and Sutter Health