The Supply Shift | Demand and Supply
Alright friends, let's talk about Supply and Demand...or more accurately DEMAND and SUPPLY. Yes, it is the same concept so why do we want to emphasize the difference in wording? Let's discuss some basics about milk production.
What do we know? Let's talk about the role of hormones with our milk supply.
In the first days postpartum, our hormones are surfing on autopilot controlled by our endocrine system (glands in charge of hormone production / communication) (1, 2). After we deliver the placenta, the progesterone and estrogen levels that were high during pregnancy and inhibited lactation start to drastically come down allowing the body to kick up the milk production and secretion (1). Our prolactin levels, that were also elevated during pregnancy, are now able to communicate to the body to allow prolactin to do its job (1). If you recall from our physiology of lactation post, prolactin is the hormone responsible for milk synthesis!
As this is happening, our body starts gradually transitioning off of that early autopilot endocrine response and into an autocrine response (2). Autocrine control means our milk supply is under a localized control and now the breast communicates what we need rather than the hormones (2). The breast becomes the localized commander for milk production.
In order to tell our breasts how much milk they need to produce, two main steps need to take place:
1. We have to trigger communication from brain to breast through sucking/stimulation.
Why? Because the more stimulation and sucking at the breast, the more signals our brain gets to promote milk production by increasing prolactin levels and prolactin receptor sites (1). Receptor sites are important to explain here. What this means is in those early days and weeks, when we are setting up the foundation for our long term milk production, every time baby nurses our body makes more receptor sites - think of receptor sites as little holes and when prolactin is flowing through our bodies they land in these holes and they send signals to our brain, the more holes filled up with prolactin the stronger and more effective that signal is. So, we want to trigger communication through nursing so prolactin can spike and rush through our body AND we want to make loads of these prolactin receptor sites to maximize our body's ability to communicate. Got it? Let's move on to step two.
2. We have to drain milk from the breast.
Why? If we leave too much milk in the breast, it prevents the breast from communicating that we need more milk (1). That sounds pretty simple right? More specifically, there is a polypeptide protein in our breast milk known as FIL (feedback inhibitor of lactation) (3, 4). FIL tells the body we either need more milk or we have enough based on how much milk we're leaving in the breast. As our mentor, Gini Baker, IBCLC likes to say "You have to take FIL out, to fill up!" So in order to tell the breast to keep the milk coming, we need to empty it with each nursing session. Now, this doesn't mean nothing will come out of your breast by the end of the nursing session - your breasts will have milk even if you've nursed for hours straight. This simply means we need to drain the breast enough by allowing baby to nurse on demand without time restrictions, so we can allow the breast to communicate that it still needs milk production.
Enter the DEMAND and SUPPLY concept. We have to DEMAND milk for our body to know to SUPPLY it.
With frequent nursing and proper milk drainage, baby is able to drain FIL out, which signals to the brain to maintain/increase milk production keeping your supply strong and changing upon the needs of your baby (4)! This is why growth spurts and nursing at night are positive things - your baby is talking with your body and asking for more milk to keep up with baby's growth. Remember, for those first 6 months they're growing because of YOU and allowing them to dictate how much milk they need ensures your body keeps up. Trust your baby, trust your body. You've got this.
Breast, baby and brain communicate in a pretty sophisticated fashion. We start out on autopilot with the hormones doing most of the work for us. Nursing often in those early days has many roles for mom and baby - one of those important roles is to increase prolactin receptor sites. This becomes important once we transition from the hormone-driven milk production to breast-controlled production during which we have to demand the milk for our body to know to supply it.
So, what's the take-away? Follow baby's cues, nurse on-demand, and throw out timed feedings to make sure you're establishing a solid supply and that your baby is getting enough milk. If you're ever in doubt about whether your baby is getting enough milk, watch weight gain, track diaper output and reach out to an IBCLC for help.
(1) Lauwers, J. & Swisher, A. (2015). Counseling the Nursing Mother: A Lactation Consultants Guide. Burlington, MA: Jones & Bartlett Learning.
(2) De Coopman, J. (1993). Breastfeeding after pituitary resection: support for a theory of autocrine control of milk supply? J Hum Lact, 9(1), 35-40
(3) Love, S. & Lindsey, K. (2010). Dr. Susan Love’s Breast Book (5th ed). Cambridge, MA: Da Capo Press.
(4) World Health Organization. (2009). The physiological basis of breastfeeding. Infant and Young Child Feeding: Model Chapter for Textbooks for Medical Students and Allied Health Professionals. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK148970/