The Amazing Science Behind Breastfeeding: How Breast Milk Constantly Changes to Meet Your Baby's Needs
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Most people think of breast milk simply as food. But breast milk is so much more than just calories, fat, and protein, it’s a living and completely customized for your baby. Even after decades of research, we’re still discovering new things about how seriously remarkable it is.
This week, I wanted to give just a few reasons why breastfeeding is one of the most incredible biological processes that a woman's body can do.
Breast milk isn’t the same every day.
Your milk is constantly changing every day and adapting to exactly what your baby needs in real time.
In the first few days after birth, your body produces colostrum, a small amount of super concentrated milk that’s extremely rich in immune factors and perfectly matched to your baby's tiny stomach.
One of the biggest myths I hear is that your baby needs to be supplemented until your milk “comes in". Most of the time, that's simply not the case. Colostrum being produced in such small quantities is not a sign that your body isn’t making enough milk, it’s exactly what your newborn needs in those very early days. Because a newborn’s stomach is only about the size of a cherry on day one, those small amounts of nutrient and immune rich colostrum are usually the perfect amount for a healthy, full-term baby.
Over the next couple of weeks after delivery, your milk transitions into transitional milk and eventually mature milk. As your baby grows, the composition of your milk continues to adapt to support their changing and growing nutritional needs.
Your milk even changes throughout the day.
One of the most interesting findings is that breast milk has been shown to follow your body’s natural daily rhythm. Researchers have actually found that some components of breast milk naturally fluctuate over a 24-hour period.
For example:
- Night milk typically contains higher levels of melatonin, a hormone involved in sleep
- Morning milk typically contains higher levels of cortisol, which is associated with alertness
- Levels of certain fats, cholesterol, iron, and other bioactive components also change throughout the day
Scientists are still studying exactly how these changes affect babies, but they are thought to support the development of an infant’s own biological clock. While this research is still developing, accredited organizations like the ABM, CDC, and AAP do not currently recommend and state it is unnecessary to separate pumped breastmilk according to when it was pumped (AM vs. PM).
Breast milk is packed with so much more than just nutrients.
Breast milk contains thousands of active ingredients, biological components, immunological factors, and even protective elements. Some of these include:
- Antibodies
- Immune cells
- Human milk oligosaccharides (HMOs)
- Hormones
- Enzymes
- Growth factors
Together, all of these components help support your baby’s developing immune system, digestive system, and overall growth. And because breastmilk is a living substance, the nutritional and bioactive components change with every feeding.
Breastfeeding has so many short and long term benefits for both mom and baby
One of the most incredible things about breastfeeding is that many of its benefits extend way beyond the newborn stage. Breast milk isn’t just a source of nutrition, it’s also associated with important health benefits (when compared to the alternative i.e. formula feeding) for both babies and mothers, many of which can last well into adulthood.
For babies, some of the benefits of breastfeeding include:
- A lower risk of ear infections
- A lower risk of GI & respiratory infections
- A reduced risk of Sudden Infant Death Syndrome (SIDS)
- A dramatically lower risk of necrotizing enterocolitis (NEC) in preterm infants
- A lower risk of childhood obesity
- A lower risk of developing type 1 & type 2 diabetes
- A lower risk of certain childhood leukemias
- A lower risk of developing crohn’s disease and ulcerative colitis
Breastfeeding has also been shown to benefit the breastfeeding mother as well. Research has found that breastfeeding is associated with:
- A lower risk of breast cancer
- A lower risk of ovarian cancer
- A lower risk of type 2 diabetes
- A lower risk of high blood pressure & cardiovascular disease
- Faster uterine involution after birth (the uterus returning to its pre-pregnancy size) in the early postpartum period
*It’s important to remember that these are reduced risks, and not guarantees. Breastfeeding doesn’t eliminate the possibility of developing these conditions, and not breastfeeding doesn’t mean they will occur. Overall health is influenced by many factors.
Scientists are still learning about breastfeeding and breastmilk specifically.
Despite everything that's already been discovered, researchers continue to discover new things about breast milk. That’s one of the reasons breastfeeding research is so exciting, because there's still so much we don’t fully understand yet. The more we learn, the more we realize that breast milk is so much more complex than simply “food" for your baby.
A gentle reminder
Whether breastfeeding has been easy for you, incredibly challenging, or somewhere in between, I want to leave you with this: your body is capable of extraordinary things!
And if breastfeeding didn’t go the way you hoped, that doesn’t take away from everything you’ve done to love, nourish, and care for your baby. No matter what your feeding journey looks like, you’re doing an amazing job.
References
Amitay, E. L., & Keinan-Boker, L. (2015). Breastfeeding and childhood leukemia incidence: A meta-analysis and systematic review.
Meek, J. Y., & Noble, L. (2022). Technical report: Breastfeeding and the use of human milk.
