Nobody Told Me About Nighttime Breastmilk
Photo by Ayla Meinberg on Unsplash
Mother’s Day just passed, and, in honor of the day, there was an increase in the motherhood-focused content floating around. That’s how I came to learn that breastmilk is far more complex than I’d ever considered.
I understood breastmilk to be incredibly nutrient-dense, containing crucial macronutrients, micronutrients, and bioactive compounds and I understood that its contents vary across a baby’s development (colostrum vs mature milk) to meet changing nutrient needs. But what I didn’t know was that breastmilk contents also appear to shift throughout the day: nighttime milk tends to contain more melatonin and other compounds associated with sleep, while morning milk tends to contain more cortisol and compounds associated with alertness. The mother’s circadian rhythm appears to be reflected in her milk, meaning breastmilk may provide time-of-day cues that help support the baby’s own developing circadian rhythm.
There are so many questions and implications here to untangle, but my thoughts immediately went to the fact that a significant portion of breastfeeding mothers don't feed directly. We often pump, store, and feed later. Survey data of breastfeeding mothers found that 85% fed their babies previously expressed milk, 25% fed expressed milk daily, and 6% used expressed milk exclusively [1]. Which means a lot of babies may be routinely drinking milk produced at a completely different time of day than when they’re consuming it.
So are we sometimes unknowingly giving babies cues that it’s time to wake up right before bed?
I feel it goes without saying that understanding this better has real value for improving quality of life. New mothers are among the most sleep-deprived people on the planet, and the research on what that does to physical and mental health is not subtle. Plus, we aren’t talking about optimizing some marginal wellness variable. We’re talking about sleep during one of the most physiologically demanding periods of a woman’s life, when recovery, health, quality of life, breastfeeding success, and infant care are all intertwined. If mistimed feedings of expressed milk meaningfully disrupt infant sleep, there are direct costs to the baby and mother. And a mother's health has impacts far beyond herself. Flying cars sound cool, but I'm more interested in a future where new mothers get adequate sleep.
When I started mentioning this to people around me, I was surprised to find that some already knew and were carefully time-stamping their milk to match the right feeding window. But this information clearly hasn't reached most people. I hadn't encountered it even while breastfeeding my own child.
So why hadn't I heard about this before?
The research on breastmilk composition and the potential consequences of mistimed milk is still young, and I’m comfortable saying there is more that we don’t know about breastmilk than we do know. Sadly, research around women’s health remains underfunded, under-prioritized, and under-communicated. But what's already established about the complexity of breastmilk is striking enough to take seriously, and one of the most straightforward paths toward that is simply making sure more people know about findings like these.
And who could be a more fitting community to have this conversation than Women in Nutraceuticals? The complex, time-varying composition of breastmilk is exactly the kind of thing our industry is equipped to appreciate. Whether the next step is better research or simply asking better questions about the substances we consume and recommend, this community has a meaningful role to play.
1. Hahn-Holbrook, J., Saxbe, D., Bixby, C., Steele, C., & Glynn, L. (2019). Human milk as "chrononutrition": implications for child health and development. Pediatric Research, 85:936-942. https://doi.org/10.1038/s41390-019-0368-x
