Breast milk is a clock. It communicates time-of-day to your baby chemically — perfectly aligned with the circadian rhythm of your body, the microbes in your gut, and the natural world.
Breast milk is so much more than a food. The deeper science digs, the clearer it becomes that we are only scratching the surface of the benefits and synchronicity of this amazing fluid.
From nutrients, immune factors and stem cells, to living microbes and the oligosaccharides that feed them, its' clear that breast milk is like no other fluid on earth.
Circadian rhythm 101
Our internal body clock is crucial to our health. It regulated by light exposure, temperature and food timing, as well as a variety of other factors.
The microbes in and on our bodies have their own circadian rhythm, which operate in a two-way relationship with our own. When your circadian rhythm is in flow with the natural world, sleep, energy and general health improve.
Babies are born without their circadian rhythms fully set, and start to find their early cycles in the first months of life. Basic environmental cues like light and darkness (bright/blue in the morning, dim/red at night), and temperature (warmer in the day, cooler at night) help set them.
Early research has shown that breast milk has a key role in this circadian 'setting' process for infants, through complex chemical messages which vary by time-of-day.
Morning vs. evening milk composition
Day milk also has more immune focused components, like antibodies and white blood cells, along with minerals like magnesium, zinc, potassium and sodium. Iron peaks around noon.
While some of the implications of these shifts are unclear, it appears very likely that breast milk provides a type of time-based communication with baby, which scientists call 'chronosignaling'.
Pumping and labelling by time-of-day
If like the majority of Australian women, you're pumping milk, it's worth considering labelling it with time of day (even if it's just AM and PM).
Feeding your baby with sleepy 'melatonin' milk in the morning, and energising 'cortisol' milk in the evening, may be the biological equivalent of switching on bright lights at bedtime.
Where possible, feed babies with stored milk from a comparable time-of-day, to reap the benefits of these nuanced 24hr fluctuations.
The bottom line
Humanity is yet to unravel the complex milk composition changes that occur in a single feed, across the 24hr circadian cycle, through the breastfeeding relationship, from mother to mother, and for different infants from the same mother.
The truth is, we may never fully understand the depths of this intricate design.
But your intelligent body understands it all, intuitively and viscerally. As did the women through all of human existence.
Just when we thought breastfeeding couldn't get any cooler 😉