Our circadian rhythm is our internal body clock.
It’s roughly a 24-hour physiological cycle, regulated by hormones made by our bodies. It can also be influenced by external cues such as sunlight and temperature.
The hormones regulating our circadian rhythm include cortisol, which helps us wake up and feel energetic during the day, and melatonin, which helps us fall asleep at night.
In breastmilk there are several components that also show a circadian rhythm.
3 Facts About Circadian Rhythm Of Breastmilk Components
More research is needed but it’s likely the circadian rhythm of at least some of these components enhances the wellbeing of breastfed babies.
Here are 3 facts about the circadian variation of breastmilk components.
#1: The Fat Content Of Breastmilk Displays A Circadian Rhythm
The fat content of breastmilk is typically higher during the day and the evening, and lower during the morning and at night.
#2: An Amino Acid In Breastmilk Could Help Breastfed Babies Sleep Better At Night
Breastmilk contains tryptophan, an amino acid used by the body to make the hormone melatonin. Melatonin helps induce and regulate sleep.
Levels of tryptophan in breastmilk increase and decrease according to maternal circadian rhythms. This suggests breastfeeding might help develop babies' circadian rhythm and help them settle to sleep better at night.
#3: Several Other Components Of Breastmilk Might Have Circadian Variability
Some studies have shown a circadian rhythm in the level of certain minerals (e.g. calcium, phosphorus and magnesium) in breastmilk. However, other studies found no significant variations in the amounts of these minerals.
Research shows several other micronutrients (e.g. some vitamins and iron) and hormones (e.g. cortisol and melatonin) also have circadian variability.
So why might it be important for these various components of breastmilk to show circadian variability?
More Research Is Needed
It’s not currently known what function (if any) circadian variation of the components in breastmilk might have. Neither is it clear whether there would be any inherent problem if these components didn’t show circadian variation, but were delivered at constant levels over the course of a day.
Researchers have speculated the circadian rhythm of various components of breastmilk might be of particular importance for babies born prematurely.
From birth, exposure to daylight and maternal signals (including those in breastmilk) provide circadian stimuli to babies. Babies in the NICU are significantly less exposed to such daylight and maternal signals.
Therefore, it’s possible premature babies in the NICU could benefit the most if they were given expressed breastmilk matching the circadian phase in which it was expressed.
More research is needed!