What is melatonin doing in breastmilk?
Melatonin is a hormone secreted by the pineal gland, which sits in the back portion of the brain. Often referred to as our ‘third eye’, the pineal gland secretes melatonin in response to light exposure. Monkeying with light exposure, such as bedtime reading of screens that emit blue light, can disturb our rhythmic melatonin secretion, contributing to sleep problems. Getting up each morning and bathing oneself in sunshine helps to regulate our melatonin, and thereby our sleep/wake cycle.
Melatonin, present in breastmilk, contributes time-of-day information to infants by varying its concentration throughout the 24 hours. Other compounds in breastmilk also play a role in the circadian rhythm of infants, such as cortisol, tryptophan, leptin and others.
The researchers for this week’s CQW article sought to determine if freezing/thawing of expressed breastmilk has an effect on the concentration of melatonin in breastmilk. They studied melatonin concentrations in the expressed breastmilk from 13 women after the milk was frozen and defrosted. Measurements were taken at 1,2,3,4, and 24 hours after defrosting. They found that melatonin levels are stable for at least 4 hours and up to 24 hours after defrosting.
But, there are some other interesting things to know about melatonin, so go ahead and test yourself below.
Phyllis
I am wondering if these melatonin levels vary by the typical sleep-wake cycles of the lactating. For example, if the person who is producing/expressing milk works an overnight shift and therefore sleeps during the daytime, are the melatonin levels in that person’s milk on a different schedule than the patent who works in the daytime and sleeps at night?
And another application question: in the NICU, in order to maximize comfort and minimize inflammation, should we preferentially use milk that was produced during high melatonin times of day (3-7 AM in most cases)?
Anne Eglash
I suspect that melatonin levels would be the highest at different times for 3rd shift workers, as compared to first shift workers. Regarding the NICU question, it would seem logical to match the time of milk expression with the time of milk feeding.
andrea
This is fascinating! If you pump milk in the evening and give that higher melatonin breastmilk during the morning time on a subsequent day, would that disrupt the circadian rhythm? I breastfed and pumped, but never labeled my milk with the time of day.
Jeeannette
Hi, so what time should I Breast feed my baby so they can get some melatonin ?
IABLE
Your body naturally makes melatonin towards evening, as you are getting ready to go to bed. So, nursing your baby in the evening and over night provides melatonin in breastmilk
Anna
So does this mean that if my baby sleeps through the night and I pump first thing in the morning even if it’s at 7:30/8 am there will still be a higher concentration of melatonin in my breast milk from it being produced all night?
My husband is reluctant to give that milk to our baby right before bed because he knows breast milk contains melatonin and doesn’t want to disrupt baby’s sleep since the first feeding of the night determines how the rest of the night goes. Thanks!
IABLE
Hi, the melatonin level will be lower by morning, because it will move out of the milk as your blood concentration declines. Although we know that melatonin levels in breastmilk are higher before bed and in the middle of the night, we don’t know that it truly has an impact on infant sleep. No studies have been done to prove this. Melatonin also is a strong anti-inflammatory hormone, so that might be more of its role in breastmilk.