Melatonin, known as a “sleep hormone,” regulates the body’s sleep-wake cycles. This hormone is naturally present in human breast milk, serving as a biological signal from mother to infant. Its inclusion helps establish early developmental patterns in newborns.
The Melatonin Cycle in Breast Milk
Melatonin follows a distinct circadian rhythm in breast milk, mirroring the mother’s internal clock. Levels are lowest during the day and begin to rise in the evening. Melatonin concentrations reach their highest levels during nighttime hours, peaking between midnight and 3-5 AM.
The mother’s body produces melatonin, which then transfers into her breast milk. For instance, melatonin levels at 3 AM can be nearly ten times higher than those in milk collected during the afternoon. This natural fluctuation means breast milk composition changes throughout the day, providing varying hormonal signals to the infant.
Influence of Maternal Circadian Rhythm
A mother’s sleep-wake cycle and light exposure directly impact the melatonin rhythm in her breast milk. The pineal gland secretes melatonin in response to light. Regular exposure to natural light during the day and darkness at night helps regulate the mother’s melatonin production, influencing levels transferred to breast milk.
Artificial light, especially blue light from screens, can disrupt melatonin secretion. Limiting exposure to these light sources before sleep supports natural melatonin production. A consistent sleep schedule helps maintain a stable circadian rhythm, ensuring rhythmic melatonin levels in breast milk.
Implications for Infant Sleep
Melatonin in breast milk is important for infants, as babies do not produce their own melatonin rhythmically for several months after birth. This transferred melatonin acts as an external cue, regulating the baby’s developing sleep-wake cycles. Consuming melatonin-rich nighttime breast milk helps babies sleep better and establish their own circadian rhythm.
Before babies develop their own melatonin production, they rely on breast milk for this hormone. Daily fluctuations of melatonin in breast milk help infants differentiate between day and night, contributing to a structured sleep pattern. This “chrononutrition” from breast milk helps synchronize the infant’s biological clock with the external environment.
Practical Tips for Mothers
Mothers can optimize the melatonin content in their breast milk to aid infant sleep patterns. Maintain a consistent sleep schedule and ensure adequate exposure to natural daylight to support melatonin production. Limit exposure to artificial light, especially blue light from electronic devices, in the evening hours before bedtime to enhance nighttime melatonin levels.
If expressing breast milk, label it with the time of day it was pumped. This allows for feeding the milk at a corresponding time, ensuring the baby receives appropriate hormonal signals—morning milk during the day and nighttime milk at night.