Breast milk is widely known as a source of essential nutrients and immune protection for babies. But breast milk holds another secret—a natural biological clock that regulates an infant’s sleep, metabolism, and immune system from birth.
New research shows that breast milk is not just food; it’s a signal passed from mother to child that regulates the newborn’s circadian rhythm (the sleep-wake cycle). This discovery may change our attitude toward pumped milk and allow us to tailor feeding times to an infant’s biological clock, which will significantly improve their health.
Study Details:
The study found that the composition of breast milk changes throughout the day to transmit important hormonal and immune signals to the infant, in sync with the mother’s circadian rhythm. In samples taken over a 24-hour period, researchers found that hormones like melatonin and cortisol varied throughout the day. Melatonin (the sleep hormone) peaks around midnight, while cortisol (a metabolic regulator) is highest in the morning. These natural fluctuations in breast milk help infants develop their own day-night cycle.
This discovery is important because many mothers pump and store milk for later feedings. This common practice may be unintentionally disrupting these biological signals if the milk is used at the “wrong” time. Feeding with pumped milk according to the time it was collected (morning milk in the morning, night milk at night) may help infants better establish their biological clock, which will have a positive effect on their sleep and overall health.
The study showed that the composition of breast milk changes as the child grows. For example, the levels of immune proteins, such as lactoferrin and immunoglobulin A, are highest in the first month of life, which helps protect the newborn’s immature immune system.
Notably, a mother’s body mass index (BMI) affects the hormonal changes in her breast milk: milk from obese mothers showed less hormonal variation, which indicates that the mother’s health affects the natural “chronological signals” passed on to the infant.
In addition to hormones, researchers also studied the microbial composition of the milk. Although the microflora remained relatively stable throughout the day, differences were found in the types of certain bacteria between morning and night. These microbes play a vital role in gut health and the formation of immunity.
Although this research shed light on the complex and time-dependent nature of breast milk, the authors note that it also has some limitations, including a relatively small study population. Therefore, more extensive and diverse research is needed. Future studies will investigate how irregular feeding times affect infant development and how labeling pumped milk with collection times can optimize desired outcomes.
Source: Frontiers in Nutrition
