Human breast milk is much more than just a meal: it is also a clock that provides information to babies about what time of day it is, since the composition of breast milk changes throughout the day. In the morning the energizing milk contains a cocktail of ingredients different from the soothing milk of the night. Researchers believe that this "chronutrition" may help program the developing circadian rhythm of babies, the internal stopwatch that allows babies to distinguish day from night.
But what happens when babies consume milk that does not come directly from the breast and that has been extracted at other times of the day or has been saved for the baby to consume at another time? Until now, scientists had barely worried about studying the possible effects of "late" milk consumption on babies' development, but the repercussions may be very wide.
As psychologists who study paternity biology, we collaborate with Laura Glynn, Caroline Steele and Caroline Bixby to investigate breast milk tests as a measure of time.
Biological clocks throughout the day
Both sleep, digestion and energy levels show circadian rhythms, which means that they follow a daily cycle. As any parent who has had to get up at 3 in the morning to raise their baby knows, babies are not born with these rhythms completely synchronized. In turn, his sense of day and night develops during the first weeks and months of life thanks to signs such as sunlight and darkness.
In Babies and more Breast size does not influence milk production: we explain whyBabies can have very different behaviors: some show circadian fluctuations in quite predictable hormones in relation to alertness, sleep and appetite, being able to sleep for long periods of time shortly after birth, while others seem to have the rhythms Disrupted diaries for months. A delay in the development of the circadian rhythm can increase the risk of colic and lead to growth problems or malnutrition.
But scientists know very little about the reasons for differences in the circadian biology of babies. Breast milk may help program babies' circadian rhythm, which would help explain why some parents of newborns can sleep through the night, while others have a hard time getting their babies to get used to a routine.
Breastfeeding in the afternoon could cause the mother to give the baby signs that it is "bedtime."Milk changes
Breast milk changes significantly throughout the day. For example, cortisol levels (a hormone that promotes alertness) are three times higher in morning breast milk than at night. Melatonin, which affects sleep and digestion, can barely be detected in daytime milk, while it increases in the afternoon and reaches its maximum levels at midnight.
Nighttime milk also contains higher levels of some DNA components that help improve healthy sleep. Daytime milk, on the other hand, has more amino acids that encourage activity than nighttime milk. The iron in milk reaches its maximum levels at noon; Vitamin E in the afternoon. Minerals such as magnesium, zinc, potassium and sodium have all their highest levels in the morning.
Daytime milk may contain an entire immune mixture. Among the mothers who provided the scientists with breast milk samples during the first month after delivery, the immunological components (including key antibodies and white blood cells) had higher levels by day than at night. Another study found higher levels of an important component for immune system communication in daytime milk compared to nighttime milk.
In Babies and more How to help your baby sleep at nightAlthough it is clear that milk changes throughout the day, scientists still know little about the meaning it has for babies' health.
Researchers know that the hormones and immune components in breast milk are transmitted to babies and that babies begin to develop and refine their own circadian rhythms during the first months of life. It is plausible that these time-related signals in breast milk can help shape babies' own circadian biology. Differences in breastfeeding times could explain why there are so many differences in the development of these daily rhythms from one baby to another.
Messages in time in milk?
For most of human history, breast milk could only be consumed directly from the breast, which meant that milk would always be ingested when it was produced. Now, with breast pumps and refrigeration it is no longer the case: according to a survey carried out between 2005 and 2007, more than 85% of mothers who breastfeed in the US had taken out the milk.
What happens when babies are fed night milk in the morning or daytime milk in the afternoon? We don't know for sure, since there are hardly any studies about it. Giving a baby a bottle of daytime milk in the morning, with its high levels of cortisol and low levels of melatonin, could be the nutritional equivalent of turning on the lights just before bedtime.
If the temporary signals in milk really help calibrate the circadian biology of babies, then those who are fed milk "at the wrong time" may have more problems with sleep, digestion and development.
Controlling the time at which the milk has been extracted could help determine if there are problems in the circadian rhythm.Of course, there is a simple way to fix it. Mothers could label their breast milk with the time of extraction and coordinate the time at which they feed the babies in order to offer them milk in the morning in the morning, milk in the afternoon in the afternoon and milk in the afternoon. Nights at night.
If it happens to be the usual practice in intensive care units for newborns, we believe that thousands of babies could benefit from drinking milk at the right time, which could help them to have a better regulation of circadian rhythms. There are many intensive care units for newborns who have already adopted practices designed to improve the regulation of circadian biology in babies, such as lowering the lights at night, so that breastfeeding takes into account the time of Milk production would be the next logical step to follow. Similarly, milk banks that accept donor milk could classify milk in batches according to the time of extraction.
There is a simpler alternative to having to coordinate the milk that has been extracted: improve women's ability to breastfeed babies directly by improving the conditions of maternity and paternity leave. Mothers who can directly breastfeed their children do not have to worry about organizing milk for hours of the day and offering milk directly from the breast could have other health benefits.
Science continues to explore the role of breastfeeding in internal clocks and their impact on the health and development of babies. If the milk according to the time of extraction turns out to be a good way to establish the internal clocks of the babies, it is a matter of public health that reflects the importance of the creation of measures that help the mothers to stay at home with Your children during the first year of life.
Authors: Darby Saxbe. Assistant Professor of Psychology, University of Southern California. Dornsife College of Letters, Arts and Sciences; Y Jennifer Hahn-Holbrook, Assistant Professor of Psychology, University of California, Merced.
This article has originally been published in The Conversation. You can read the original article here.
Translated by Silvestre Urbón
Photos | iStochphoto
