"Sleep Inducers" in Breastmilk Change over 24-Hour Period


Sánchez, Cristina L.; Cubero, Javier; Sánchez, Javier; Chanclón, Belén; Rivero, Montserrat; Rodríguez, Ana B.; Barriga, Carmen. "The possible role of human milk nucleotides as sleep inducers".
Nutritional Neuroscience Vol. 12(1):2-8. 2009.

As reported at PHYSORG.COM

Breast milk contains various ingredients, such as , which perform a very important role in regulating babies' . The new study, published recently in the journal Nutritional Neuroscience, confirms that the composition of changes quite markedly throughout the day.

The scientists looked for three nucleotides in breast milk (adenosine, guanosine and uridine), which excite or relax the central nervous system, promoting restfulness and sleep, and observed how these varied throughout a 24-hour period.

The milk, collected from 30 women living in Extremadura, was expressed over a 24-hour period, with six to eight daily samples. The highest nucleotide concentrations were found in the night-time samples (8pm to 8am).

"This made us realise that milk induces sleep in ", Cristina L. Sánchez, lead author of the article and a researcher at the Chrononutrition Laboratory at the University of Extremadura, tells SINC.

"You wouldn't give anyone a coffee at night, and the same is true of milk - it has day-specific ingredients that stimulate activity in the infant, and other night-time components that help the baby to rest", explains Sánchez.

In order to ensure correct nutrition, the baby should be given milk at the same time of day that it was expressed from the mother's breast. "It is a mistake for the mother to express the milk at a certain time and then store it and feed it to the baby at a different time", points out the researcher.

The benefits of breast milk

The World Health Organization (WHO) says breast milk is the best food for the newborn, and should not be substituted, since it meets all the child's physiological requirements during the first twelve months of life. It not only protects the baby against many illnesses such as colds, diarrhea and sudden infant death syndrome, but can also prevent future diseases such as asthma, allergies and obesity, and promotes intellectual development.

The benefits of breastfeeding also extend to the mother. Women who breastfeed lose the weight gained during pregnancy more quickly, and it also helps prevent against anemia, high blood pressure and postnatal depression. Osteoporosis and breast cancer are also less common among women who breastfeed their children.


  1. I do not believe what has been told to me by a friend who was given advice to not breast feed after one year, that the nutritional benefits are no longer in the milk supply. Even though I believe that feeding my toddler has many benefits outside nutrition, I am curious as to the reason this was advised and is there any truth to diminished benefits after one year?

  2. I'll pop in and reply that there is absolutely NO TRUTH to what your friend said about breastmilk having no nutritional benefit after a year. In fact, breastmilk continues to change and form to the new needs of an active toddler as he or she grows. There was a study that showed that the immunological properties of breastmilk actually increase with the duration of toddler breastfeeding. So as the toddler gets older and starts to have more interactions with a lever group of people and other children, he it she is more protected from the bacteria and viruses in his or her environment. I think I read about that in kellymom.com. They have a great section on nursing toddlers.

    In addition to the nutritional and health benefits, the developmental and emotional benefits of a natural term breastfeeding relationship are immeasurably wonderful. I wrote about nursing my 2 year old and my hopes for a change in the way our culture sees natural term nursing at my blog. Http://little-willa-lamb.blogspot.com. It was in the middle of November. Titled "why should I call it extended?"

    Really really neat about the nucleotides changing with the time of day! Too cool! Just goes to show you how smart our bodies are, to make such an entirely awesome fio for our children!



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