My partner believes that it is beneficial for our baby to be given expressed breast milk at the same time of day that the milk was expressed, e.g. breastmilk expressed in the evening would ideally be given in the evening of another day.

Her reasoning for this is a belief that breastmilk changes depending upon the time of day it is produced, so breastmilk produced at night will contain a different chemical mix which will be more likely to encourage a baby to sleep for example.

Is there any evidence to support this?

1 Answer 1


According to the study titled The possible role of human milk nucleotides as sleep inducers published in Nutritional Neuroscience, a link was found between certain levels of nucleotides contained in breast milk over a 24 hour period.

The conclusions portion stated the following:


The assay of nucleotides in the breast-milk of the study population showed that their levels were not constant over a 24-h period. This was particularly so for 5′AMP, 5′UMP, and 5′GMP, which showed increased concentrations at night and may, therefore, be involved in inducing hypnotic action in the infant.

For a link to the full study, click here


I'd like to clarify some misinterpretations that seems to be occurring. The intent of me posting the paper and referencing it was to show that breast milk changes throughout the day. The paper does not prove that this induces sleep for babies but only states that it is possible (note the title of the paper). Please do not misinterpret this. OP's partner is partially right and partially unproven.

Yes, breast milk seems to follow a circadian rhythm. It is not clear if these chemical changes induce sleep in the receiving baby.

  • Comments have been moved to chat. May 30, 2018 at 4:13
  • 4
    Of course, my partner HAS interpreted this as her being right :)
    – AGB
    May 30, 2018 at 10:14

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