Breast milk is dynamic--the amount of fat, antibodies and proteins adapts according to the baby's needs, mom's diet, and time of day. But Nighttime Breast Milk has a Super-Power: Melatonin! Melatonin is a hormone adults produce at night that makes you feel drowsy. As it turns out, breastmilk produced at night contains melatonin--making baby more drowsy and reducing colic. (Melatonin also relaxes the smooth muscles of the gastrointestinal tract, reducing colic.) Daytime milk has no detectable level of melatonin.
This bit of information could be critical for moms who are pumping--labeling and offering nighttime milk at night could help your baby sleep better! Meanwhile, this helps explain how breastfed babies sleep better than their formula fed peers. Incredible how moms' milk can help regulate a baby's circadian rhythm.
To read more about the studies: http://www.ncbi.nlm.nih.gov/pubmed/8370707
Postpartum Doula, Breastfeeding Counselor, Mother of Three.