Many mothers struggle to stay alert when nursing, particularly in the middle of the night. Some of the fatigue of mothering can be contributed to broken sleep; however, there is more to this topic than lack of sleep. Even during the day, a well-rested mother can feel particularly drowsy during nursing. As her baby grows full and sleepy, the mother may feel like taking a nap alongside her baby.
In the human body, there is a gastrointestinal hormone called cholecystokinine (CCK), and one of its jobs is to signal sedation and a feeling of satiation and well-being after eating a meal. During the act of breastfeeding, CCK is released in both the mother and the infant, and it produces a sleepy, satisfied feeling. The hormone prolactin, sometimes called the “mothering hormone,” also plays a role in helping many mothers to feel relaxed while nursing. Both CCK and the surge in prolactin in mothers frequently make a sleepy cocktail, too difficult to resist.
A La Leche League article on the content of human milk ( Myer 2006) states that:
The infant’s CCK level peaks twice after suckling. The first peak occurs immediately after the feeding. It peaks again 30 to 60 minutes later. The first CCK rise is probably induced by suckling; the second by the presence of milk in the GI tract. The drop of infant CCK levels 10 minutes after a feeding implies a “window” within which the infant can be awakened to feed from the second breast or to reattach to the first side for additional fat-rich milk. Waiting 30 minutes after the feeding before laying the baby down takes advantage of the second CCK peak to help the infant to stay asleep.
Along with important psychological bonding that makes mothers “in tune” with their babies, there are also other chemical connections between the mother and her infant. One type of physical communication begets the other, and the child and mother are connected on a very deep, personal level through both breastfeeding and the milk itself. A study by Kierson et al., (2006) concluded that the hormone ghrelin, but not CCK, is present in breastmilk. Ghrelin is reported to increase the appetite and promote the storage of abdominal fat, which is important to young growing children. The CCK that circulates in the mother is not shared with her baby; the baby makes his own CCK. The authors surmised that the hormone ghrelin was produced and secreted by the breast because ghrelin levels in breastmilk are higher than those found in plasma. The mammary gland appears to produce a ghrelin message which is transmitted to the baby.
In conclusion, it is difficult to identify why CCK would be released in mothers during breastfeeding. The research indicates that the evidence available has not focused on that question. We can, however, look at the possible reasons behind a biological necessity of the mother’s feeling satisfied, sleepy, and relaxed during nursing. Would she fall asleep and then be available for more nursing in 30 minutes? Does CCK release peripherally to promote harmony, pleasure, or bonding? What types of hormonal feedback make breastfeeding desirable to mothers?
Basque Research. (2009, 2012 web), Action of ghrelin hormone increases appetite and favors accumulation of abdominal fat. ScienceDaily, http://www.sciencedaily.com/releases/2009/05/090520055519.htm
Keirson, Jennifer A., et al. (2006, 2012 web), Ghrelin and cholecystokinin in term and preterm human breast milk. Acta paediatrica, 95: 8, 991-995. http://cat.inist.fr/?aModele=afficheN&cpsidt=17997348
Myer, S. (2006, 2012 web), What makes human milk special? La Leche League International, NEW BEGINNINGS, 23: 82-83. http://www.llli.org/nb/nbmarapr06p82.html
Nagin, M. K. (2009, 2012 web), Prolactin. About.com, http://breastfeeding.about.com/od/breastfeedingbasics/g/prolactin.htm
(c) 2010 Serena Meyer, IBCLC All Rights Reserved