Tuesday, August 2, 2011

Breastfeeding doesn't follow the Laws of Thermodynamics

Something has bothered me since the NICU and I'm wondering if someone has an answer.  In the NICU, they said the typical breastmilk contained 2/3s of a calorie per milliliter or 20 calories per ounce.  They also said the average woman makes around 30 ounces a day.  All seems reasonable, right?  Add in a third factoid that it is important to get an extra caloric load of 200 to 500 calories. 

This would seem to say that the average woman produces about 600 calories of breastmilk a day.  And that is 600 calories contained within the milk without accounting for any calories used in the creation of the milk.  This is HIGHER than the 500 calories they give as the high end of the caloric load.

I recognize they were just trying to get some basic facts in with a pumping log, but this seems to clearly violate the laws of thermodynamics.  Breastfeeding mothers as perpetual motion machines? 

My guess is that these amounts are due to an assumption that lactating mothers will also draw upon their maternal stores.

Other interesting trivia fact: based on this, I've produced 190,000 calories worth of breastmilk just counting the amounts that have been pumped and logged, excluding direct breastfeeding and the first two weeks that I don't have my pump log for.


  1. Maternal stores, it has to be. When I was both breastfeeding and pumping enough to feed a small infant army, I lost weight like you wouldn't believe. Baby weight? Gone in four weeks. Not that it was necessarily a GOOD thing to lose weight so fast, but I definitely had a calorie deficit that was observable in bodily changes.

  2. Definitely comes from fat stores, at least in typical cases. My butt, arms and legs are all noticeably thinner than before I was a mom. Also, at the height of my twin pumping days, I was eating way more than just 500 extra calories!