I want to share a communication from Mark Cregan, a member of the Hartmann
team, and the principle author of the prolactin article:
Cregan MD, Mitoulas LR and Hartmann PE. Milk prolactin, feed volume and
duration between feeds in women breastfeeding their full-term infants over
a 24 h period. Ex Physiol 2002; 87(2)" 207-214. Let me say that Denise
Fisher, of Health-E-Learning, deserves all the credit for Dr. Cregan's
response, as I was enrolled in one of her classes and she contacted Dr.
Cregan on my behalf.

I had a question on when hindmilk was snythesized...I thought that perhaps
hindmilk was just left-over foremilk that had not been removed. I recalled
reading that fat had a tendency to stick to the sides of collection
bottles, and wondered if there was a similar mechanism at work within the
breast, in that when the breast was significantly emptied, only then did
the fat release and become available to the infant.

Dr. Cregan answered (4/27/2004) (quote)
"Indeed, Niki almost got it right. The variation in fat content is not
related to synthesis, but rather the fact that fat 'sticks' to the ducts as
milk is ejected from the breast and thus it travels slower. As such at milk
ejection the aqueous components depart from the breast earlier than the
fatty components, creating low fat milk in the fore and high fat milk in
the hind. This has nothing to do with the synthesis. Indeed fat synthesis
is likely to have been at its greatest immediately after a feed when the
breast is most drained of milk. Thus, as with prolactin, secretion is
highest in an empty breast. But in the case of fat, the stickiness of fact
to the ductal cell membranes creates a gradient and thus a 'perceived'
difference in synthesis." (unquote)

I know this has been discussed at length in the archives, but felt that you
might all benefit from Dr. Cregan's simple, yet thorough explanation. Many
thanks to Denise, who made my enlightenment possible.

Niki Konchar, IBCLC

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