Meg asks about the rationale for switch feeding in cases of low
supply.  Applying Peter Hartmann's findings to milk synthesis and milk
ejection it can be a challenge to see how and why it works.
When the milk supply is low there is less and less milk being moved down
with each milk ejection if you are to stay on one breast.  To keep the baby
interested and happy switching breasts will give him more milk sooner.
Peter Hartmann also reports that while the infant is feeding at the breast,
milk synthesis in that breast is virtually non-existent.  So long,
lingering feeds on one breast mean long periods of time where no milk is
being synthesised in that breast.  We know that it is the decreased volume
of milk and hence the decreased presence of the FIL (that small whey
protein) which is directly related to milk synthesis.  By switch feeding as
the volume in the first breast (breast A) gets to fairly low and baby moves
to the slightly fuller breast (breast B) milk synthesis kicks in at a much
faster rate (in breast A) than it had been doing in breast B.  Then as that
volume drops (in B) it's back to breast A again and milk synthesis in B
will begin much faster than it had been previously.

Gonneke mentions the effect of prolactin.  Prolactin has, apparently, no
effect on breastmilk synthesis.  It is essential as a component of
breastmilk and without it breastmilk doesn't get made, but the serum levels
of prolactin don't influence the volume of milk synthesised.  This is
demonstrated by the falling levels of prolactin over the first few months
despite maintaining breastmilk production at about the same volume until
demand by the infant starts to fall.

How and why do we see such dramatic results in some women when they take
galactagogues which increase serum prolactin levels?  I guess because they
are the fortunately small number of women whose prolactin levels just dip
down too low to be able to provide that substrate of prolactin necessary
for milk components.

Denise

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Denise Fisher MMP, BN, IBCLC
BreastEd Online Lactation Studies
http://www.health-e-learning.com

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