Hi Nikki
Am posting straight to lactnet with the hope that this appears in
English and not in computer heiroglyphics as it does on my computer.
Sort of yes, to all questions (with a little qualification). However
before I explain this a bit further I want to emphasize that none of
this is of any importance in regard to wt gains in babies and I would
like to re emphasize it is the volume of milk taken by an infant that
is related to growth not what's in the milk, be it fat, protein,
lactose or total energy  (VLBW excepted).

Nikki asked
> -----------------------------------------------------------------------------
> "The emptier the breast, the higher the fat content of that sample."
>
> My confusion comes with the "emptier the breast (low degree of fullness) the
> less variation in fat content between fore and hind milk."
>
> Does this mean that the higher fat in the sample from the emptier breast has
> a relatively constant fat content?
>
> Does this mean a fuller breast has a larger variation in fat content between
> the fore and hind milk?
>

 the qualification for the Yes answer relates to the volume of milk
taken by the baby at a feed. First I would like to paraphrase from a
paper by Leon Mitoulas et al. British J of Nutrition 2002, 88.
Variation in fat, lactose and protein in human milk  over 24h and
throughout the first year

"The fat content of fore and hind milk samples obtained from an
irregular feeding pattern from breasts with larger storage capacities,
varied more than those for more regular feeding patterns with smaller
storage capacities".

I will give two  examples that I hope will explain this.

If we take two mothers, one (MA) has a large storage capacity (eg 50%
of her infants daily intake) and another (MB) has a lower storage
capacity (20% of her infants total daily intake).

Because MA has a large storage capacity her baby has the option of
consuming  large volume feeds less frequently (eg. the 4 hrly feeding
baby) in order to consume his daily volume (eg 800mls)
Whereas MB will need to feed more frequently in order to consume the
same daily intake.
.
Baby of MA takes a large volume (150ml)  feed. Fat content in the
foremilk is 20g/L and at the end of the feed the hindmilk is 60g/L
Later in the day the fullness of the breast is less (as generally
fullness of the breast  decreases over the period of the day). Because
of this the foremilk fat is now higher than the foremilk of the
earlier feed, say 50g/L ( sometimes the foremilk fat can even exceed
that of the hindmilk fat from a feed earlier in the day) and baby
decides to take a smaller feed (60ml), hindmilk fat is say 68g/L. the
variation between foremilk and hindmilk is less because less volume
was taken, but the foremilk is higher in fat than the previous
foremilk sample because now the degree of fullness is less.

Baby of MB must take lower volume feeds due to lower volume available
at each feed, generally these babies take a consistant amount at each
feed (emptying the breast) and the degree of fullness is quite low at
the end of every feed. The variation between her foremilk fat (23g/L)
and her hindmilk (39g/L) is lower because there is a lower volume
taken. Because this baby takes more frequent lower volume feeds there
is less variation in fat concentration between fore and hind milk than
for the baby who takes larger and more irregular volumes (the
variation will be greater)

general principles are
1. the emptier the breast (lower degree of fullness) the higher the
fat content (relatively)
2. the smaller the volume taken at a feed the less variation in
concentrations of fat between fore and hind milk
3. You shouldn't  be comparing fore and hindmilk fat between women at
any one feed because of varying storage capacities, varying volumes
taken by babies (due to apetitie differences as wll as milk vailable)
and individual variation in fat content in their milk
3. none of this matters because over the course of a 24hr period the
differences between foremilk and hindmilk, and between feeds, even out
and the amount of fat recieved by an individual infant day by day is
relatively constant (with a large variation between mothers being
normal).

Sorry this has been so long, much easier to explain with graphs.

Regards
Cathy Fetherston RM PhD IBCLC
Perth, Western Australia

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