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Subject:
From:
Catherine Fetherston <[log in to unmask]>
Reply To:
Lactation Information and Discussion <[log in to unmask]>
Date:
Mon, 24 May 2004 14:16:03 +0800
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Hi Zena,
Below is a copy of a lactnet post from 2001 that I made to a very similar
question. As you can see this is a perennial question - I think because
there are so many myths surrounding this issue. Hope its helpful.

Cathy Fetherston RM PhD IBCLC
Perth, Western Australia


> Can you help me out here?  I was recently told that "research has completely
> debunked the whole idea of foremilk and hindmilk."  Now, I'm getting this
> second hand, so I wasn't able to ask for the specific research.  I know Peter
> Hartmann has done some work that has changed our understanding a bit of
> fore/hindmilk, but if someone could point me in the direction of legitimate
> research that states there is NO fore/hind milk, I'd appreciate it.

Hi Jan, It's not that there is NO hindmilk or foremilk, its that research is
now showing that our previous assumptions made about "emptying the one side
first is essential for babies to thrive" - based on the high fat hind milk
theory - is not true.

Foremilk (defined) is the milk that can be expressed from a breast prior to
a feed. Hindmilk is the milk that can be expressed from that same breast
immediately following the end of a feed.

Fat content in hindmilk is reliant on many different factors (including
parity, diurnal influences, individual variances and many more  - in fact
individual variance can be huge, eg 29g/L in one mother
vs 62g/L in another - yet both babies thrived).

However 70% of the variability of fat in milk is due primarily to two things
- the degree of fullness of the breast and the time elapsed since the
previous feed. The lower the degree of fullness of milk in the breast the
higher the fat content. Obviously this is relative to how much milk is taken
at any one feed as well as to WHEN the feed occurs (degree of fullness is
"generally" always less in the evenings and highest in the mornings)
Therefore on this basis the hindmilk at the end of a morning feed may in
fact have a lower fat level than the foremilk of a feed taken much later in
the day when the degree of fullness is very low. In addition to this if
there is a short time between feeds the fat has not had much time to adsorb
(stick to) to the duct walls and the fat content is relatively high compared
with when there is a long period between feeds and the foremilk fat will be
relatively low (compared to hind milk) because it has had a longer time to
adsorb to epithelium. With the increased flow from let down, fat is slowly
dislodged from the walls and combined with the higher fat milk from the
alveoli. This mixing of milk is why the foremilk in the second breast will
always be higher in fat than the foremilk in the first breast.

To add to these complexities women who have lower storage capacities and
therefore a more consistent degree of fullness over the period of the day
(than women who have much larger storage capacities) will probably have less
variation in fat content between feeds.

So to cut to the chase, research has shown that it isn't important how we
feed infants at any one given feed (eg finishing the first side first etc)
it is the volume that is received over a 24 hour period that is important
for infant growth. So basically I never give prescriptive advice about how
to feed, so long as babies get fed when they want to be fed (in whatever
mode suits the individual mother and baby) they will grow (excluding
pathology of course).

A good overview of the literature is:

Cregan M & Hartmann PE. 1999. Computerized Breast Measurement from
Conception to weaning: Clinical Implications. J Human Lact 15(2): 89-96.

More specifically:

Daly SEJ et al. 1993. Degree of breast emptying explains changes in the fat
content but not fatty acid composition of human milk Exp Physiology
78:741-55.

Butte NF et al.1984. Human milk intake and growth in exclusively breastfed
Infants J Pediatrics. 104: 187-95.

Mitoulas, LR, Kent, Hartmann et al. 2002. Variation in fat, lactose and
protein in human milk over 24h and throughout the first year of lactation
British Journal of Nutrition. 88: 29-37

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