>>I wrote, "For instance I have been measuring sIgA and lactoferrin (among
>>other things) in women with a perceived oversupply and their concentrations
>>of these components are significantly (statistically) higher than the
>>norm-not what I would have expected."

A response was
> I don't find that surprising or unexpected.  Why?  We know from various
> studies (Semba et al.) that these components are higher than the norm in
> colostrum and during weaning.  Thus, women who have a perceived (key word)
> oversupply of breastmilk are actually in a state of weaning.

The women I studied weren't in a state of weaning, I labelled it "perceived
oversupply" because I didn¹t measure milk production (no objective
measurable definition). I sampled these women (and lots of others without
"oversupply issues") over a period of three months post partum. These women
always felt they had full breasts, where always leaking milk, (you know that
feeling that mothers have, that they could feed the whole neighborhood) had
babies between 60-90th percentiles and continued to exclusively breastfeed
after their perceived oversupply resolved (at around 8 weeks for these
women).

>In fact
>I would say that often they are a sign of erratic nursing patterns or mothers
>who go too long between nursings.  The breast tissue is actually lowering
>production of milk because the mother is not nursing enough.

If, as you propose, their breasts are in a "state of weaning" because of the
fullness of the breast (ie a low rate of synthesis) you would then expect
them to experience a rebound low supply.  Even if there was so, the breast
does not "make" more immune components during weaning, the concentration
only rises because the volume drops.

BTW (as an aside) Not sure why you have referred to Semba. His work on
mastitis and immunological factors actually proposes  subclinical mastitis
as a cause for the high levels of immune factors found in his sample (he
hasn't specifically himself measured colostral and weaning secretion immune
factors - this was done by Peggy Neville, in much earlier work). With regard
to his subclinical mastitis/HIV work however it is important to note  he did
not measure milk production in this study , which can be negatively
influenced by energy deprivation from poor nutrition such as occurs in
developing communities (Malawi) and subsequently result in higher
concentrations of immune factors (although it is important to note
nutritional status has  not been found to directly effect the amount of anti
microbial proteins). He also didn¹t measure the presence of any concomitant
disease which may be important in his proposed model (and samples where only
taken from one breast and not linked to the existence (or not) of localised
breast symptoms).

>If we think about
>it there are actually 2 times during the lactation period that higher levels
>of immune components are really vital for the survival of the infant--the
>newborn period and during weaning.

Actually I would like to propose another theory - I don¹t believe that
natural weaning represents a threat to the infant - if weaning occurs
naturally according to biological norms (which is after several years) the
child is well established on a diet and their immune system is becoming well
developed. I think the increase in concentration in immune factors during
weaning is probably to protect the breast at a time when it is susceptible
to infection because with reduced volume the flushing mechanism of normal
milk volumes is lost.

>I agree with Heather that "immune components are going to differ between
>mothers, between babies and between feeds..."

There is certainly an individual variation within the norm (just as not all
women produce spot on the average 800mls/ 24 hours - they will fall
somewhere within the normal range) There is also is a normal range for
anti-microbial proteins- which does not change significantly (statistically)
in the short term (that is between foremilk and hind milk  or between feeds)
- in fact no milk components do, except for fat and prolactin.
Therefore when there is a statistically significant difference measured this
means their levels do not fall within the normal range (as was true for the
oversupply women I sampled).

I think oversupply is a significant problem for some women, and is not
necessarily a result of "erratic" feedings (especially prolonged oversupply
issues). I believe there may be a pathological mechanism involved - in that
the normal inhibitory mechanisms are not functioning as well as they should
(and this may well have to do with the developed world's change in feeding
style - ie less frequent larger feeds). For instance Cox et al (1996) found
there was a relationship between prolactin in milk and degree of fullness of
the breast - except in one women there was no relationship - she had an
oversupply problem that they hypothesised was due to a lack of response to
local feedback inhibition of milk synthesis.

Regards
Cathy Fetherston
Perth Western Australia

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