I'm going to take a stab at this one.
There are two different issues re: exogenous iron and the breastfed
baby.
#1- Giving any other food reduces the ability of the infant to absorb
iron from breastmilk.  The balance of nutrients in breastmilk is such
that it optimizes the absorbtion of all nutrients.  Giving anything else
disrupts this perfect balance and changes the absorbtion of many
different nutrients.  Iron absorbtion has been well studied, because it
is one of the more delicate balances.  Half of the iron in breastmilk is
absorbed, whereas 2-10% of the iron in cereal or formula or iron
supplements is absorbed.  If you are wasting 98% of the iron you are
taking in, you have to take a huge dose to actually get enough into the
body to meet your needs.  This brings us to:

#2- Iron is also necessary for the growth of many pathogenic bacteria.
Lactoferrin is an iron scavenger compound.  It absorbs all the iron that
is left over in the baby's intestines, and keeps it from being available
for bacteria to grow on.  But, lactoferrin can only absorb so much
iron.  It was designed to absorb the amount of iron that is left
unabsorbed from breastmilk, it was never intended to compensate for a 50
fold overdose in iron.  Once lactoferrin is saturated, that's it, it
can't absorb any more iron, leaving iron around to fuel the growth of
bacteria like e-coli, klebsiela, etc.

To make the issue even more complicated, low iron abm does have iron in
it, just not as large a dose as iron-fortified abm.  I usually recommend
that infants who are taking mostly human milk and are being
supplemented/complemented with abm get low iron abm, whereas if they are
only getting tiny amounts of human milk, they should get high iron abm.
This is based on my interpretation of the basic science studies on the
issue, and an attempt to balance the immune protection of breastmilk vs
the infant's need for iron.  Of course, if an infant is clinically
anemic, they should be supplemented.  I have previously posted citations
on lactnet of studies on this issue, they are in the archives.
--
Catherine Watson Genna, IBCLC  New York City  mailto:[log in to unmask]

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