Jung/Gaelicsheep - The iron that is in formula is non-haem iron (not animal based) and is extra difficult to absorb so more and more is added until enough is absorbed. Bm has iron in the form of Lactoferrin (literaly milkiron) which is one of the anti-microbial agents in milk as well as being the source of iron for the baby.
The outside of the lactoferrin molecule mimics the exterior of a human cell so when a microbe attacks the 'human cell' it bonds permanently with it in the hope of taking it over/using it to reproduce it/whatever that particular microbe does and instead it's bound to a lactoferrin molecule and can be excreted/digested by the baby. This is how a container of bm can have less bacteria in it after a few hours of being expressed than directly after being put in the container.
Breast milk contains 0.5mg per litre and 50% of that is bioavailiable.
Formula contains 10-12mg per litre (on average though different formulas vary) and 4% of that is bioavailable.
Cows milk contains 0.5mg per litre and 0.25mg of that is bioavailable.
The iron that is not absorbed then settles in the stomach and if any bacteria are present within the gut use this excess iron as fuel to reproduce.
These are some of the reasons why babies which have formula are at greater risk for d&v illnesses - they have no human lactoferrin to 'mop' up bacteria/viruses/parasites AND have a source of fuel for bacteria to use to reproduce PLUS if the formula is prepared incorrectly (sub 70C water added to the PIF/used after 2 hours of prep/stored above 4C/etc/etc) then there may be bacteria in the formula already waiting to multiply.
Jung - I did an update on lactoferrin as part of the Colostrum Update back in November. I know you weren't there - did you want me to send a pdf out to you? Plus it was me who instigated the change re benefits -> risks of - I asked why we were doing a whole session on something that didn't exist.....cue very confused group leader and me going
. I thought everyone was on board with the change in language (from a medical/support wiewpoint.