Lars Hanson's book _The Immunobiology of Human Milk: How 
Breastfeeding Protects Babies_ is absolutely jam-packed with 
references, hundreds of them.

A couple of points just from flipping through the book:
In the chapter The Development of Host Defense in the Fetus and Baby, 
it explains that the IgG response is not developed until about 2 
years of age.  IgG is a primary defense against the polysaccharide 
capsules of several important pathogens including pneumococci, 
meningococci, Hib, and certain e. coli.  Hanson cites research 
showing that vaccines against these pathogens became reliable when 
the polysaccharide was linked to a protein carrier such as diphtheria 
or tetanus toxoid.  Babies apparently could respond to the protein 
part and that apparently helped them also respond to the 
polysaccharide part.  (Or something like that -- this isn't my 
specialty!)  (Robbins JB et al, JAMA 1996; Wuorimaa et al, J Infect 
Dis 2001)  Meanwhile, until the child is making all the IgG it needs, 
other factors in breastmilk target these pathogens and/or make the 
child's system unhospitable to them.

The next chapter, Mother's Defense of the Offspring Via Milk, makes 
me think that the whole discussion about when exactly the infant's 
immune system matures is a red herring.  The fact is that breastmilk 
promotes the health and development of the baby in so many ways 
beyond providing this or that immunoglobulin.  For example, SIgA in 
breastmilk promotes the growth of low-virulence bacteria in the 
baby's gut, and restricts the growth of dangerous/virulent strains. 
During its passage through the baby's GI tract, SIgA binds microbes 
and prevents them from attaching to the mucosal membranes -- the 
first step in infection.  Breastfed babies/children *of any age* 
continue to enjoy this protection against infection from the mother's 
SIgA.

One of Hanson's take-home points is that breastmilk protects 
babies/children in ways that allow the child to reserve his/her 
energy for growth and development.  SIgA in particular takes out 
pathogens without their triggering an energy-consuming inflammatory 
defense on the part of the child.  This is a benefit to the child.

Another thing that bolsters the argument for continued bfdg is thymus 
size.  Breastfed babies have much larger thymus glands (2 times 
larger) than non-breastfed babies, and the effect is greater the 
longer the duration of bfdg: 
<http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=10592070&query_hl=1&itool=pubmed_docsum> 
"At 10 months the thymic index was significantly higher in those 
still being breast-fed compared to infants who had stopped 
breast-feeding between 8 and 10 months of age (P=0.05). This 
difference became more significant when controlled for the influence 
of infectious diseases (P=0.03). In infants still breast-fed at 10 
months there was a significant correlation between the number of 
breast-feeds per day and their thymic index (P=0.01).Conclusion The 
effect of breast-feeding on thymus size is likely to be caused by 
immune modulating factors in breast milk. Breast milk influences 
thymic size in late infancy."

I think the doctor's comment needs to be reframed.  Of course babies 
can survive without breastfeeding after 2 months -- or without ever 
breastfeeding at all, for that matter.  The question should be, what 
does breastfeeding do for babies at 2 months, 6 months, or whatever 
age?  At any point, the answer is "Lots!"  Yes, the need of the baby 
for mother's milk is more urgent in the early months.  But the 
importance of bfdg doesn't just vanish at some arbitrary age.

I think I am in danger of soapboxing so I will stop here.  I highly 
recommend the Hanson book (if only docs like the one you mentioned 
would read it!!).  It is very dry reading but it is a goldmine of 
references.

Warmly,
Margaret
mom of 3, LLLL
Longmont, CO

>I just had a colleague who also happens to be an MD say out loud in 
>front of several nurses that breastfeeding only makes a difference 
>for the first 2 months of life, after that the newborn has a mature 
>immune system and that after 2 months it makes no difference whether 
>you formula feed or breastfeed or not.....
>   ok,

             ***********************************************

To temporarily stop your subscription: set lactnet nomail
To start it again: set lactnet mail (or digest)
To unsubscribe: unsubscribe lactnet
All commands go to [log in to unmask]

The LACTNET email list is powered by LISTSERV (R).
There is only one LISTSERV. To learn more, visit:
http://www.lsoft.com/LISTSERV-powered.html