Jacqui,
Yikes!! This makes my hair stand on end! There are SO many reasons
this is a bad idea. Soy milks contain phytates which interfere with
calcium, magnesium, iron, and zinc absorbtion. It could be quite
dangerous and harmful to her baby to reduce his levels of these
minerals. This could actually cause malnutrition. Soy milks also
contain phytoestrogens which affect hormone levels in humans. While
she may consider this to be beneficial for herself, she must consider
that her baby is a first of all a male, and secondly he is at an age
of when messing with his hormones may have long-lasting unintended
effects. One researcher found that exclusively soy formula-fed
babies receive the equivalent of 1-2 birth control pills worth of
hormones per day. Note that 16 oz of soy milk per day for one month
has been shown to affect the menstrual cycles of grown women -- think
how much that same 16 oz of soy milk might affect a tiny baby whose
body is very small compared to a grownup.
It is also important to note that while soy has a long history of use
in Asian countries, soy products and soy milk in particular were not
traditionally fed to infants.
Soy isoflavones are known to interfere with thyroid function --
again, this is likely to be harmful to a baby who is undergoing rapid
development.
Here are some refs to share with her.
<http://humrep.oupjournals.org/cgi/content/full/17/7/1692> Richard
M. Sharpe,1, Bronwen Martin, Keith Morris, Irene Greig, Chris
McKinnell, Alan S. McNeilly and Marion Walker. Infant feeding with
soy formula milk: effects on the testis and on blood testosterone
levels in marmoset monkeys during the period of neonatal testicular
activity. Human Reproduction, Vol. 17, No. 7, 1692-1703, July 2002.
This study showed that baby monkeys fed soy formula had significantly
suppressed testosterone levels, compared to their cow's milk
formula-fed twin brothers.
Male human babies normally have a "prolonged 'neonatal testosterone
rise' when testosterone levels increase to low adult levels during
the first 4-6 months of life, associated with activation of
gonadotrophin secretion, Sertoli cell proliferation, and a steep rise
in the secretion of inhibin B by the latter cells. . . . The role
of the neonatal testosterone rise in the human male remains unclear,
though effects on the immune system, on sexually dimorphic brain
development, the testis and reproductive tract, and genitalia are
distinct possibilities, based on studies in non-human primates which
also exhibit a neonatal testosterone rise."
"It seems likely that there are other roles for the neonatal
testosterone rise, for example on development of the reproductive
tract and prostate."
"For human male infants fed with SFM [soy-based infant formula]
within the first 3-4 months, significant attenuation of the neonatal
testosterone rise is likely to occur, based on the present findings.
Penile growth in the human male is reported to occur at a higher rate
during the neonatal period than at any other phase of life, as is the
case in the rhesus monkey. Disorders of androgen production or action
are associated with under-development of the penis in the human male."
" . . .the most cautious interpretation of our findings is that
feeding human infant males with SFM in the first 3-5 months of life
will exert effects on the neonatal testosterone rise and consequently
on tissues/processes that are affected or regulated by this increase.
Until we know what these tissues/processes are, it would seem prudent
to avoid feeding infants with SFM whenever alternatives are possible."
<http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=9217716>
Setchell KD, Zimmer-Nechemias L, Cai J, Heubi JE. Exposure of
infants to phyto-oestrogens from soy-based infant formula. Lancet.
1997 Jul 5;350(9070):23-7.
" . . a 4-month-old infant fed soy formula would be exposed to 28-47
mg per day, or about 4.5-8.0 mg/kg bodyweight per day, of total
isoflavones. Mean (SD) plasma concentrations of genistein and
daidzein in the seven infants fed soy-based formulas were 684 (443)
ng/mL and 295 (60) ng/mL, respectively, which was significantly
greater (p < 0.05) than in the infants fed either cow-milk formulas
(3.2 [0.7] and 2.1 [0.3] ng/mL), or human breast-milk (2.8 [0.7] and
1.4 [0.1] ng/mL), and **an order of magnitude higher per bodyweight
than typical plasma concentrations of adults consuming soy foods.**
INTERPRETATION: **The daily exposure of infants to isoflavones in soy
infant-formulas is 6-11 fold higher on a bodyweight basis than the
dose that has hormonal effects in adults consuming soy foods**.
Circulating concentrations of isoflavones in the seven infants fed
soy-based formula were 13000-22000 times higher than plasma
oestradiol concentrations in early life, and may be sufficient to
exert biological effects, whereas the contribution of isoflavones
from breast-milk and cow-milk is negligible." (emphasis mine)
A couple of other sources for soy information are
http://www.mercola.com/article/soy/ (especially the article about
historical use of soy) and http://www.soyonlineservice.co.nz/ .
These both clearly have the opinion that unfermented soy (ie most soy
products available today) are not good for us.
Good luck with this Jacqui! A mom who would feed straight soymilk to
a 3 week old, I shudder to think what else she might believe.
Warmly,
Margaret
Longmont, CO
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