|
| |
Soy
Infant Formulas |
Soy-based infant formulas are
nutritionally complete, have been proven to promote normal growth and development (Fomon
& Ziegler, 1998), and have been utilized in the United States for over half a century.
They are an excellent alternative and preferred food for children with cow-milk allergy
(Businco et al., 1998). Recently the safety of soy infant formula has been questioned in
regards to its phytoestrogen (genistein and daidzein) content and effects on
neuroendocrine development (Birkbeck, 1998). However, there has been no indication of
chronic adverse effects (including estrogenic effects) or acute toxic effects associated
with modern soy-based formulas (with the exception of allergies and a few rare cases of
effects on thyroid function) (Franke et al., 1998; Klein, 1998). There is also a long
history of use of soyfoods in Asian children (Quak & Tan, 1998) without any increased
incidence of endocrine effects (Klein, 1998).
A recent article found that soy formula provides a much higher level of phytoestrogens
compared to dairy-based infant formulas or human breast milk, in which no phytoestrogens
were detected (Irvine et al., 1998). A paper by Setchell (1997) showed that 4 month old
infants fed soy milk formula have plasma isoflavone levels significantly greater than
infants fed human breast milk or cow-milk formula. The study measured not only the
biologically active free genistein and daidzein in plasma, but a total of both free and
conjugated isoflavones. However, writing about the safety of soy infant formula in another
article, Setchell & Cassidy (1999) wrote that "despite the use of these feedings
for more than 30 years, there is no obvious evidence to support negative effects from
exposure to phytoestrogens". An article by Huggett (1997) suggests that plasma
concentrations of total genistein and daidzein do not provide adequate information to
predict a biological outcome and his data shows that soy isoflavones are metabolized by
infants into bound (relatively inactive) conjugates which are more rapidly excreted. None
of the plasma samples that were examined from infants aged 2-5.5 months (whose only source
of food was soy-based infant formula) contained detectable levels of free
isoflavones.
A study presented at the Second International Symposium on the Role of Soy in Preventing
and Treating Chronic Disease held in Belgium,1996 found isoflavones in urine from soy-fed
infants but not dairy-fed infants and that infants as young as 4 weeks can digest, absorb
and excrete genistein and daidzein as efficiently as adults (Irvine et al., 1998).
However, even though data shows that infants absorb isoflavones, no adverse biologic or
clinical effects of the isoflavones on the infant have been shown (Klein, 1997). At the
Experimental Biology Meeting in Washington, 1999, one animal study designed to see the
reproductive and growth effects of the form of protein used in most soy-based infant
formulas found that while the soy diet led to lower growth rates during puberty, there
were no signs of reduced fertility, estrogenic responses or endocrine problems (Badger et
al., 1999).
Only an extensive retrospective analysis could determine whether exposure of infants to
soy isoflavones is without question not harmful in some way to certain individuals, but
the lack of reported adverse effects on the millions of infants consuming soy formulas
containing isoflavones, suggests there are no biologic or clinical consequences (Klein,
1997). |
*These statements
and products have not been evaluated by the food and drug admininistration. Products are
not
intended to diagnose, treat, cure or prevent any disease. As with any products or
diet, please consult your physician first. |
|
