Mother's intake of soy may affect development of fetus
Mother's intake of soy may affect development of fetus
NEW YORK, Nov 04 (Reuters Health) -- A high intake of phytoestrogens
-- substances found in soybeans and other legumes -- during pregnancy
may affect the developing fetus, and the timing of puberty later in the
child's life, according to scientists at the Cedars-Sinai Medical
Center.
However, much more research will need to be done before it is known
whether or not pregnant women should limit their soy intake, the
researchers note.
Phytoestrogens, or isoflavones, mimic the role the sex hormone
estrogen plays in the body. Some studies have suggested that
phytoestrogens may help to treat the symptoms of menopause. But in the
fetus, these substances may affect how tissues develop.
In a press release, Dr. Claude Hughes of the Cedars-Sinai Medical
Center in Los Angeles, California, explained that "in the first months
of life, there is good reason to believe... that sex hormones are very
important in getting things organized properly.'' He added that "if mom
is eating something... that can act like sex hormones, it is logical to
wonder if that could change the baby's development.'' Hughes and his
colleagues presented their results at the Third International Symposium
on the Role of Soy in Preventing and Treating Chronic Disease, held in
Washington, DC.
The researchers fed pregnant rats either corn oil (as a 'control')
or genistein -- a component of soybeans known to mimic estrogen in the
body. Both sexes of newborn rats whose mother consumed genistein had
lower weights at birth than the newborns of rats fed corn oil. The
investigators also observed a masculinizing effect in these newborns
and early onset of puberty in the males.
"Whatever the clocks are in the brain that control the timing of
puberty appear to have been advanced by a couple of days, which is
highly significant in this kind of animal model,'' Hughes explained.
Hughes and his team then measured levels of phytoestrogens and a
compound found in pesticide that inhibits testosterone formation in
amniotic fluid (fluid around the fetus in the womb) of human mothers
between 16 and 20 weeks of pregnancy. The researchers found that 30% of
the human fetuses received exposure to significant levels of the
pesticide compound and 40% were exposed to phytoestrogens at a level up
to 180 times that of estrogen produced by the mother.
"The human fetus is exposed to physiologically relevant levels of
(these substances) during this critical period of... development,''
Hughes and colleagues write. They note that "the effect of these
exposures, if any, is unknown at this time.''
However, in the press release, Hughes commented that he believes
that the effects observed in the rats "`will be at least somewhat
predictive of what occurs in humans. There is no reason to assume that
there will be gross malformations of fetuses but there may be subtle
changes, such as neurobehavioral attributes, immune function, and sex
hormone levels.''
In an interview with Reuters Health, Hughes commented that these
results cannot be used to make recommendations about consuming soy
products during pregnancy. "Do these compounds (phytoestrogens and
pesticide compound) individually affect the fetus? We don't know. Do
they interact in some way? We don't know.''
Hughes added that these results "could be nothing or could be
something of great concern". His group will attempt to determine the
effects of fetus exposure to phytoestrogens in future studies, he said.
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