New research shows that a soy-rich diet may help reduce anxiety in rats
after exposure to the chemical bisphenol A.
New research led by researchers
at North Carolina State University shows that a soy-rich diet may help reduce
anxiety after exposure to the chemical bisphenol A (BPA) early in life.
“We knew that BPA could cause
anxiety in a variety of species, and wanted to begin to understand why and how
that happens,” said lead author Dr. Heather Patisaul, an associate professor of
biology at NC State.
BPA is a chemical used in a wide
variety of polycarbonate plastics and epoxy resins, and is used in consumer
products such as some food containers.
In the study, rats were exposed
to low doses of BPA during gestation, lactation (nursing), and through puberty.
One group of animals was fed only soy; one group was fed a soy-free diet; one
group was fed only soy and exposed to BPA; and one group was fed no soy and
exposed to BPA.
Blood tests showed that the
animals exposed to BPA had BPA levels well within the range found in humans.
Similarly, blood tests of animals fed soy showed levels of genistein, an
estrogen-like chemical found in soy, were at levels within the human range for
vegetarians and others who regularly consume soy foods.
Among adolescent rats on the
soy-free diet, both males and females that had been exposed to BPA exhibited
significantly higher levels of anxiety. The researchers also found, for the
first time, associated gene changes in the amygdala, a brain region known to
play a role in mediating responses to fear and stress.
Two of the affected genes were
estrogen receptor beta and the melanocortin receptor 4. Both are required for
oxytocin release, thus changes in oxytocin/vasopressin signaling pathways may
underpin the behavioral changes. Oxytocin is a hormone and neurotransmitter that
has been linked to social behavior.
The researchers found that
adolescent rats on the soy-rich diet did not exhibit anxiety – suggesting that
the soy-rich diet may mitigate the effects of BPA.
“Soy contains phytoestrogens that
can also affect the endocrine system, which regulates hormones,” Patisaul said,
expressing caution on the adoption of a soy-rich diet.
“It is not clear whether these
phytoestrogens are what mitigate the effect of BPA, or if it is something else
entirely. That’s a question we’re hoping to address in future research.”
The article can be found at: Patisaul HB et al. (2012)
Anxiogenic effects of developmental Bisphenol A exposure 1 are associated with
gene expression changes in the juvenile rat amygdala and mitigated by soy.
Source: NCSU
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