Researchers at North Carolina State University found that bisphenol-A (BPA) exposure in early life stages can actually cause gene expression changes. These effects are seen in a part of the brain called the amygdala, which can lead to increased levels of anxiety. What may surprise you is that soy—which has been accused of mimicking estrogen, as has BPA—prevented the behavioral changes.
BPA and Genetic Changes
Lead author of the study as published in the journal PLOS ONE, Dr. Heather Patisaul is an NC State associate professor of biology. For the research, she and other researchers divided rats into four groups:
- Group I was fed only soy.
- Group II was fed a soy-free diet.
- Group III was fed only soy ad exposed to BPA.
- Group IV was fed a soy-free diet and exposed to BPA.
Rats exposed to BPA were given low doses during gestation, lactation, and throughout puberty. When administered blood tests, the rats dosed with BPA showed levels comparable to those found in humans. The same was true of rats fed a soy diet, which displayed comparable levels of genistein the estrogen-mimicking chemical much abhorred in soy.
Group IV—rats fed no soy and exposed to BPA—showed markedly higher levels of anxiety than the other groups. Their genes had changed, specifically where expressed in the amygdala (a region of the brain that deals with responses to fear and stress, also associated with behavior). The affected genes—estrogen receptor beta and melanocortin receptor 4—both deal with the process of releasing oxytocin, a hormone and neurotransmitter linked to social behavior. Researchers therefore believe that the increased anxiety must have to do with BPA’s ability to change the oxytocin/vasopressin signaling pathway.
The abstract of the study states:
“Early life exposure to Bisphenol A (BPA), a component of polycarbonate plastics and epoxy resins, alters sociosexual behavior in numerous species including humans. The present study focused on the ontogeny of these behavioral effects beginning in adolescence and assessed the underlying molecular changes in the amygdala.”
The Relationship Between Soy and BPA
The rats in Group III—fed a soy-heavy diet and dosed with BPA—showed no increased levels of anxiety. Although both BPA and genistein in soy have both been accused of mimicking estrogen, the two together seemed to subdue the effects. “It is not clear whether these phytoestrogens [found in soy] are what mitigate the effect of BPA, or if it is something else entirely,” says Patisaul. “That’s a question we’re hoping to address in future research.”
BPA is found in a variety of items and foods, including but not limited to:
- Food containers (disposable and reusable)
- Epoxy resins
- Water bottles (and other plastics)
- Canned food
- Paper money
Additionally, BPA (and its close cousin, BPS chemical) has been linked with the following conditions:
- Breast cancer
- Fertility problems
- Feminization of boys
- Accelerated maturation in girls
- Depression and hyperactivity
While the scientists are working on the soy option (which is far from the best option), try these other methods to mitigate the estrogenic effects of BPA.