Soy products—foods that contain soybeans and their derivatives—are fairly commonplace and are often used as meat substitutes. Though there is some debate about how healthy soy products are, new research suggests that soy may protect women from the harmful effects of a chemical commonly found in food.
According to a press release issued by the Endocrine Society, a new study found that eating soy regularly could improve success rates of infertility treatments among women who are exposed to bisphenol A (BPA).
BPA is a chemical found in many food containers, including polycarbonate plastic water bottles and can linings. BPA can mimic estrogen, one of the two main sex hormones in women. According to the press release, the Centers for Disease Control and Prevention (CDC) estimates that more than 96 percent of Americans have BPA in their bodies.
This is significant, given the fact that as of 2014, nearly 100 epidemiological studies had been published linking BPA to health problems, including reproductive disorders, according to the Society and the International Persistent Organic Pollutant Elimination Network's Introductory Guide to Endocrine-disrupting Chemicals. Despite these findings, the U.S. Food and Drug Administration (FDA) supports the safety of BPA approved for use in food containers and packaging, and says that studies performed by the FDA’s National Center for Toxicological Research (NCTR) have shown no effects of BPA from low risk exposure.
"Our study is the first to show a possible interaction between soy and BPA in humans," first author Jorge E. Chavarro, MD, ScD said in the press release. Chavarro is from the Harvard T.H. Chan School of Public Health, Brigham and Women's Hospital and Harvard Medical School in Boston, MA.
"This is consistent with research in mice that found a soy-rich diet could protect against reproductive health problems associated with BPA exposure. More research is needed to determine why soy has this effect in humans," Chavarro said in the press release.
According to the study, researchers analyzed 239 women who underwent at least one in vitro fertilization (IVF) cycle at the Massachusetts General Hospital Fertility Center between 2007 and 2012, examining the relationship between their BPA exposure, diet and success rates with IVF. The women were between 18 and 45 years old.
Researchers analyzed the women’s urine samples to measure BPA exposure and administered a lifestyle questionnaire that assessed how frequently they ate soy-based foods. Of the 239 women, 176 ate soy products.
The study found that the women who had high levels of BPA, but did not eat soy food, had lower rates of embryo implantation, fewer pregnancies that progressed to the point where the fetus was visible on an ultrasound and fewer live births than women who had lower levels of BPA in their bodies. Conversely, BPA had no impact on IVF outcomes in the women who frequently ate soy.
"Although it is recommended that women trying to get pregnant reduce their exposure to BPA, our findings suggest that diet may modify some of the risks of exposure to BPA, a chemical that is nearly impossible to completely avoid due to its widespread use," senior author Russ Hauser, MD, ScD, MPH, said in the press release. Hauser hails from the Harvard T.H. Chan School of Public Health, Massachusetts General Hospital and Harvard Medical School in Boston, MA.
The authors conclude that researchers should design studies that assess both diet and environmental exposures to truly appreciate the risks to human health.
The full study was published in the Endocrine Society's Journal of Clinical Endocrinology & Metabolism on January 27. It was funded by the National Institutes of Health. The authors disclosed no conflicts of interest.