A new study shows that soy can help offset the harmful effects of BPA on fertility—this is despite articles online saying soy can get in the way of getting pregnant.
Many websites claim to tell you what foods to eat to help you get pregnant (and which to avoid), but much of that advice is not backed by scientific evidence. But if you can believe anyone, it should be Harvard scientists—and they've discovered one food linked to improved pregnancy rates: soy.
Soy's beneficial effects on fertility
The study, published in the Endocrine Society's Journal of Clinical Endocrinology & Metabolism, explored the relationship between soy and Bisphenol A (BPA), a harmful chemical found in plastics including water bottles and food containers, as well as in can linings. Based on previous tests that showed the adverse effects of BPA on rodents' fertility were reduced when the mice ate soy, the researchers wanted to see if the same was true in humans. So, they looked at data from 239 women undergoing IVF to compare pregnancy rates, levels of BPA in their urine and how much soy they ate. "We found that among women who were undergoing infertility treatment with assisted reproductive technologies [IVF], urinary bisphenol A levels were related to a lower chance of having a live birth—nearly 50 percent lower chances—among women who did not consume soy foods," first author Jorge E. Chavarro, M.D., Sc.D, an associate professor at the Harvard T.H. Chan School of Public Health, tells Fit Pregnancy. "But [BPA] had no impact on live births among women who did consume soy."
Based on these findings, it appears that soy reduces the negative effects of BPA, but how are they connected? BPA has been shown to have a negative impact on fertility by disrupting the endocrine system, and has estrogen-like properties that can mess with your hormones. Although the exact mechanism isn't clear, soy somehow seems to block BPA's influence on the body. In the rodent studies, "the investigators showed that soy was able to offset the effects on BPA," Dr. Chavarro says. "BPA was able to switch on and off certain genes, and soy prevented BPA from doing so."
Ironically, soy also has estrogen-like properties, so women looking to get pregnant or who are having trouble conceiving are sometimes told to avoid it—although Dr. Chavarro says that advice is misguided. "There is a large amount of lay literature, particularly on the web, suggesting that soy consumption may harm fertility," he says. But, "most of the scientific evidence, including evidence from randomized clinical trials, suggests exactly the opposite for women. Both BPA and soy have estrogenic activities. This does not mean, however, that they raise estrogens nor that their estrogenic activity is the only biological effect they can have."
TTC? Consider eating more soy
Should you increase your soy intake if you're trying to get pregnant? Dr. Chavarro says yes, especially if you're undergoing fertility treatments. "There have been several studies over the last few years showing that pre-conceptional soy consumption or use of soy supplements increases live births among women undergoing infertility treatment," he says. How much you need to take to see a benefit is unclear, he says, but "in our study, women benefiting from soy consumption ate the equivalent of one serving of soy foods—tofu, soy-based veggie burgers, tempeh—every two to three days." Before undergoing a major diet change, though, talk to your doctor.
Related Recipe: Tofu and Spinach with Garlic Sauce
In addition, if you're trying to conceive you can attempt to reduce your exposure to BPA—although that's not as easy as it sounds. "Exposure to BPA is extremely pervasive," Chavarro says. "Based on nationally representative surveys we know that more than 90 percent of Americans are exposed at varying levels." But there are some steps you can take, like "switching from consuming canned foods to their fresh or frozen counterparts, replacing hard polycarbonate plastic food containers with glass or metal containers, and not handling thermal receipts such as those used in supermarkets, ATMs and gas stations," Dr. Chavarro says.
This study is groundbreaking because it's the first to show a link between diet and BPA in humans, although it still doesn't prove cause and effect. "Even though we did our best to rule out and account for other factors that could explain this interaction, such as other characteristics of women's diet or of their medical and reproductive history, there is still a chance that some other unmeasured factor could be responsible for the interaction we identified," Dr. Chavarro says. More research is needed, but the study does give hope for how we may be able to reverse the harmful effects of outside toxins. "Our results highlight the possibility that diet and other modifiable lifestyle factors could impact how BPA, and possibly other environmental chemicals, impact health in humans," Dr. Chavarro says.