Phytoestrogens are plant hormones that have a chemical resemblance to human estrogen. Chemicals that have similar shapes can sometimes cause similar effects in cells, which has caused concern in some sectors that phytoestrogen-containing foods aren't safe for consumption during pregnancy. As of 2011, there isn't existing scientific evidence to support this claim, however.
Phytoestrogen Safety
In recent decades, many researchers have examined the potential for phytoestrogens to have harmful physiological effects. One hypothesis was that they might increase risk of estrogen-related cancer, while another hypothesis states that they might pose a risk to developing male fetuses. Despite decades of study, however, there's never been any evidence that phytoestrogens pose any harm to humans, whether adult or fetal. Further, they actually appear to have positive health effects, such as decreasing risk of cancer.
Crossing the Placenta
One of the first considerations in determining whether a chemical has the potential to harm a fetus is whether it can cross the placenta. Based upon studies, such as a 2001 study published in "Developmental Brain Research" by Dr. K. Weber and colleagues, phytoestrogens can cross the placenta and show up in a fetus. However, no studies have found any indication of negative health outcomes as a result of phytoestrogen consumption.
Effect on Fetuses
There are no scientific studies that have looked at the effects of phytoestrogen-containing foods on fetuses, simply because it's logistically and ethically challenging to experiment on pregnant women. However, babies who consume soy formula take in more soy--and more phytoestrogens--per pound of body weight than any other group. There have been no studies demonstrating any phytoestrogen-related harm to these babies, from which it is not unreasonable to extrapolate that phytoestrogens are also safe for fetuses.
Other Considerations
During your pregnancy, you can feel free to consume phytoestrogens without worrying that you're harming your developing fetus. In fact, soy--a rich source of phytoestrogens--is a very healthy food for many reasons. It's high in protein, low in fat and is associated with reduced rates of cancer, note Drs. M. Messina and colleagues in a 1991 article in the "Journal of the National Cancer Institute."
References
- "Developmental Brain Research"; Maternal and perinatal brain aromatase: effects of dietary soy phytoestrogens; K. Weber et al; February 2001
- "Journal of the National Cancer Institute"; The role of soy products in reducing risk of cancer; Mark Messina et al; 1991
