Phytoestrogen in soy impedes egg, embryo growth, finds mouse study.

Environmental Health News

Women who are having difficulty conceiving may want to cut back on their soy consumption after a mouse study reveals that dietary exposure to genistein, a compound found in soy foods, can reduce the odds of a successful pregnancy in multiple ways. The study examined the impact of genistein exposure on oocytes, or eggs, from adult mice and found it can impair oocyte maturation, reduce their potential to become fertilized and hamper the growth of the newly formed embryo. The results reveal how natural compounds like genistein may have both risks – it can act as an endocrine disruptor to affect female reproduction – and benefits – such as protecting the heart.

What did they do?

For one set of experiments, mice were exposed to genistein for 4 days through their drinking water. Their oocytes were then collected and cultured in petri dishes.  For the remaining experiments, the oocyctes were collected from animals that did not eat genistein and then exposed to 1, 5 or 10 micromoles (µM) of genistein in the petri dishes.  In both cases, the oocyte collection and culturing procedure was similar to how in vitro fertilization is done in humans.

Blood levels in people eating soy-rich diets are generally in the range of 1-5 µM, so the exposure levels used in this study are similar to what a human fetus could be exposed to.

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Author: Leslie Carol Botha

Author, publisher, radio talk show host and internationally recognized expert on women's hormone cycles. Social/political activist on Gardasil the HPV vaccine for adolescent girls. Co-author of "Understanding Your Mood, Mind and Hormone Cycle." Honorary advisory board member for the Foundation for the Study of Cycles and member of the Society for Menstrual Cycle Research.