Exposure to phytoestrogen genistein before conception can adversely affect female fertility and pregnancy outcomes, depending on the dose and duration of exposure, suggests a new study in mice.
Chronic exposure to genistein has affected pregnancy rates in mice and has been associated with prolonged labor, smaller litters, and higher infant mortality rates, according to a report by University of Illinois. Reproductive Toxicology .
The findings add to a growing body of research that raises troubling questions about the potential health risks of long-term exposure to plant-based estrogen. Genistein is an isoflavone found in soy-based foods and dietary supplements, and, like other plant estrogens, it can be consumed by women to relieve menopausal conditions such as hot flushes, weight gain and depression.
Genistein is among the chemicals that the National Institute of Environmental Health Sciences classifies as endocrine disruptors because they can interfere with bodily systems that are controlled by hormones.
"It's one of the first studies to look at long-term exposure to genistein in adult populations," said Jodi A. Flaws, professor of comparative bioscience at Illinois and a co-author of the article. "Many women take dietary supplements that contain genistein, and there is very little information about its potential reproductive effects in adult women."
In an earlier study, Flaws and colleagues observed that treatment with another phytoestrogen found in licorice inhibited the ability of isolated ovarian follicles to grow and produce sex steroid hormones. William G. Helferich, Professor of Food Science and Human Nutrition, Director of the Botanical Estrogen Research Center at the University, collaborated on this study and this study.
Extending this work, the researchers examined how chronic exposure to genistein affected steroid sex hormone levels and outcomes of pregnancy. Adult female mice in the present study were fed a diet containing 300, 500 or 1000 parts per million of genistein, while their counterparts in the control group consumed foods free of soy and phytoestrogens.
Groups of mice that consumed genistein were exposed for 30, 60, 150, or 240 days, producing serum blood levels equivalent to those of women consuming soy foods or supplements, Shreya Patel said. conducted research as a PhD student at the university.
"When we examined exposed animals for 30 days, the duration of pregnancy - the length of their pregnancy - was reduced, as did premature births," said Flaws. "And after 60 days of exposure, they had fewer pups in their litters."
After 150 days, mice that consumed 500 ppm or 1000 ppm genistein were less likely to become pregnant after mating. According to researchers, only 83% of females from one or the other of these groups were fertile.
After 240 days of treatment, only 50% of the mice in the 300 ppm group were fertile compared to 67% of the mice in the control group. However, genistein appeared to stimulate fertility rates among the two highest dose groups: 83% in the 500 ppm group and 100% in the 1000 ppm group.
"Definitively to say that genistein had a protective effect on fertility, we should have continued the study longer," Patel said. "But it was a very interesting discovery, which correlates with current knowledge and the literature on genistein having a protective effect on some health indicators."
While mice in the 240-day-old treatment group who gave birth carried normal-sized litters, they often killed their offspring, and the puppies were much smaller than their similar-age siblings.
Although the results are preliminary, the researchers said that the potential effects of long-term use of phytoestrogens are poorly known, and women should be cautious about their exposure, especially if they plan to conceive in a close future.
"While women consume these dietary supplements of estrogen, this is an uncontrolled experiment in which safety and effectiveness are unknown," said Helferich.
"With endocrine disruptors, that's the dose that makes the poison," said Patel, who is currently in a postdoctoral program at Northwestern University. "People should be aware of what they consume, and some supplements may not be what they claim to be. It is probably best to consult a doctor or dietician."
Source:
https://news.illinois.edu/blog/view/6367/578337
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