Study in mice finds dietary levels of genistein may adversely affect female fertility

November 14, 2017, University of Illinois at Urbana-Champaign
A new study of mice by scientists at the University of Illinois raises concerns about the potential impact that long-term exposure to genistein prior to conception may have on fertility and pregnancy. The study was conducted by, from left, food science and human nutrition professor William G. Helferich, comparative biosciences professor Jodi A. Flaws and animal sciences research specialist James A. Hartman. Credit: L. Brian Stauffer

Exposure to the phytoestrogen genistein prior to conception may adversely affect female fertility and pregnancy outcomes, depending on the dosage and duration of exposure, a new study in mice suggests.

Chronic preconception to genistein affected pregnancy rates in mice and was associated with prolonged labor, smaller litters and pups, and higher rates of pup mortality, scientists at the University of Illinois report in a paper accepted for publication in the journal Reproductive Toxicology.

The findings add to a growing body of research that raises troubling questions about the of long-term exposure to plant-based estrogens. Genistein is an isoflavone found in soy foods and dietary supplements, and, like other plant estrogens, may be consumed by women to relieve menopausal conditions such as hot flashes, weight gain and depression.

Genistein is among the chemicals that the National Institute of Environmental Health Sciences classifies as because they can interfere with bodily systems that are controlled by hormones.

"This is one of the first studies to look at long-term exposure to genistein in adult populations," said Jodi A. Flaws, a professor of comparative biosciences at Illinois and a co-author of the paper. "Many women are taking that contain genistein, and there is very little information on its potential effects on reproduction in adult women."

In a prior study, Flaws and her colleagues observed that treatment with another phytoestrogen found in licorice inhibited the ability of isolated ovarian follicles to grow and make . Food science and human nutrition professor William G. Helferich, the director of the Botanical Estrogen Research Center at the university, collaborated on that and the current study.

Extending that work, the researchers examined how chronic genistein exposure affected sex steroid hormone levels and . Adult female mice in the current study were fed a diet containing 300, 500 or 1,000 parts per million of genistein, while their counterparts in the control group consumed food that was soy- and phytoestrogen-free.

The groups of mice that consumed the genistein were exposed to it for 30, 60, 150 or 240 days, which produced blood serum concentrations equivalent to those found in women who consume soy foods or supplements, said Illinois alumna Shreya Patel, who conducted the research as a doctoral student at the university.

"When we looked at animals exposed for 30 days, the gestation time - the length of time they were pregnant - was decreased, similar to premature births," Flaws said. "And after 60 days' exposure, they had fewer pups in their litters."

After 150 days, the mice that consumed 500 ppm or 1000 ppm of genistein were less likely to become pregnant after mating. Only 83 percent of the females in either of those groups were fertile, the researchers found.

After 240 treatment days, only 50 percent of mice in the 300-ppm group were fertile compared with 67 percent of those in the control group. However, genistein appeared to boost fertility rates among the two highest dose groups: 83 percent in the 500-ppm group and 100 percent in the 1,000-ppm group conceived.

"In order to say definitively that genistein was having a protective effect on fertility we would have had to continue the study longer," Patel said. "But that was a very interesting finding, which correlates with current knowledge and literature about having a protective effect on certain health indicators."

While mice in the 240-day treatment group that gave birth bore normal-sized litters, they often killed their pups, and the pups were much smaller than peers of similar age.

Although the findings are preliminary, the researchers said that little is known about the potential effects of long-term phytoestrogen use, and women should be cautious about their exposure, especially if they plan to conceive in the near future.

"While women are consuming these dietary estrogenic supplements, this is an uncontrolled experiment in which the safety and efficacy are unknown," Helferich said.

"With endocrine disruptors, it's the dose that makes the poison," said Patel, who currently is in a postdoctoral program at Northwestern University. "People should be aware of what they're consuming, and some supplements may not be what they claim to be. It's probably best to consult a doctor or a dietitian."

Explore further: Soy isoflavones may accelerate progression of breast cancer

More information: Shreya Patel et al, Preconception exposure to dietary levels of genistein affects female reproductive outcomes, Reproductive Toxicology (2017). DOI: 10.1016/j.reprotox.2017.09.014

Related Stories

Soy isoflavones may accelerate progression of breast cancer

February 25, 2014
Women with estrogen-responsive breast cancer who consume soy protein supplements containing isoflavones to alleviate the side effects of menopause may be accelerating progression of their cancer, changing it from a treatable ...

Understanding when eating soy might help or harm in breast cancer treatment

February 1, 2017
Georgetown Lombardi Comprehensive Cancer Center researchers have used animal models to reveal new information about the impact - positive and negative - that soy consumption could have on a common breast cancer treatment.

Gene mapping reveals soy's dynamic, differing roles in breast cancer

April 28, 2015
Scientists have mapped the human genes triggered by the phytonutrients in soy, revealing the complex role the legume plays in both preventing and advancing breast cancer.

Animal study shows why long-time consumption of soyfoods reduces breast cancer recurrence

April 20, 2015
Women diagnosed with breast cancer are often told not to eat soyfoods or soy-based supplements because they can interfere with anti-estrogen treatment. But new research being presented at the American Association for Cancer ...

Recommended for you

New study reveals time and day women are most likely to give birth

June 15, 2018
A new study has found that the time and day that women give birth can vary significantly depending on how labour starts and the mode of giving birth.

Study unmasks scale of patient doctor divide

June 13, 2018
A study has estimated that around three million Britons—or 7.6 % of the country—believe they have experienced a harmful or potentially harmful but preventable problem in primary healthcare.

Lentils significantly reduce blood glucose levels, study reveals

June 13, 2018
Replacing potatoes or rice with pulses can lower your blood glucose levels by more than 20 per cent, according to a first-ever University of Guelph study.

Researcher studies the impact religion has on sleep quality

June 13, 2018
Can a person's religious practices impact their sleep quality? That's the focus of a new study by Christopher Ellison in The University of Texas at San Antonio (UTSA) Department of Sociology and his collaborators.

Mediterranean-style eating with lean, unprocessed red meat improves heart disease risk

June 13, 2018
Adopting a Mediterranean-style eating pattern improves heart health, with or without reducing red meat intake, if the red meat consumed is lean and unprocessed, according to a Purdue University nutrition study.

Sleeping too much or not enough may have bad effects on health

June 12, 2018
Fewer than six and more than ten hours of sleep per day are associated with metabolic syndrome and its individual components, according to a study published in the open access journal BMC Public Health that involved 133,608 ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.