An animal study has raised concerns about the safety of eating soy during pregnancy after male offspring of rats fed a chemical found in soy suffered sexual development problems.
Male rats exposed to the natural chemical in soy, called genistein, while still in the womb and later through breastfeeding developed large prostate glands and small testes and were unable to mate.
Although the finding does not prove genistein is harmful to humans, scientists at Johns Hopkins Bloomberg School of Public Health in Maryland who conducted the research are calling for more studies.
Genistein is a phytoestrogen--a plant chemical that can mimic the effect of the female hormone estrogen. It is found in some baby formulas and supplements used by women to relieve the symptoms of the menopause.
Synthetic estrogen-like chemicals in plastics and birth control pills have been blamed for changing the gender of fish in heavily polluted streams.
Researchers at Johns Hopkins fed pregnant rats genistein-laced diets equivalent to what people in Asia and the west might eat they found it had severe effects on the male offspring. In addition to the large prostate and small testes, the male rats also had a slightly enlarged thymus gland, which produces immune cells. Sons of women who have eaten soy during pregnancy have not shown similar effects but some doctors are taking a cautious approach.
The urologists on this project are actually advising pregnant women to avoid soy, say the researchers. In the animal study, moderate levels of genistein had a bigger effect on the rats than a very large dose of the chemical.
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