CHEMICAL
IN SOY ALTERS REPRODUCTIVE ORGANS
Researchers at the Johns Hopkins Children's Center and the Johns
Hopkins Bloomberg School of Public Health report that male rats
whose mothers were fed diets containing genistein, a chemical found
in soybeans, developed abnormal reproductive organs and experienced
sexual dysfunction as adults.
While these findings do not indicate that genistein has a similar
effect in humans, researchers say the increasing popularity of
soy and soy-based foods, such as tofu and some infant formulas,
may warrant further research to determine if genistein exposure
in the womb and during breast-feeding influences human reproductive
development.
In the study, described in the April issue of the Journal of Urology,
pregnant female rats were randomly assigned to one of three regimens:
a genistein-free diet, a diet supplemented with a low dose of genistein,
and a diet with a high dose of genistein.
Male offspring were exposed to genistein indirectly through maternal
consumption during pregnancy and lactation.
When the genistein-exposed offspring matured, researchers found
the males had smaller testes and a larger prostate gland compared
to unexposed rats. Although their sperm counts were normal, exposed
adult males had lower testosterone levels and were also less likely
to ejaculate when presented with the opportunity to mate with a
female.
"The effects of genistein continued long after the rats were
exposed, leading us to believe that exposure to this plant-derived
estrogen during reproductive development can have long-term detrimental
effects in males," said the study's lead author, Amy B. Wisniewski,
Ph.D., a researcher at the Johns Hopkins Children's Center.
"Genistein may act as an estrogen or an anti-androgen, blocking
the function of endogenous androgens - the sex hormones necessary
for males to develop a normal reproductive system - and ultimately
leading to the reproductive abnormalities and sexual dysfunction
we saw in the exposed rats," added study co-author Sabra L.
Klein, Ph.D., of the School of Public Health. "However, additional
research is needed to determine if this is the case."
Whether the long-term effects of genistein on the reproductive
development of male rats are caused by exposure during gestation,
lactation, or both also requires further investigation, Wisniewski
said.
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