http://www.eurekalert.org/pub_releases/2003-03/jhmi-cis031003.php
Chemical in soy alters reproductive organs in male rats
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.
The abstract:
http://www.jurology.com/article.asp?ISSN=0022-5347&VOL=169&ISS=4&PAGE=1582
