Genistein Affects Sexual Differention in Developing Embryos

This finding was published in the April 2003 issue of the Journal of Urology.

Genistein, an isoflavone derivative related to coumarin, is found in soy products and has been touted as a natural cancer preventative. There are a number of isoflavones in soy products, but research has shown that genistein is the most potent inhibitor of the growth and spread of cancerous cells.

In addition to its anticancer activity, genistein effects differentiation of the male reproductive organs. To determine if perinatal genistein exposure at doses common in human diets altered masculinization, investigators at Johns Hopkins University (Baltimore, MD, USA; www.jhu.edu) examined the development of the external genitalia, testes, wolffian ducts, and sexual behavior in male rats whose mothers were fed genistein-supplemented diets during early development.

They found that these rats 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.

"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,” explained senior author, Dr. Amy B. Wisniewski, a researcher at the Johns Hopkins University's Children's Center.

While these findings did not indicate that genistein has a similar effect in humans, the authors suggest that the increasing popularity of soy and soy-based foods, such as tofu and some infant formulas, warranted further research to determine if genistein exposure in the womb and during breast-feeding influences human reproductive development.