The male offspring of rats fed diets containing genistein, a chemical found in soybeans, developed abnormal reproductive organs and had sexual dysfunction as adults.

This finding may indicate a need for further research to determine whether exposure to genistein while in the womb and during breastfeeding influences human reproductive development, according to researchers.

The study involved pregnant rats that were fed one of three diets: a genistein-free diet, a diet supplemented with a low dose of genistein, and a diet with a high dose of genistein. The male offspring were, therefore, exposed to genistein indirectly through their mothers’ diets during pregnancy and lactation.

Researchers found that while the sperm counts of genistein-exposed males were normal, they had smaller testes and a larger prostate gland than unexposed rats. They also had lower testosterone levels and were less likely to ejaculate than unexposed rats.

The effects of genistein exposure continued long after the rats were exposed, leading researchers to say that exposure during reproductive development may have negative, long-term consequences in males.

It is thought that genistein may act as an estrogen or an anti-androgen, blocking the function of the sex hormones, known as endogenous androgens, necessary for males to develop a normal reproductive system.

Further studies are needed to determine whether exposure to genistein during gestation, lactation, or both caused the long-term effects seen in the study, researchers noted.

Journal Urology April 2003;169(4):1582-1586

Dr. Mercola's Comments:

If you are new to this newsletter you might be surprised to learn that soy is not the health food that it is made out to be. I regularly see women who have had thyroid problems as a result of consuming soy products regularly. If you need more information and are startled by this comment I encourage you to review the details in the link below. You will learn that unfermented soy has many negative inhibitors of digestion and potent hormones that typically will not push your body in the direction of health. Further, soy formula is one of the absolute worst foods you can give to your child, as it will expose them to very high levels of hormones that can have negative influences as they grow older. Please recognize that fermented soy products are typically not associated with many of these problems and actually are reasonable to include in your diet. Fermented soy products include miso, natto and tempeh. Related Articles: Why Soy Can Damage Your Health