Consumption of Foods with High Soy Content is Associated with Lower Sperm Concentrations in Men

Russ Hauser, MD, Ph.D.
Department of Environmental Health, Harvard School of Public Health
NIEHS Grants R01ES009718 and P30ES000002

New research from the Harvard School of Public Health reports that men who eat a high amount of soy-based food products have lower total sperm counts. Soy is rich in estrogenic compounds known as isoflavones including genistein, daidzein, and glyciten.

The medical literature is replete with reports of steep drops in sperm count over the last 60 years in the U.S. and Europe. Possible explanations implicate increased exposure to endocrine disruptors and natural and synthetic estrogens.

In the current study, the 99 research subjects were the male partners of couples being evaluated at the Massachusetts General Hospital Fertility Center. They were asked to complete a questionnaire on the foods they eat regularly which included 15 common soy-based foods including tofu, soy milk, tempeh, tofu burgers, miso soup, drinks containing soy protein, etc. Men who were in the highest category of soy intake ate one half of a serving each day of a soy-based food. Their sperm counts were on average 41 million sperm per milliliter of semen lower than men who ate no soy foods. Normal sperm counts range from 80 to 120 million per milliliter.

This study suggests that soy foods could have a deleterious effect on sperm production and might need to be avoided by men who have low sperm counts if they are trying to conceive children. The study findings may also be another explanation for why sperm counts are dropping worldwide.

Citation: Chavarro JE, Toth TL, Sadio SM, Hauser R. Soy food and isoflavone intake in relation to semen quality parameters among men from an infertility clinic. Hum Reprod. 2008 Nov;23(11):2584-90.