Mother's Beef Consumption May Affect Son's Fertility

Although none of the men in the study was infertile, 18 percent of those whose mothers ate the most beef had sperm counts classified as "sub-fertile" by the World Health Organization, the researchers said.

"While they (men whose mothers ate high quantities of beef) were fertile, they may have taken a longer time to conceive or, if we had asked them a year before, they might have been having trouble conceiving," Swan said. "They were twice as likely to have visited a doctor because they thought there were problems, so it's not to say there's no effect on fertility."

The study authors don't yet know if anabolic hormones in beef can explain the findings. Most American beef consumed while these women were pregnant was fortified with these hormones, however. Beef also contains residues of pesticides and other industrial chemicals, the study authors said.

Next, Swan and her colleagues hope to repeat this study with men born in Europe after 1988, when such hormones were banned.

"If we did the same study, and there was an association, it couldn't be due to the hormones, because there aren't any," Swan said. "But if we do not see an association, that would actually point to the hormones. That's our plan."

More information

For more on infertility, visit the American Society of Reproductive Medicine.

SOURCES: Shanna Swan, Ph.D., associate chairwoman for research and professor of obstetrics and gynecology, University of Rochester School of Medicine and Dentistry, New York; George R. Attia, M.D., associate professor and director, Division of Reproductive Endocrinology & Infertility, University of Miami Miller School of Medicine; March 28, 2007,Human Reproduction