Soy-based foods may lower sperm count: study

By Julie Steenhuysen

CHICAGO (Reuters) - Eating a half serving a day of soy-based foods could be enough to significantly lower a man's sperm count, U.S. researchers said on Wednesday.

The study is the largest in humans to look at the relationship between semen quality and a plant form of the female sex hormone estrogen known as phytoestrogen, which is plentiful in soy-rich foods.

"What we found was men that consume the highest amounts of soy foods in this study had a lower sperm concentration compared to those who did not consume soy foods," said Dr. Jorge Chavarro of the Harvard School of Public Health in Boston, whose study appears in the journal Human Reproduction.

"It was a relatively large difference," Chavarro said in a telephone interview.

Chavarro said studies in animals have linked high consumption of plant-derived estrogens known as isoflavones with infertility, but so far there has been little evidence of their effect in humans.

"We wanted to know if it would affect sperm production and could serve as a marker for the effects on the reproductive system," Chavarro said.

STRIKING DIFFERENCE

Chavarro's team analyzed the intake of 15 soy-based foods in 99 men who went to a fertility clinic between 2000 and 2006.