Can soy impact male fertility?

Headlines last week about soy and lowered sperm concentration may have caught your attention and made you rethink soy in your diet. They certainly alarmed me as the mother of a 1-year-old boy who eats soy foods -- such as tofu, tempeh, and veggie dogs -- several times a week.

The study, published in Human Reproduction, found that obese men visiting an infertility clinic who reported eating more soy foods (about 1/2 serving per day) had lower sperm concentrations (not counts) or increased ejaculate volume. Could soy's controversial natural plant estrogens, phytoestrogens, cause hormonal imbalance and infertility? For perspective, I turned to Delicious Living's medical editor, Robert Rountree, MD. Should I eliminate soy from my boy's diet? Here's what he had to say.

I was also concerned when I first read the headlines, but after I dove into the details, I quickly realized that this was a poorly conducted study that based its conclusions on highly questionable assumptions that are not consistent with the scientific consensus (based on a large body of clinical research). The most important point is the study did NOT show that soy lowered sperm count, rather, it appeared to increase the volume of semen, which appeared to slightly decrease the relative concentration of sperm. I don’t think anyone should be concerned about these findings.

Dr. Rountree also attached a press release from the Soyfoods Association of North America, which he found to be an accurate appraisal of the results. It states that: [This] study conflicts with the large body of U.S. government and National Institute of Health-sponsored human and primate research, in which controlled amounts of isoflavones from soy were fed and no effect on quantity, quality or motility of sperm were observed. Upon hearing of Chavarro's findings, Dr. Stephen Barnes, a pharmacologist at the University of Alabama at Birmingham, noted, "This study is the first to find this correlation. The research on soy in men has not found a negative impact on male hormones but rather has suggested a preventive effect in prostate cancer."

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