Medical memo: Soy and sperm

Published: June, 2009

Soy has come a long way. Once considered an obscure and inscrutable staple of the far-off Asian diet, it became an icon of American counterculture in the 1960s and '70s, then a prized health food in the decades that followed. Soy has been touted as lowering cholesterol, reducing the risk of heart disease, and protecting the prostate. But studies of these possible benefits have had mixed results at best, and a report from Harvard raises the possibility that dietary soy may lower sperm counts.

The study

The soy study was part of a long-term investigation of environmental factors and fertility. The subjects were 99 male partners of sub-fertile couples. Each man had a medical evaluation and complete semen analysis, and each provided a detailed three-month dietary history that evaluated 15 soy-based foods, ranging from tofu and tempeh to soy milk, veggie burgers, and "energy bars" containing soy protein.

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