Do real men eat soy? Perhaps. But if they want to become fathers, they may want to limit their tofu intake. A new study shows that downing soy products may lower sperm count. The reason, according to the research published in the journal Human Reproduction (pdf): soy beans contain high amounts of phytoestrogens, organic compounds that mimic the female hormone estrogen in the human body and, in animal studies, have been shown to reduce testosterone levels. Lead study author Jorge Chavarro, a research fellow in the Department of Nutrition at the Harvard School of Public Health,and his colleagues found that men who ate at least half a serving a day of soy had, on average, 34 million fewer sperm per milliliter than those who skipped it. But Chavarro doesn't recommend you give up the soy burgers—at least not yet. He notes that the study was limited (99 men) and that more research is needed to prove that tofu actually reduces male fertility.