Man's Health and Soy
The Soyfoods Association of North America (SANA) rejects recent media reports that soyfoods may have a harmful effect on male fertility in response to preliminary research presented by Professor Lynn Fraser of King's College London. According to Fraser, who presented her results at the European Society for Human Reproduction and Embryology annual meeting earlier this month, genistein, one of the many forms of isoflavones contained in soyfoods, can negatively impact human sperm's ability to fertilize the female egg. To date, Fraser's findings have not been published in a peer reviewed journal.
"It is unfortunate that the recently reported results of a test tube [experiment] have been interpreted as having an impact on human reproduction," says Nancy Chapman, RD, MPH, Executive Director of SANA. Fraser studied human sperm only as exposed to genistein in a petri dish in a laboratory setting. "Data from animal studies showed that consumption of soy protein has no adverse effect on reproductive performance. These studies show no adverse effects of genistein at human intake levels on reproductive organs, sperm count or sperm motility."
Humans consume genistein as part of a more complex food, not as an isolated compound added to the diet. "It's a different ballgame... if you study only a component of a food in a test tube that is intended to represent that food, you must use the concentration [of the food component] that reaches the human tissue," states Dr. Stephen Barnes, Professor of Pharmacology and Toxicology at University of Alabama at Birmingham. "When testing food, a researcher has to test the [food] substance orally