A new study published by the American Society for Reproductive Medicine finds that soyfoods and soy isoflavone supplements have no significant effect on male reproductive hormone levels in men. The literature review indicates that soy does not decrease testosterone levels.
Led by Jill M. Hamilton-Reeves, PhD, RD, of St. Catherine's University, St. Paul, Minnesota, researchers assessed the effects of soy protein and soy isoflavones on measurements of male reproductive hormones. Findings, just published online in Fertility and Sterility, a publication of the American Society for Reproductive Medicine, demonstrate no significant effect of soy protein or soy isoflavone intake on circulating levels of testosterone, sex hormone-binding globulin or free testosterone in men.
The comprehensive meta-analysis examined the existing scientific literature including all clinical studies examining soy's effect on male reproductive hormones published before July 1, 2008. Fifteen placebo-controlled treatment groups with baseline and ending measures were analyzed. Thirty-two reports involving 36 treatment groups were also assessed in simpler statistical models. Studies published after July 1, 2008, which were not included in the meta-analysis, support the conclusions of the meta-analysis.
Reproductive endocrinologist William R. Phipps, MD, of the University of Rochester Medical Center, a co-author of the analysis stated, "As a high-quality source of protein that is relatively low in saturated fat, soy can be an important part of a heart-healthy diet and may contribute to a decreased risk of coronary heart disease." He noted that some men have been reluctant to consume soyfoods due to concerns about estrogen-like effects of soy isoflavones, often referred to as phytoestrogens. But according to Phipps, "it is important for the public to understand that there is no clinical evidence to support these ideas. After conducting a comprehensive review of the existing literature, we found no indication that soy significantly alters male sex hormone levels."
Men can benefit from soyfood consumption as a means to meet daily protein requirements and at the same time possibly also reducing their risk of heart disease.
Citing the research study, Lisa Kelly, MPH, RD, of the United Soybean Board, added, "Soy is often praised for the positive role it can play in the diets of women. But, years of clinical research have shown that men stand to benefit from soy, too. I encourage men to incorporate soyfoods into a balanced and varied diet and talk to their healthcare provider about their own unique nutritional needs."
About the United Soybean Board
The United Soybean Board is comprised of 68 farmer-directors who oversee the investments of the soybean checkoff on behalf of all U.S. soybean farmers. For more information on the health benefits of soy and simple recipe suggestions to help add soy to your diet, please visit USB's SoyConnection.com.
Editor's note: To request a copy of the complete report, please email Diana Steeble at [email protected]. Editors of health professional-oriented publications may also wish to refer readers to USB's article for health professionals on this research study, available here.