A new study suggests that men who regularly eat soy foods may have lower sperm counts compared to those men who don’t consume soy foods.
Researchers suspect the reason for lower sperm counts is the presences of isoflavones, a chemical compound found in most soy foods that can have a potentially negative effect on reproduction, including a decrease in fertility.
Isoflavones have a similar effect to the human hormone estrogen.
The study data was based on 99 men with fertility-related problems that visited a Boston fertility center between 2000 and 2006.
The men were asked to submit a semen sample and fill out a survey that asked how often they consumed 15-types of soy foods (including soy burgers, soy milk and tofu etc.) and how much soy food they had consumed over the past three months.
Nearly all of the men - about 90 percent – had sperm counts within normal ranges, while 42 percent had normal sperm concentration and analyses, which includes sperm motion and shape.
The men were broken into four groups depending on the amount of soy they had consumed during the previous three months:
39 men had not consumed any soy foods in the past three months.
18 men consumed soy foods less than two times a month.
22 men consumed soy foods anywhere from twice a week to twice a month.
20 men consumed soy at least two times per week.
The study findings are suggestive, but not conclusive, that the the greater the soy intake, the lower the sperm concentration, compared with men who never consume soy foods. The findings are especially true of obese and overweight men.
The significance of the study findings are yet to be established, said Jorge Chavarro, MD, of Harvard School of Public Health’s nutrition department.
Nancy Chapman, RD, MPH, Executive Director of Soy Foods Association of North America issued a statement saying soy foods do not impact sperm count. The study showed no link between soy foods and the measure of sperm quality and male infertility.
The statement also said the study failed to determine what other foods, supplements, medications, environmental factors and sexual activities may have been direct factors attributable to the drop in sperm count.
Past studies have shown that soy foods may help to lower cholesterol, decrease heart disease risk and may help to protect against certain cancers.
“Like most epidemiological reports, this study is retrospective and therefore inherently subjective to a variety of biases,” said Dr. Larry Ross, President of the American Urology Association.
The study is published online in the July issue of Human Reproduction. #