Soy Foods and Lower Sperm Concentration: Is There a Link?
What does the recent study published online by Human Reproduction reveal about soy products and sperm count?
According to news sources, the findings of the recent study concerning soy intake and low sperm count are suggestive but not conclusive. Men who eat a lot of soy products may have a lower sperm concentration than men who don’t eat soy foods, but the study does have its limitations, which have been promptly addressed by the soy food industry.
How was the study involving soy foods and lower sperm concentration conducted?
The study's data was extracted from 99 men who visited the Massachusetts General Hospital Fertility Center with their partners between 2000 and 2006. The participants submitted semen samples and completed a questionnaire that included a question about how often they had eaten 15 different types of soy foods and how much of those foods were consumed in the previous three months. Ninety percent of the men who ate soy foods tended to have lower (but still within the normal range) sperm concentrations than men who ate no soy foods. This was especially true of overweight and obese men.
The study does not prove that eating soy foods affected the men's sperm concentration because researchers noted other factors that could be an influence, namely obesity. It is also true that the men who took part in the study may not be representative of all men. According to Jorge Chavarro, MD, one of the researchers from Harvard School of Public Health’s Nutrition department:
"The clinical significance of these findings remains to be determined.”
Chavarro acknowledges that traditional Asian diets high in soy haven't been shown to harm fertility and that furthers studies are definitely needed.
What were the results of this study connecting soy foods to a lower sperm concentration?
There was an inverse association between soy food intake and sperm concentration that remained significant after accounting for age, abstinence time, body mass index, caffeine and alcohol intake and smoking.
What does the soy food industry have to say about this study?
The executive director of the Soy Foods Association of North America in an email response to WebMD noted that: “the study showed no association between soy foods and the “important measures of sperm quality and male fertility and that men with high levels of body fat are likely to produce more estrogen than their slim counterparts…” She also added that the study was “very small and fails to acknowledge the large normal variation in sperm counts.”
And so it would appear that as far as eating soy and lower sperm counts are concerned, only time and much tofu and other soy-based product consumption will tell.