Soy Foods, Low Sperm Link?

Study Links Soy Foods To Lower Sperm Concentration; Soy Foods Industry Critical Of Study

(WebMD)  Men who eat a lot of soy foods may have a lower sperm concentration than men who don't eat soy foods, according to a new study.

But the study, published online in Human Reproduction, doesn't claim that soy foods are to blame for those lower sperm concentrations, most of which were still in the normal range. Meanwhile, the soy foods industry is drawing attention to the study's limits.

The study's data came from 99 men who visited the Massachusetts General Hospital Fertility Center with their partners between 2000 and 2006.

The men submitted semen samples and completed a questionnaire that included a question about how often they had eaten 15 different soy foods (such as tofu, soy milk, soy burgers, and edamame) and how much of those foods they ate in the previous three months.

Almost all of the men -- 90% -- had sperm concentrations that were within the normal range, and 42% of the men had normal semen analyses, which include sperm shape and motion in addition to sperm concentration.

Most of the men -- 39 of them -- said they hadn't eaten any soy foods during the previous three months. Another 18 men said they ate soy foods less than twice a month, 22 said they ate soy foods between twice a month and twice a week, and 20 said they ate soy foods at least twice a week.

Men who ate soy foods tended to have lower (but still normal, in most cases) sperm concentrations than men who ate no soy foods. That was especially true of overweight and obese men.

Soy foods weren't associated with any other aspects of the semen analyses, such as sperm's shape or movement.

Since the study was a snapshot in time, it doesn't prove that eating soy foods affected the men's sperm concentration; the researchers note that other factors -- including being overweight or obese -- could have been involved. And the men who took part in the study may not be representative of all men.

"The clinical significance of these findings remains to be determined," write the researchers, who included Jorge Chavarro, MD, ScD, ScM, of Harvard School of Public Health's nutrition department.

Soy Foods Industry Responds

WebMD contacted the Soy Foods Association of North America for their response. Nancy Chapman, RD, MPH, the association's executive director, replied by email.

In her email, Chapman notes that the study showed no association between soy foods and "the important measures of sperm quality and male fertility," and she underscores the study's limits noted by Chavarro's team, especially the possibility that extra weight, not soy foods, affected the men's sperm concentration. "Men with high levels of body fat are likely to produce more estrogen than their slim counterparts," writes Chapman. She adds that compared to men who didn't eat soy foods, the men with the highest soy foods intake produced more ejaculate volume but about the same amount of sperm, leading to the lower sperm concentrations.

Chapman also points out that the study was "very small and fails to acknowledge the large normal variation in sperm counts," and that in Asia, where soy foods have been eaten for generations, there haven't been increased medical reports of fertility disorders.

Chavarro's study acknowledges that traditional Asian diets high in soy haven't been shown to harm fertility. But the researchers point out that men in the U.S. and other Western countries are more likely to be overweight and that extra pounds might shift men's sensitivity to phytoestrogens (estrogen-like plant compounds). That theory needs further study, Chavarro's team notes.

What a joke. Look who did this study. Pharmaceuticals
are much worst than soy on sperm. This is more misinformation taking the focus off of the deadly side effects of synthetic drugs.

[Marie Zarankevich]

Everything one eats affects their body in some ways. -- This is not a surprise. -- Subtle effects, resulting from the interactions of all the nutrients we consume, constantly change our biochemistry throughout the day. -- Most of these we adapt to, and continue on with life. -- Nothing to get excited about. -- Soy is still an excellent source of protein, and will continue to be that.

[yongamerica]

Soy products are a natural alternative to milk; a product that is becoming more and more unsafe in today''''s day and age. (Have you ever heard of Mad Soybean Disease?

Give us all a BREAK WHO HAS EVER RECORDED MAD COW MILK?

[yongamerica]

It is a well documented fact that soy products inhibit the production of testosterone. A little bit here and there won''t throw a man''s libido off, but like everything, too much of a good thing can be harmful.

[petesis]

Why is this not surprising?

[dmann991]

Although this report may be correct; we should also remember the positive benefits of soy products. Soy products are a natural alternative to milk; a product that is becoming more and more unsafe in today''s day and age. (Have you ever heard of Mad Soybean Disease?)

[talkingham]

I wonder how these men who claimed to have had no soy products know they haven''t. Soy oil like corn oil is pumped into so may products from potato chips to ice cream. I doubt there are very many people who don''t get a lot more than they realize unless they are dedicated food label readers! And much of the soy and corn oil products are probably made with rancid oils since neither of these "low fat" oil has much in the way of natural preservatives in them.