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Eating soya could slash men's sperm count

Posted: Tue Oct 16, 2007 5:19 am
by Admin
Men who eat just half a serving of soya a day have drastically fewer sperm than those who do not consume such foods, according to a small, preliminary study.

The study's researchers say larger trials are needed to determine whether men hoping to conceive a child should try to avoid soya foods, such as tofu, tempeh and soya milk. However, soya industry representatives caution that the new findings contradict earlier studies that have shown no impact on sperm count from soya-based products.

Soya foods contain high amounts of isoflavones, compounds that mimic the effects of oestrogen in the body. For this reason, women sometimes increase their intake of soya foods to treat hot flushes caused by declining oestrogen levels in menopause.

Oestrogen-like compounds can also have a dramatic impact on the male body. And previous rodent studies have suggested that high intake of soya products can reduce male fertility. This has led scientists to wonder how isoflavones might influence men's reproductive function, which is highly sensitive to hormones.
Soya survey

Jorge Chavarro at the Harvard School of Public Health in Boston, Massachusetts, US, and his colleagues identified 100 couples seeking treatment for infertility. Researchers asked the men to provide semen samples and complete a questionnaire about their intake of 15 soya-based foods such as miso soup, "power bars", and tofu over the preceding three months.

An analysis of the data, which controlled for factors such as age and weight, revealed that those men who consumed half a serving of soya-based food each day – about the equivalent of half a soya burger – had 65 million sperm per millilitre on average.

That is about 40% less than the typical sperm count of men who do not eat such foods – normally between 80 million to 120 million sperm per millilitre. Men with counts lower than 20 million sperm per millilitre are generally considered infertile.

Chavarro presented the new findings at the annual meeting of the American Society for Reproductive Medicine in Washington, DC on Monday.
Harvesting conditions

Researchers speculate that isoflavones from soya products might lower sperm count by interfering with other hormonal signals that drive sperm production in the testes. They say that further studies are needed to assess whether the drop in sperm count seen in men consuming soya could translate into reduced fertility.

But some experts are sceptical about the new findings. Earlier studies involving men and primates with carefully controlled isoflavone intake have not observed an effect on sperm, according to Stephen Barnes, a toxicologist at the University of Alabama at Birmingham, US, who has studied the influence of soya foods.

The result from Chavarro's study stands in stark contrast to previous findings. "It doesn't fit in with the rest of what has been done experimentally," says Barnes. "But that's not to say it's wrong," he adds.

Industry representatives also note that because isoflavone content in a given food can vary widely based on harvesting conditions, it is difficult to draw conclusions about the impact of soya from retrospective surveys of food consumption.
Obesity link

"Unless researchers are measuring the actual isoflavone content it would be difficult to know the impact of soya foods on sperm count," says Nancy Chapman, executive director of the Soyfoods Association of North America based in Washington, DC. "When you do an observational trial like this there could have been other behaviours causing this decline in sperm count."

Chavrro admits that many east Asian men consume much more soya than the participants in his trial and do not develop fertility problems.

He speculates that his study found a link between soya and low sperm count because many of the participants were overweight or obese. Men with high levels of body fat produce more oestrogen than their slim counterparts. "They already have a lot of background estrogen," says Chavarro.

He believes that the oestrogen-mimicking isoflavones in soya might push the hormonal levels in overweight and obese men even higher, to the point at which sperm begin to suffer.

* 12:17 16 October 2007
* news service
* Roxanne Khamsi, Washington DC

Posted: Tue Oct 16, 2007 1:30 pm
by volleyball_man
Hi people,

I had to chime in here.

I drink a cup or two of soy milk every day or so. I eat soy beans on my salads a lot. I have done this for years.

Both times my wife and I decided to try and conceive - we were successful on the first try. I was 37 on the conception of child number one and 40 on the conception of child number two. I might be a rare exception, but my experience definitely contradicts the proposition of this study.


Posted: Wed Oct 17, 2007 4:15 am
by Bri3626
VB! Missing in action. How you been doing?

Posted: Wed Oct 17, 2007 4:38 am
by volleyball_man
Hey Man,

I'm good. Still working out. I've been doing the 12wk CF startup for some 4 weeks now. I am getting the knowledge together for affiliation with CF. My wife and I are thinking of opening a combo gym/healthfood restaurant.

I am giving my elbows some rest from all of the pullups. I keep PU in my workout via the CF warmup - but only to make sure I don't completely lose them. After I get through with the 12wk program, I'll try an L2D3 and see how I do.

Posted: Thu Oct 18, 2007 7:12 am
by Bri3626
Very nice.

good to know your still plugging away!

Posted: Sun Oct 28, 2007 2:55 pm
by gwmccull
Given this news, I believe I'll be increasing my soy intake. Hopefully this'll lower the chance of any accidents with my fiance! javascript:emoticon(':D')