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Scientists have measured reduced concentrations of sperm in men who included soy in their nutrition. Even the modest amounts of soy foods in regular diet were found to half the sperm count.

After just one portion of soy products every two days, scientists found 41 million fewer sperm per millilitre of semen. They believe it is oestrogens to blame. Plant oestrogens found in foods such as tofu, soy mince or milk are very likely to interfere with hormonal signals.

If this were true, how come all the male Asiats, who eat a lot of soy-based products, experience no fertility problems?

Animal studies showed reduced fertility with soy consumption, while human studies have had contradictory findings.

The Harvard School of Public Health researchers looked at the diets of 99 men with fertility problems. They were divided into four groups depending on how much soy they ate, and when the sperm concentration of men eating the most soy was compared with those eating the least, there was a significant difference.

The average sperm concentration is between 80 and 120 million per milliliter but the men who ate soy on regular basis had around 41 million fewer.

The study author also believes that it is the chemicals isoflavones present in the soy that might be affecting sperm production. Isoflavones have similar effects to the female hormone oestrogen.

Further more, overweight and obese men were found to be even more prone to this effect, reflecting the fact that higher levels of body fat could also be causing increased oestrogen production in men.

If soy had such detrimental effect on sperm production, then men from Asia would be affected the most and experience significant fertility problems. However, there is no evidence that this is the case.

It was previously thought that oestrogenic compounds in food and the environment affect boys exposed in the uterus before birth. The new findings prompt for looking at adult diet more closely although the fact that Asiat men, who have soy food as a major part of their diet, are unaffected suggest that any effect is quite small.


I am growing increasingly interested in the effects of soy on the body. I have been an avid soy milk drinker over the past 3 years due to the many benefits. However I did not become aware of the estrogen components until recently. I wonder what kind of effects this may have on women. I find it interesting that I developed hormonal imbalances during this time.


Hi, I am from Asia and basically I am a vegetarian. If this statement is true, should I stop taking Soy products? I am only 16 and very concern about this statement hope I will get an answer. I personally think that soy products contain a lot of nutritions but a bit anxious about my diet after reading this topic.