Scientists have found that even a small amount of soya products, including meat and dairy substitutes, may have a significant impact on sperm count.
Men who ate an average of half a serving of soya food a day had lower concentrations of sperm than those who did not.
And since low sperm count is known to make it more difficult for a man to conceive, the suggestion is that too much soya in the diet can hinder a man’s chances of having children.
Soya compounds called isoflavones, which mimic the female sex hormone oestrogen, are thought to be behind the effect.
Sperm count ranges between 80 and 120 million sperm per millilitre of semen for normal healthy men.
But researchers in the US found that those with the highest soya intake had average counts of 41 million/ml lower than those of men who did not consume soya products.
Jorge Chavarro at the Harvard School of Public Health in Boston, Massachusetts, US, and his colleagues identified 100 couples seeking treatment for infertility. They studied their lifestyle and were able to identify soya-based foods.
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
The foods in question included tofu, soy sausages, bacon, burgers, soy milk, cheese, yoghurt and ice cream, and other soya products such as roasted nuts, drinks, powders and energy bars.
The research also brought more bad news for overweight or obese men, with the link between soya consumption and sperm count being stronger in that group.
Overweight men may be extra affected because their bodies produce more oestrogen than slimmer people, the researchers believe.
Too much soya affects sperm count
