A new study suggests that men who regularly eat soy products may be more likely to need infertility treatment.
A link between soy isoflavone compounds and infertility has previously been demonstrated in animal studies, but the latest study in the journal Human Reproduction is one of the first to indicate a similar link in humans.
Researchers studied 99 men and discovered that those who ate the most soy products - such as tofu, tempeh and soy milk - had 41 million sperm per millimetre less than men who did not eat any soy products.
Dr Jorge Chavarro, a research fellow in the department of nutrition at Harvard School of Public Health, US, revealed: "Men in the highest intake group had a mean soy food intake of half a serving per day.
"In terms of their isoflavone content that is comparable to having one cup of soy milk or one serving of tofu, tempeh or soy burgers every other day."
The expert also noted that some of the men involved in the study were eating nearly four whole servings of soy products per day.
At least 20 per cent of couples who are of reproductive age are affected by infertility, and around 30 per cent of men are estimated to be sub-fertile.