Chemistry Talk

carrie0904 · Joined: 15 Aug 2008 Posts: 3

Gents, you might want to stop sipping that soy latte.

A US study has found that eating soy products such as tofu and tempeh, or soy-based meat-free alternatives to mince, sausages and burgers, can have quite a dramatic effect on sperm count. Eating a portion of soy every other day - for example, 115g of tofu, a soy burger or a 240ml glass of soy milk - lowered the sperm count by an average 41 million sperm per millilitre. That’s quite a drop, considering the healthy male produces 80-120 million per ml.

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The results come out of the largest human study to date into the effect of phytoestrogens - plant-derived compounds that mimic oestrogen in the body - on semen quality. The key compounds found in soy are isoflavones, which the Harvard School of Public Health researchers suggest could be adversely affecting sperm production by interfering with the body’s hormone signals.

The Harvard team also found a link suggesting that soy’s effect was strongest in overweight or obese men - possibly because men with more body fat produce more oestrogen. This could be the reason why the men studied seem to be strongly affected by dietary soy, despite consuming 5-10 times fewer phytoestrogens than the average Asian diet. However, regardless of weight, the drop in sperm count seemed to be most pronounced in men with higher natural sperm concentrations. The team urge further randomised trials to determine the true clinical significance of their results.