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Soy causes infertility


London /AFP
07/01/2005

The genisteine, found in the soy seeds, can jeopardize fertility
Genistein, found in soy, which can mimic the effect of the female hormone estrogen, affects sperm in mice, and have an even stronger impact on human sperm, according to a study by King's College of London.

A study done with human sperm exposed to low levels of genistein, an estrogen-like substance in soy products, showed that the compound damaged sperm in such a way that they became unable to fertilize eggs. It is possible that women who eat soy products may have enough genistein in their system to cause sperm to "burn out" before they encounter an egg.

Once sperm enter an egg a reaction occurs that allows them to fertilize the egg. If this reaction occurs too early, while the sperm are still in the uterus or fallopian tube, then it could cause the sperm to lose fertility.

"On the basis of what we have seen, it might be a practical thing to do if you are in the habit of eating lots of soya-based products to restrict your diet for a short time over the window of ovulation," study's author Lyyn Fraser, told the European Society of Human Reproduction and Embryology meeting.

“ These compounds are classified as environmental oestrogens, but they are very weak, so normally you would expect them to have to be in concentrations around 1,000 times stronger to get a response similar to that prompted by the naturally occurring oestrogen, oestradiol. Yet human sperm are responding to very low concentrations – well within the amounts that have been measured in people's blood.”

Moreover, when the compound is combined with other environmental oestrogens, such as 8-prenylnaringenin (found in hops), and nonylphenol that is found in industrial products like paints, pesticides and cleaning products, the damage to fertility could be even more serious. Researchers now advice women who want to get pregnant to avoid all soy products.