Women who eat soya cut chances of conception by killing sperm

Women trying to conceive should avoid eating soya products at certain times of the month because they can kill sperm, a study has found.

Women trying to conceive should avoid eating soya products at certain times of the month because they can kill sperm, a study has found.

A chemical called genistein, found in soya, causes sperm to "burn out" once they reach a woman's reproductive tract, causing them to lose their fertility before they reach the egg.

Professor Lynn Fraser, of King's College London, found that even small amounts of soya had a rapid and fatal effect on sperm.

Previous studies have shown an effect in mice, but Professor Fraser's latest research, published yesterday, shows that the impact is even greater in humans.

Soya milk is consumed by many as an alternative to dairy products, and is also an ingredient in a range of foods, including meat substitutes, ready meals, chicken soup and chocolate.

Professor Fraser recommended that women avoid eating soya over four days around ovulation, the peak time for conception during a woman's menstrual cycle.

Her team studied the effects of genistein on sperm in laboratory conditions.

The chemical appeared to make the sperm initially "speed up" but they rapidly burnt out before reaching the egg. Within an hour of genistein being introduced, one-third of the sperm had burnt out, a process that normally takes 24 hours.

Genistein is among a number of chemicals that mimic the female sex hormone oestrogen, and it is thought it is this process that "kills" the sperm.