Strange science

[Guest guest]

I hadn't noticed a shortage of babies in countries where soya is a

main component of the diet!!!

 

Jo

 

 

Women should avoid eating too much soya if they are trying for a

baby, a UK fertility expert believes.

A study in humans has shown a compound in soya called genistein

sabotages the sperm as it swims towards the egg.

 

Professor Lynn Fraser, from King's College London, said even tiny

doses in the female tract could burn sperm out.

 

She told a European fertility conference that avoiding soya around

women's most fertile days of the month might aid conception.

 

Long swim

 

Genistein is present in all soya-containing products such as soya

milk and many vegetarian foods, as well as some pre-packed meals and

pizzas.

 

Avoiding soya products for a few days a month is worth a try

 

Vegetarian Society

 

Professor Fraser tested what happened to human sperm exposed to the

compound in a dish in the lab.

 

The compound kick-started a reaction in a large proportion of the

sperm that gives them the ability to fertilise an egg.

 

In real life, this does not usually happen until the sperm have been

inside the female for some hours and are close to completing their

long swim towards the egg.

 

Therefore, if women have genistein in and around the womb this could

hamper conception by making sperm peak too soon, believes Professor

Fraser.

 

This could mean they would not be able to fertilise the egg, she told

the annual meeting of the European Society for Human Reproduction and

Embryology.

 

Low concentrations

 

In mice she found it took higher doses of genistein to cause the

reaction, but in humans very small doses were enough.

 

" We were really surprised. Human sperm proved to be even more

responsive than mouse sperm to genistein, responding to very low

concentrations - well within the amounts that have been measured in

people's blood. "

 

She said it was not yet known how much soya might be a safe amount to

avoid this effect.

 

" It's not a question of completely stopping eating products

containing soya.

 

" But it might be best for a woman to avoid them for a few days around

the time she is ovulating. "

 

'Early days'

 

Professor Fraser's previous work in mice showed that compounds

similar to genistein - one found in hop-based products like beer -

effect sperm in the same way.

 

These compounds are all weak oestrogens, but Professor Fraser does

not believe that their action on sperm is the same as the female sex

hormone.

 

Instead, genistein seems to trigger the production of a signalling

molecule in sperm called cyclic AMP.

 

Dr Allan Pacey, Senior Lecturer in Andrology at Sheffield University

and Secretary of the British Fertility Society said: " It's early

days, but clearly if what happens in the laboratory also occurs in

the woman's fallopian tube as the sperm make their way to the egg,

then there would be the potential for fertilisation to fail. "

 

A spokeswoman from the Vegetarian Society said: " For anyone

struggling to become pregnant, avoiding soya products for a few days

a month is worth a try if there is even a slim chance that it will

help increase fertility.

 

" Obviously many vegetarians and vegans use soya in their diet,

however as there are lots of vegetarian and vegan alternatives to

dairy, milk and meat on the market, it shouldn't pose a problem. "