Would-be mums told to avoid soya

Discussion in 'Food and nutrition' started by TC, Jul 9, 2005.

  1. TC

    TC Guest

    Would-be mums told to avoid soya
    13:05 22 June 2005
    NewScientist.com news service
    Michael Le Page, Copenhagen
    Women trying to conceive should consider not consuming soya for the few
    days around ovulation, according to a UK researcher. Her study shows a
    compound found in soya causes human sperm in a dish to "pop their
    caps" prematurely, rendering them useless. But it remains unclear
    whether eating soya has any actual effect on fertility.
    Lynn Fraser of King's College London studied the effect of very low
    levels of genistein - a compound found in leguminous plants such as
    soya - on human sperm in a liquid medium similar to that found in the
    female reproductive tract. "It was very striking," she says.
    "Within an hour a third of the sperm had gone all the way."
    This means that the genistein had prematurely triggered the sperm to
    undergo what is known as the acrosome reaction. The acrosome is the cap
    on the tip of sperm that contains the enzymes needed to penetrate the
    thick outer layer of the female's egg once the sperm has reached it.
    If it is lost early, sperm have no chance of fertilising an egg.
    Fraser says other studies have shown that genistein gets into the blood
    of people who eat soya products. She believes that in women, it could
    end up in the reproductive tract and damage their chances of
    conceiving. "From what we have seen, women should restrict their diet
    for a short time over the period of ovulation."
    Effects on males
    But other experts are not convinced such advice is necessary. James
    Kumi-Diaka of Florida Atlantic University, US, says his team has also
    found that genistein has a dramatic effect on sperm - so much so that
    he has toyed with the idea of incorporating genistein into condoms as a
    His team has also found that when genistein is injected into male rats
    three times a week, it reduces the size of the litters they father,
    from about 11 pups at most to five. Even low doses had an effect, he
    says. That would seem to hint that men, too, should worry about eating
    soya when trying to father children.
    But Kumi-Diaka stops short of such advice. "It depends on so many
    things," he says. "How the food is prepared, how often you eat it,
    whether it is eaten alone." If genistein really does affect
    fertility, Kumi-Diaka points out, you would expect to see fertility
    problems in Asian countries, where many people consume soya products
    daily - but there is no such evidence.
    Combining chemicals
    Fraser first reported that genistein triggers the acrosome reaction in
    mouse sperm in 2003. In other studies on mouse sperm, she has found two
    other chemicals can also trigger the acrosome reaction. One, called
    8-prenylnaringenin, is found in hops and is thus is present in some
    beers, but Fraser does not know what levels are typical. The second
    chemical, nonylphenol, is found in products such paints, pesticides and
    cleaning products. "There could be a whole range of chemicals with
    this effect," she says.
    What is more, Fraser found that combinations of these chemicals, which
    she calls xenobiotics, had a much greater effect than any one alone.
    "Given the likelihood that we are exposed to several xenobiotics at
    any one time, we need to investigate their possible effects on
    fertility as quickly as possible."
    Her latest studies were presented at a meeting of the European Society
    for Human Reproduction and Embryology in Copenhagen, Denmark, on
    Soy is not real food. And it ain't a healthy food, by anyone's