Pregnant women who eat too much beef from cattle treated with growth-promoting hormones may be damaging the future fertility of their unborn sons, scientists suggested yesterday.

New research has shown that men from the United States whose mothers ate beef at least once a day are likely to have lower sperm concentrations than usual, potentially affecting their ability to have children.

Scientists behind the study said it indicated that anabolic steroids and other hormones widely given to American cattle to promote growth could be having an effect on the sexual development of unborn male foetuses.

The findings are not directly relevant to British women, as the hormones implicated by the study were never widely used in the UK, and were banned throughout the European Union in 1988.

They will, however, provide the EU with fresh evidence to support its ban on imported hormone-treated beef, which has been challenged by the US Government, and add to concerns about the effects of envi-ronmental chemicals on male fertility.

Increasing levels of hormones and hormone-mimicking chemicals in the environment, from sources such as pesticides, fertilisers and the con-traceptive pill, have previously been linked to falling sperm counts.

Though the new research points to hormones given to American cattle as another possible factor, it has several important limitations that make the link tentative at best.

The most serious effects were seen only when women ate at least seven beef meals each week, and such levels of consumption are rare among British women.

Sub-fertile sperm counts were measured in only nine men, and none of these was infertile. The research also required women to remember precise details of their diets at least 20 years ago.

Professor Shanna Swan, of the University of Rochester in New York state, who led the study, cautioned that it was applicable only to men from North America born between 1949 and 1983. More research was needed to confirm or refute the hypothesis, she said.

Professor Swan said that the research pointed towards growth-promoting hormones in beef as a likely cause of the men’s lower fertility. “These findings suggest that maternal beef consumption is associated with lower sperm concentration and possible sub-fertility – associations that may be related to the presence of anabolic steroids and other xenobiotics in beef,” she said.

British experts said that the results were of concern. Allan Pacey, a lecturer in andrology at the University of Sheffield, said: “Even though males don’t start producing sperm until puberty, it is during the time in their mother’s womb, and in the early years of their life as an infant, that the testicles develop their capacity to produce sperm.

“That hormones given to cattle might have lowered the sperm counts of adult men because their mothers ate a lot of beef when pregnant, is alarming to say the least. It confirms that Europe was justified to ban their use in cattle production in the mid1980s.”

Alastair Hay, professor of environmental toxicology at the University of Leeds, said that the findings were plausible, but added: “There are major difficulties with this type of study, not least of which is asking a woman how often she ate beef while pregnant 25-30 years ago. We have no idea how much she ate, which would be important to know. At the very least this study should prompt further investigations.”

Red meat risk

— In the study, which is published in the journal Human Reproduction, Professor Swan’s team analysed the semen of 387 men living in the US who were born between 1949 and 1983

— On average, the mothers of the men reported eating 4.3 beef meals per week while they were pregnant, but 51 ate beef seven or more times each week. These women were also more likely to eat large amounts of other red meat, and to have been living in the US when they gave birth

— The sperm counts of men born to this group of heavy beef eaters were on average 24 per cent lower than those of men born to mothers with normal diets

— 17.7 per cent of these men had sperm counts that are classified as sub-fertile according to World Health Organisation guidelines, though this amounted to just nine individuals. The sub-fertility rate among men born to mothers who consumed less beef was 5.7 per cent

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