April 2, 2007 - Men born between 1949 and 1983 to women in the US who ate a lot of beef while pregnant have significantly lower sperm counts, a new study shows.Growth promoters, including sex hormones, used in cattle during this period to increase yield may have damaged prenatal human sperm development, the researchers suggest.

The study involved 387 men and found that men had a 24% reduction in sperm count if their mother ate multiple daily servings of beef while pregnant. Such men were three times more likely to have a sperm count so low they could be classified as sub-fertile.

Shanna Swan at the University of Rochester Medical Center in New York, US, and colleagues recruited among new fathers and asked them to provide sperm samples to determine their sperm count. The men also provided information about how long it had taken them to conceive a child with their respective partners.
 
Swan's team also contacted the men's mothers and asked them to recall how much beef – along with other meats and foods – they consumed while pregnant with their sons.

Of all the foods these women ate, only beef appeared linked to a significant reduction in sperm count among their sons. Around 18% of men born to women who reported eating more than one serving of beef a day while pregnant had sperm counts below 20 million sperm per millilitre, which is classified as "sub-fertile" by the World Health Organization.

By comparison, men whose mothers ate one or fewer portions of beef per day, on average, had higher sperm counts – just 6% were classified as sub-fertile.
The difference between the two groups remained significant after controlling for many external factors such as smoking, sexually transmitted diseases and the amount of beef that the men themselves ate.

Men whose mothers consumed more than seven servings of beef per week while pregnant were also twice as likely to have reported going to consult a doctor for difficulty conceiving a child with their partner than those whose mothers consumed less beef.

Swan suggests that the hormones given to cattle to increase their growth, such as testosterone and progesterone, or the pesticides consumed by these animals might be to blame for the lower sperm counts. The hormones, for example, could interfere with testes development in the womb.

Other scientists agree that this could be a plausible explanation: "Even though males don't start producing sperm until puberty, it is during the time in their mothers' wombs, and in the early years of life as an infant, that the testicles develop their capacity to produce sperm," explains Allan Pacey at the University of Sheffield in the UK.

The European Union banned the use of growth promoters in cattle in 1988, but farmers in the US continue to give them to their livestock. Swan says she hopes to compare the sperm counts of men born in Europe after the ban with their counterparts in the US.
 
Full Story: http://www.newscientist.com/article/dn11479?DCMP=NLC-nletter&nsref=dn11479