The spotlight has fallen on the growth hormones fed to cattle as a possible explanation for low sperm counts in some men. The research, appearing in Human Reproduction, suggests that a mother's high beef consumption (seven or more beef meals per week) while pregnant could be linked to poor sperm quality in her son. Interestingly, beef consumption by the men themselves was not found to be linked to the quality of their semen.
Conducted by researchers from the University of Rochester, study author Shanna H. Swan said this was the first study to examine beef intake and semen quality. Central to the study was the relationship between semen quality and long-term risks from growth hormones and other chemicals in beef. The synthetic growth hormone diethylstilbestrol (DES) was banned in 1979 but other anabolic hormones are still routinely used to raise cattle.
The study found that among the men whose mothers were the highest beef eaters, almost 18 percent had sperm counts classified as "sub-fertile". By comparison, sperm concentrations were 24 percent higher for men whose mothers ate less beef. It seems that high beef consumption during pregnancy may alter sperm production in the male fetus in utero. Swan explained that although sperm production occurs in stages throughout a man's life, the most important stage of development for semen quality actually occurs in the womb.
While there appears to be a significant link between the lowest sperm counts and mothers who were the highest beef consumers, Swan could not pinpoint hormones as the culprit, saying it could be pesticides or other environmental contaminants behind the effect. "What we're really doing here is raising an issue," said Swan. "The average sperm concentration of the men in our study went down as their mothers' beef intake went up. But this needs to be followed up carefully before we can draw any conclusions."
Swan suggests that to gauge the role hormone additives might play; the study should be replicated in European men born after 1988, when hormones were no longer permitted to be used in beef production. And as for how much beef is safe to eat during pregnancy; "We don't have the numbers to identify a 'safe cutoff,'" Swan said, "but it seems to be the very high beef consumption that raises questions."
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Source: University of Rochester Medical Center