Beef during pregnancy may harm sperm of sons
Sons born to women who ate a lot of beef during their pregnancy have a 25 percent below-normal sperm count and three times the normal risk of fertility problems, researchers reported Tuesday.
The problem may be due to anabolic steroids used in the United States to fatten the cattle, Dr. Shanna H. Swan of the University of Rochester Medical Center reported in the journal Human Reproduction. It could also be due to pesticides and other environmental contaminants, she added.
If the sperm deficit is related to the hormones in beef, Swan’s findings may be “just the tip of the iceberg,” wrote biologist Frederick vom Saal of the University of Missouri in an editorial accompanying the paper.
In daughters of the beef-eaters, those same hormones could alter the incidence of polycystic ovarian syndrome, the age of puberty and the postnatal growth rate, he said.
“It’s a small effect, but it is a significant effect,” said Dr. Ted Schettler, an environmental health specialist at the Institute for Global Communications in San Francisco. “It’s not surprising. The more you look at dietary factors, the more you turn up interesting information about how diet during pregnancy affects lots of aspects of human health.”
Six growth-promoting hormones are routinely used in cattle production in the United States and Canada: the natural steroids estradiol, testosterone and progesterone, and the synthetic hormones zeranol, trenbolone acetate and melengestrol acetate. At slaughter, not all of these hormones have been metabolized.
Diethyl stilbestrol was also used in the U.S. between 1954 and 1979, when it was banned after tests showed that minks fed chicken waste containing DES became infertile.
The Food and Drug Administration sets limits on how much hormone residue is permissible in beef. Those limits may need to be re-examined if Swan’s findings can be confirmed, vom Saal said.
The use of these hormones in beef was banned in Europe in 1988, and there has been an ongoing dispute between the European Union and the United States about the EU’s attempts to ban imports of U.S. beef containing hormones.
Swan and her colleagues studied 387 partners of pregnant women in five U.S. cities. Each of the men provided a sperm sample and their mothers filled out a questionnaire about their food consumption during pregnancy.
Swan concedes that women may have difficulty recalling their diets more than two decades earlier, but pregnancy may represent an exception. “When you are pregnant, you are very aware of what you eat,” she said.
They found that, in general, the more beef a woman ate, the lower her son’s sperm count. For women who ate beef at least seven times a week, the son’s sperm averaged 24.3 percent below normal. And even though those sons were successful in producing a pregnancy, they were three times as likely to have consulted a fertility doctor before doing so.
The researchers found no link to the mother’s smoking, employment outside the home or number of children she had. There was not enough data on other meats to reveal a potential association.
Swan emphasized that the study needs to be confirmed. She said that it is too soon to recommend that pregnant women not eat beef.