Insufficient sperm in men maybe due to too much intake of beef by their mothers during their pregnancy, according to a new research.
If pregnant mothers eat too much beef, their sons may have a sperm count about 25 percent below normal and three times the normal risk of fertility problems, researchers at the University of Rochester Medical Center said in a report published in the latest journal Human Reproduction.
The research attribute the lower sperm count to anabolic steroids used in the United States to fatten the cattle.
It could also be due to pesticides and other environmental contaminants, said Dr. Shanna H. Swan who took part in the research.
The finding applies only to North American women, because beef-producing practices vary widely elsewhere, she said.
Swan and her colleagues studied 387 partners of pregnant women in five U.S. cities. Each man provided a sperm sample and his mother filled out a questionnaire about her food consumption during pregnancy.
The mothers were asked how often they ate beef and other meats. On average, they ate beef about 4 times per week, and other meats much less frequently.
The researchers 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 produced a pregnancy, they were three times as likely to have consulted a fertility doctor.
Swan emphasized that the study needs to be confirmed, adding that it is too soon to recommend that pregnant women not eat beef. But if a pregnant woman wants to be cautious, she said, she could switch to organic beef or other high-protein food.
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-Columbia 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.
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.
The use of these hormones in beef was banned in Europe in 1988,and the United States has disputed the EU’s attempts to ban imports of U.S. beef containing hormones.
The Food and Drug Administration limits how much hormone residue is permissible in beef. Those limits may need to be reexamined if Swan’s findings can be confirmed, Vom Saal said. Xinhua