High maternal beef consumption in pregnancy was associated with significantly decreased sperm concentration in adult male offspring, investigators reported in Human Reproduction.
The study, which included 387 fertile men born between 1949 and 1983 and living in the United States, found that sons of women who ate at least seven servings of beef weekly had a mean sperm count that was 24% lower than did sons of mothers who ate less.
Investigators raised the possibility that the presence of anabolic steroids and other xenobiotics in beef—may have affected the men's testicular development in utero, resulting in lowered sperm counts.
They noted that diethylstilbestrol (DES), the first synthetic hormone, was used in cattle from 1954 to 1979 in the United States. After DES was banned, other anabolic hormones continued to be used legally (Human Reprod. 2007 [Epub DOI:10.1093/humrep/dem068]).
Of the offspring of high beef consumers, almost 18% met the World Health Organization threshold of subfertility (20 million sperm/mL of seminal fluid), compared with 5.7% of the sons of mothers who ate seven or fewer servings of beef per week. This was a statistically significant difference, Shanna Swan, Ph.D., director of the Center for Reproductive Epidemiology at the University of Rochester and her associates wrote.
Between 1999 and 2005, the researchers recruited 773 men born 1949–1983 from five U.S. cities. The men provided semen samples.
Mothers of 387 of the men provided diet information by completing a questionnaire. A total of 26% reported they ate more than seven servings per week of any type of red meat. Thirteen percent said they consumed more than seven servings of beef weekly.
Sons of women who ate more than seven servings of beef per week had sperm concentrations of 43.1 million/mL, compared with 56.9 million/mL in those sons whose mothers ate less beef. This 24% difference was statistically significant. Mothers' consumption of other red meat, fish, chicken, and vegetables were unrelated to their sons' sperm concentrations.
In addition to the higher proportion of men meeting the WHO definition of subfertility, the sons of the high beef consumers also were significantly more likely to self-report previous subfertility (9.8% vs. 5.7%), after adjustment for age.
The researchers noted that self-reporting of beef consumption is likely to be subject to error. In addition, they noted that the steroids in animal feeds might have affected the men as children or adults, and persistent pesticides and industrial chemicals in meat also might play a role. To clarify the role of steroids, the researchers suggested a study of men born in Europe after 1988, when steroids were banned in beef sold and produced there.
In an editorial accompanying the report, Frederick S. vom Saal, Ph.D., of the University of Missouri, Columbia, noted that although DES was banned in the United States in 1979, “administration of combinations of other hormonally active drugs to beef cattle has continued to be a common practice in the [United States].”
He added that, “if xenobiotics are causally involved, the finding of reduced semen quality should be the 'tip of the iceberg,' and other reproductive pathologies should also be observed.”
Dr. Saal urged regulatory bodies to revisit the risks associated with exposure during development to hormonal residues in beef (Human Reprod. 2007 [Epub DOI:10.1093/humrep/dem092]).