Study Links Beef to Lower Sperm Count
Beef Industry Disputes Results Showing Beef Diet of Pregnant Moms Affects Sons
March 27, 2007 -- A new study suggests that men whose mothers ate lots of
beef during pregnancy may have lower sperm counts than other men.
The researchers say residues of hormones given to beef to promote growth may
be a factor, but that's not certain.
The beef industry disputes that theory.
"Nothing from this study changes the fact that during pregnancy,
naturally nutrient-rich beef is a vital part of a healthy, wholesome diet for a
mother and her child," Mary K. Young, MS, RD, tells WebMD in an emailed
Young is the executive director of nutrition for the National Cattlemen's
Beef Association (NCBA).
About the Study
The researchers included Shanna Swan, PhD, director of the Center for
Reproductive Epidemiology at the University of Rochester Medical Center in
Their study appears in Human Reproduction.
Swan and colleagues studied 387 men (born between 1949 and 1983) whose
partners were pregnant. The men provided semen samples and completed surveys
about their diet and other lifestyle habits.
The men were also instructed to ask their mothers what they had eaten while
pregnant with them decades earlier.
The moms reported eating four weekly servings of beef during pregnancy, on
Fifty-one moms reported eating beef more than seven times per week during
pregnancy. The average sperm concentration for their adult sons was 24% lower
than men whose moms ate beef less often during pregnancy, the study shows.
In addition, about 17% of men whose moms ate beef more than seven times
weekly during pregnancy had sperm concentrations in the "subfertile"
range, the researchers note.
However, all of the men fathered children without medical treatment,
according to the study.
The study shows no links between other foods eaten during pregnancy and the
men's sperm count. In addition, the men's beef intake as adults wasn't
associated with sperm count.
Hormones have long been administered to U.S. beef cattle to promote cattle
growth, the researchers note.
Traces of such hormones may be more likely to affect fetuses than adults,
Swan's team suggests.
However, the researchers note that they don't have data on hormone residue
in the beef the moms ate during pregnancy.
The FDA, which oversees food safety in the U.S., has information on its web
site about the use of steroid hormones to promote growth in feed animals.
"Certain steroid hormones have been approved for use at very low
concentrations to increase the weight gain and/or improve feed efficiency in
beef cattle," states the FDA.
"Residue levels of these hormones in food have been demonstrated to be
safe, as they are well below any level that would have a known effect on
humans," the FDA says.
Beef Industry Responds
"As a mother and registered dietitian, I can tell you that I am very
confident in the safety of beef," Young tells WebMD.
"It would be unwise to change dietary patterns based on a study of women
trying to recall what they ate at least 20 years ago, especially when iron is
such an important nutrient during pregnancy," Young says.
Iron is found in beef and other foods. "One in five women, and half of
all pregnant women, are iron deficient," Young says.
"Research shows beef actually plays a positive role in men’s
reproductive health, especially the formation of new sperm and maintenance of
sperm motility [movement]," Young says.
Young notes that observational studies -- such as the one done by Swan's
team -- don't prove cause and effect.
Swan's team agrees that its study doesn't prove that beef intake during
pregnancy affects men's sperm. But the researchers say the topic deserves
The mothers' memories of what they ate during pregnancy "is undoubtedly
subject to error," write Swan and colleagues. They call for other studies
to check the findings.
Meanwhile, Swan's study doesn't include any dietary recommendations for