Thursday, March 29, 2007 By Steven Milloy
Consumers were frightened this week by media reports about a new study claiming to link mothers’ consumption of beef with reduced sperm counts in their sons ( "Sperm Count Low if Mom Ate Beef, Study Finds" ). But the study amounts to nothing more than a transparent effort to resurrect an already debunked 1990s-era health scare with appalling science and sensational headlines.
From “Mom’s beef puts son’s sperm count at stake” (Los Angeles Times) to “Meaty momma’s boys lose” (Edmonton Sun, Canada) to “Sunday roasts could have hit male fertility” (Daily Mail, UK), gullible media around the world once again fell for science-by-press-release committed by longtime environmental activist-researchers.
The supposed findings of the study were that “men whose mothers had eaten more than seven beef meals a week had a sperm concentration that was over 24 percent lower than in men whose mothers ate less beef “and that three times more sons of high-beef consumers had a sperm concentration that would be classified as sub-fertile, according to World Health Organization standards, in comparison to men whose mothers ate less beef.”
But for anyone who makes the effort to look past the press releases touting these findings and to examine the study that supposedly backs them up, these findings fall apart as easily as slow-cooked pot roast.
First, the researchers approached the question of what caused the reduced sperm counts exactly backwards. Rather than investigating all possible causes and eliminating those for which there are no supporting evidence, the researchers, according to their own admission, set out to link maternal beef consumption with fertility problems while ignoring other possible causes.
There are myriad causes of infertility. Focusing on a novel one that might make for good headlines — while overlooking established, but less newsworthy, causes — simply does not constitute bona fide scientific investigation.
Then, of course, none of the men studied seemed to have fertility problems in the first place. In fact, the men had all fathered children. But they were nonetheless targeted by the researchers because “[their] rate of consulting a doctor in the past for possible infertility was significantly higher.”
Simply consulting a fertility specialist, however, does not necessarily indicate that a man has fertility problems.
The researchers’ hypothesis is not that beef itself causes infertility, but rather that the hormone-like medicines and chemicals to which cattle may be exposed are at fault. But even if it were true, for the sake of argument, that hormone-like chemicals were linked with male infertility, the researchers would still be obligated to rule out other potential exposures to these chemicals, such as through other foods or occupational exposures in both
the mothers and sons, before blaming beef consumption by mothers.
But the study gets worse.
Although the researchers tout a study size of 387 subjects, only 51 of the sons had mothers who allegedly ate beef more than seven times per week when they were pregnant. So the researchers drew an awfully sweeping conclusion from a minuscule study population.
Moreover, the data on mothers’ beef consumption during 1949 to 1983 were collected by surveying the mothers during 1999 to 2005, as long as 50 years after they were pregnant.
... continues below advertisement:
Such self-reported dietary data were not verified by the researchers and are subject to phenomena known in scientific circles as “recall bias” (memory-impaired responses) or “response bias” (intentionally incorrect responses to, say, avoid embarrassing answers). No one really knows what or how much these women actually ate.
It’s also not necessarily true that more frequent beef consumption is greater beef consumption. Someone who consumes four 8-ounce portions of meat per week consumes 14 percent more beef than someone who consumes a 4-ounce portion every day -- yet, in this study, the everyday-meat eater is assumed to be the greater consumer of beef.
Although the researchers say in their media release, “We don’t have enough information yet to make any recommendations, and this is not what this study was designed to do,” they then proceed to make dietary recommendations including eating only organic beef and generally reducing beef consumption. This study is about causing alarm, not about sound scientific research.
So just who are these researchers and what’s their real beef?
The University of Rochester’s Shanna Swan and Danish researcher Niels Skakkebaek are well-known to followers of the now-defunct 1990s controversy over hormone-like chemicals in the environment, so-called “endocrine disrupters” or “environmental estrogens.”
Swan, Skakkebaek and others have been trying to scare people that man-made chemicals in the environment and food are reducing fertility, particularly sperm counts. Swan has published 15 related studies since 1997 and Skakkebaek has more than 80 related citations in the scientific literature dating back to 1992.
Despite tremendous media attention, the science of Swan and Skakkebaek has never been particularly persuasive. A National Academy of Sciences committee concluded in 1999 that, “Given the evidence to date, increases in the incidence of male reproductive disorders in humans … cannot be linked to exposures to [hormonally-active agents] found in the environment.”
And since there do not appear to be any sort of worldwide fertility problems that cannot be explained by other causes, it’s no wonder that the endocrine disrupter scare never gained traction.
In addition to the news media’s predilection for scary health stories, who, after all, could pass up a story about hamburgers as intergenerational contraceptives? It unfortunately suffers from an abysmal institutional memory, particularly when it comes to science.
So Swan and Skakkebaek can always count on gullible reporters parroting their “findings” as if they were novel, credible and important, rather than what they really are: stale, unbelievable and meaningless.
Steven Milloy publishesJunkScience.comandCSRWatch.com. He is a junk science expert, and advocate of free enterprise and an adjunct scholar at the Competitive Enterprise Institute.
JunkScience.com is updated every weekday. Items from the main page are moved to the archives. Links should be good for at least the date posted. After the posting date, link reliability depends on the policy of the linked sites. Some sites require visitors to register before allowing access to articles. Material presented on this page represents the opinion of JunkScience.com. Copyright -- 1996-2007 JunkScience.com, Inc. All rights reserved on original works. Material copyrighted by others is used either with permission or under a claim of "fair use."