Beware the Myth of Grass-Fed Beef
Cows raised at pasture are not immune to deadly E. coli bacteria.
Check out this Magnum Photos gallery of cows.
On Monday, Huntington Meat Packing Inc. recalled a whopping 864,000 pounds of beef thought to contain a particularly nasty strain of E. coli bacteria called O157:H7. Coming shortly after the recall of 248,000 pounds of beef by National Steak and Poultry on Christmas Eve—and dozens of other scares over contaminated beef and pork—this latest news reminds consumers yet again that the mass production of meat can be very dangerous indeed.
Consumers who still have an appetite for burgers and sirloins have been pushed toward alternative food sources. In particular, they've started to seek out more wholesome meat from animals raised in accordance with their natural inclinations and heritage. According to Patricia Whisnant, president of the American Grassfed Association, there's been a dramatic rise in demand for cattle reared on a pasture diet instead of an industrial feed lot. Grass-fed beef should account for 10 percent of America's beef consumption overall by 2016, she says—a more than threefold increase from 2006.
The comparative health benefits of grass-fed beef are well documented. Scores of studies indicate that it's higher in omega 3s and lower in saturated fat. But when it comes to E. coli O157:H7, the advantages of grass-fed beef are not so clear. In fact, exploring the connection between grass-fed beef and these dangerous bacteria offers a disturbing lesson in how culinary wisdom becomes foodie dogma and how foodie dogma can turn into a recipe for disaster.
Could grass-fed beef ever be afflicted with the sort of E. coli O157:H7 outbreak that led to the December recall? Not according to the conventional wisdom among culinary tastemakers. This idea rose to the top of the journalistic food chain in the fall of 2006, when food activist Nina Planck wrote about the bacteria strain on the op-ed page of the New York Times. At that time, people were getting sick from bad organic spinach, but the contamination seemed to have originated with herds of conventionally raised cattle that lived upstream. Not every animal excretes this nasty type of E. coli, she argued. "It's not found in the intestinal tracts of cattle raised on their natural diet of grass, hay, and other fibrous forage. No, O157 thrives in a new—that is, recent in the history of animal diets—biological niche: the unnaturally acidic stomachs of beef and dairy cattle fed on grain, the typical ration on most industrial farms."
The Times speaks, the world listens. Planck's appraisal of grain- vs. grass-fed beef was highlighted on the Web sites for the Organic Consumers Association, the Center for a Livable Future, Grist, and Culinate.com, among other enviro-foodie venues. A few months later, Hannah Wallace of Salon warned that "a cow's corn diet can also make us sick" on account of the acidic environment it creates for bacteria. Even Michael Pollan, perhaps the most widely read food writer on the planet, explained in a New York Times Magazine piece, "The lethal strain of E. coli known as 0157:H7 ... was unknown before 1982; it is believed to have evolved in the gut of feedlot cattle." These animals, he added, "stand around in their manure all day long, eating a diet of grain that happens to turn a cow's rumen into an ideal habitat for E. coli 0157:H7."
For many consumers, the case was closed: To avoid E. coli O157:H7, just eat grass-fed beef.
Unfortunately, the scientific evidence tells a very different story. Planck's assertion seems to be based on a 1998 report published in the journal Science. In this study, the authors fed three cows a variety of diets in order to ascertain how feed type influenced intestinal acidity in cows and, in turn, how intestinal acidity influenced the concentration of acid-resistant strains of E. coli. They hypothesized that these strains would be especially dangerous to humans, since they could survive the low-pH environment of the human stomach. It turned out that grain-fed cattle did indeed have a much more acidic stomach than those fed grass or hay. And sure enough, they had a million times more acid-resistant E. coli in their colons.
James E. McWilliams is the author of Just Food: Where Locavores Get It Wrong
and How We Can Truly Eat Responsibly and an associate professor of history
at Texas State University.
Illustration by Rob Donnelly. Photograph of beef by Paul J. Richards/AFP/Getty Images.