James McWilliams, “Beware the Myth of Grass-Feed Beef,” Slate, January 22, 2010

In this article, Slate contributor James McWilliams questions “the conventional wisdom among culinary tastemakers” that pasture-raised cattle does not harbor E. coli O157:H7 at the same levels as conventional livestock. “In fact,” he writes, “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.”

McWilliams traces the misconception to a 2006 New York Times op-ed piece by food activist Nina Planck, who claimed that E. coli was “not found in the intestinal tracts of cattle raised on their natural diets of grass, hay, and other fibrous forage.” According to McWilliams, Planck drew her conclusions from a 1998 report published in Science that found more acid-resistant E. coli in grain-fed cattle, but failed to specifically test for the O157:H7 strain. Further studies have apparently shown that grass-fed cattle “do become colonized with E. coli O157:H7 at rates nearly the same as grain-fed cattle,” while recent research has focused on whether O157:H7 “behaves differently from other strains” in acidic environments because “it develops in a different part of the cow’s intricate digestive system.”

“The point in dredging up these studies—ones the media never covered—is not to play gotcha with advocates of grass-fed beef,” concludes McWilliams. “Instead it’s a warning that advocacy for a trendy food choice might result in a public health hazard. Such a fear is confirmed by consulting the cooking directions provided by many purveyors of grass-fed beef. The home page for one major producer explains that ‘cooking “real food” is not the same as cooking concocted food . . . Grass-fed meats are best when raw (steak tartare), rare or medium rare.’”