“Beware the Myth of Grass-Fed Beef”

Forward by Christopher R. Raines :: Last Friday (22 January 2010) I read an article from Slate.com that I was particularly excited about as it communicated a somewhat similar message as a 06 December 2009 blog post I wrote, “Grass feeding cattle does not ensure beef safety.” In addition to the overarching concern about E. coli O157:H7 (and other STEC’s) is the concern that people may become (or already are) too casual or otherwise complacent when it comes to food safety, banking on  the idea of grass-fed beef being inherently “safer” than “conventional” beef.

What’s more troubling is the information being circulated about the apparent “need” to cook grass-fed beef to lower temperatures.  I have even come across some information equating “well-done” grass-fed beef burgers to mean “cooked to 140°F.”  Not so. In order to help ensure food safety, ground beef, regardless of how the animal was fed, should be cooked to at least 160°F. ::

The article from Slate.com is below.

Beware the Myth of Grass-Fed Beef

Cows raised at pasture are not immune to deadly E. coli bacteria.

By James E. McWilliams Posted Friday, Jan. 22, 2010, at 7:24 AM ET

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 of248,000 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 FutureGrist, 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.

news for grass-fed beef: Eliminate grain from a cow’s diet and you’ll keep its intestines from getting too acidic and spawning dangerous, acid-resistant bacteria. There was only one catch. The authors of the Science piece never specifically tested for E. coli O157:H7. Instead, they guessed that the pattern of O157:H7 growth and induction of acid-resistance would mirror that of E. coli strains that are always living in the colons of cattle. If this assertion were true, E. coli O157:H7 would reach dangerous levels only in gastrointestinal tracts of grain-fed cows.

But between 2000 and 2006, scientists began to take a closer look at the effect of diet on E. coli O157:H7 specifically. A different set of findings emerged to indicate that this particular strain did not, in fact, behave like other strains of E. coli found in cattle guts. Most importantly (in terms of consumer safety), scientists showed in a half-dozen studies that grass-fed cows do become colonized with E. coli O157:H7 at rates nearly the same as grain-fed cattle. An Australian study actually found a higher prevalence of O157:H7 in the feces of grass-fed rather than grain-fed cows. The effect postulated (and widely publicized) in the 1998 Science report—that grain-fed, acidic intestines induced the colonization of acid-resistant E. coli—did not apply to the very strain of bacteria that was triggering all the recalls.

What might explain this discrepancy? Scientists wondered whether there could be two subtypes of E. coli O157:H7 with varying degrees of acid-resistance. By that logic, the microbes from the grass-fed guts would be less resilient—and therefore less dangerous—than the ones that were growing up in the cows reared on grain. So they started running tests to find out.

In 2003, a research team from the University of Idaho reported no difference at all in the levels of acid resistance between E. coli O157:H7 from grass- and grain-fed cattle. (In both cases resistance was high.) Their conclusion stands in direct contrast to the broad claims about grain diets that have been made in the popular press since 2006. It must be that some other factor or factors were responsible for the development of E. coli O157:H7.

Ground beefWe don’t yet know what these might be. But four studies, published between 2003 and 2005, have developed an intriguing hypothesis. Maybe, some reasoned, E. coli O157:H7 behaves differently from other strains because it develops in a different part of the cow’s intricate digestive system. Sure enough, O157:H7 turned out to have a strong tendency to congregate in the recto-anal junction, whereas most other E. coli tend to gather primarily in the colon. Given that, we might presume that the production of E. coli O157:H7 depends more on its unique location than on what its cow host happens to be eating.

The point in dredging up these studies—ones the media never covered—is not to play gotcha with advocates of grass-fed beef. (As mentioned above, grass-fed beef may be healthier than conventional beef over all, and kinder to the animals.) 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 tartar), rare, or medium rare.” Given that the FDA recommends cooking ground beef to 160 degrees to guarantee safety from E. coli, this eat-it-undercooked advice could be dangerous.

When it comes to the intricacies of our food system—and especially the meat industry—what’s true one day can be less true the next. A case in point involves the final FDA report (PDF) on the source of the 2006 E. coli O157:H7 outbreak that motivated Planck to write her seminalTimes op-ed. Released in March 2007, it suggests that the spinach wasn’t contaminated by grain-fed, industrial cattle. Rather, the culprits were more likely to have been wild pigs or pastured (i.e., grass-fed) cattle—animals that were, of course, doing nothing more than eating what they were meant to eat.


5 thoughts on ““Beware the Myth of Grass-Fed Beef”

    • Tonya – I do not know which study is being referenced. I do know of this study, which shows no difference between pasture- and feedlot-fed.
      Journal Applied Microbilogy, 97:2, 362-370.

  1. The benefit of grass fed is that it is still such a niche market that the beef is generally more controlled than typical corn/grain fed from CAFO’s. E-coli is in no way specific to corn fed beef, it is generally an issue of cleanliness and therefore an issue accountability and knowledge on behalf of the producer. Something as simple as apple cider can carry E-coli if the apples are not properly washed or cared for. The bigger issue as I see it from this article is not that Grass fed beef can also make you sick, but that beef that has beef produced 864,000 pounds at a time is produced on such a massive scale that it is almost impossible to gauge the cleanliness of all that beef. And since, in this case, all of those 432 tons of beef were in the form of ground beef it is all the more susceptible to contamination. Every single scrap of beef produced in the U.S. is technically supposed to be screened by an employee of the U.S.D.A., but when working in such high quantities it would be impossible to properly inspect it all. That is why we have created methods like irradiation, where the beef is exposed to radiation in order to kill any potential pathogens. Doing this supposedly makes even the dirtiest beef “safe” to eat. So we find these “solutions” (radiation, recalls) and work on quick fixes rather than going back and saying, “hey, what is wrong with the system in the first place?” Again the problem is not one of whether corn fed or grass fed beef is inherently better than the other, but grass fed beef being produced as it is on such a smaller scale than beef from a feedlot is generally less vulnerable to pathogens than its feedlot counterpart.

    As far as the reference to eating grass fed beef closer to raw, as with steak tartare, The FDA recommends eating all beef cooked to 160 degrees, well-done. This would for the most part eliminate exposure to pathogens, but Steak tartare is made with things like lemon juice, vinegar and salt which have been used for thousands of years as means of preserving foods and killing bacteria. Meats like Salami and prosciutto are never cooked, but are aged carefully and cured with salt which is what makes them edible and not poisonous. If the product you are using is clean to begin with you have less to worry about. Since e-coli is derived from cow feces it can be said that the cows susceptibility to e. coli is not related to its diet, but most pasture raised meats are scrutinized on a closer level by the farmer than the mass produced beef of feedlots. The problem does, and always will come down to the cleanliness and accountability of the producer.

  2. Thank you for this effort at getting at the truth. I read the CDC report you helpfully attached with interest, as the media has been quick to indict beef production, and specifically grain-finished beef, as the obvious source. The primary recommendations of Michael Pollan’s Food Inc. I can agree with — i.e. take greater personal responsibility for your own food selection and preparation . However, the rest of his documentary unfortunately introduced a great deal of misinformation and faulty interpretation of science, particularly the link between cattle feeding and E-coli O157:H7. In a cameo statement, he states that the beef industry has known for over a decade that it could avoid the problem by feeding hay to cattle for a time before they go to slaughter. Of course, he was referring to the study you reference in 1998. That 1998 study and its misuse in Food Inc. and other venues has led to a great deal of grey science by self appointed food watchdogs and those with economic self interest in promoting grass fed beef that leap to policy-significant and self-serving conclusions not supported by that study or intended by its authors. Chief among these is the belief that grass-fed beef is inherently freer of harmful food contaminants, and must be devoid of E-coli o157:H7. (If Michael Pollan says that even grain finished livestock could be flushed of that harmful strain of E-coli by switching to grass for a time before slaughter, then cattle fed exclusively grass all their lives must have never acquired it, right?) As you demonstrate well, leaping to conclusions based on a single piece of work is frought with opportunities for error. Unfortunately Food Inc. failed to weigh the body of work that that study inspired which was available as he made the documentary that limits, contradicts and in other ways fails to replicate the 1998 study.

    Another disturbing logical leap inspired by Food Inc’s gratuitous coopting of that study (although in fairness not one made by by Pollan and the documentary itself) is that since the industry knows that feeding grain is dangerous, producers must only eat grass-fed beef and only sell the inferior kgrain fed to the public. I have seen many variations of that allegation in blogs and other advocacy literature. Simply not true. I’m not wanting to indict grass fed beef or interefere with anybody’s economic freedoms to as a producer or consumer to supply or choose grass fed beef. I just think individual choices and societal choices should be based on sound information and not on Disneyland theme park understandings of agriculture and food safety science.

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