In 2008, I explored in an op-ed the popular belief that switching from grain to grass feeding could be the solution to the problem with E. coli O157:H7 in beef cattle. Flashing forward six years, are we any closer to finding the Holy Grail for on-farm food safety through the diets we feed cattle?

To answer this question, more than another 20 additional pieces of literature were reviewed and are summarized below. The goal in doing this literature review is to help better inform grass-fed producers and consumers about the risks from E. coli O157 whether eating grass-fed or grain-fed beef products.

This piece is not meant to stifle innovation in farming and alternative food markets, or deny positive evidence-based nutritional claims about grass-fed beef. But, it is critically important that food producers, as well as journalists, chefs, and others promoting grass-fed beef, recognize that they have a shared responsibility to provide consumers with accurate information about the safety of beef products. People working in these high profile professions are not expected to understand all of the science, but they should do some honest research and talk to experts in the field before incorrectly downplaying to consumers the risk of E. coli O157:H7 from grass-fed beef.

In a 2010 Slate article (Beware the Myth of Grass-Fed Beef), James E. McWilliams, author of Just Food: Where Locavores Get It Wrong and How We Can Truly Eat Responsibly and a professor of history at Texas State University, wrote on the grass-fed vs grain fed literature. He calls-out a Chef for possibly putting the public at risk by ignoring the science behind food safety and grass-fed beef. Toward the end of the article he says:

“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.”

Mr. McWilliam’s virtually portends an outbreak from grass-fed beef.

In 2014, at least 3 case-patients have developed E. coli O157:H7 infections (including one HUS and death) linked to grass-fed beef sold at Whole Foods and produced by Rain Crow Ranch, also home of the American Grassfed Association (AGA). Patricia Whisnant, Rain Crow Ranch Co-Founder and President of AGA, was quoted on a food blog:

“When that animal, that ruminant, that cow, is fed on grass and maintains a healthy ruminant as it’s supposed to at a neutral pH, then if that E. Coli goes through and for some reason contaminates the finished beef, and is consume by a human, that pathogen is immediately killed by the acid environment of the human stomach.”

Tragically, misinformation about the safety of grass-fed beef and E. coli O157:H7 could lead to a false sense of security among producers, buyers, and consumers, ultimately resulting in illnesses and even death from eating grass-fed beef.

This is what the science actually tells us at this time about grass-fed vs grain-fed beef safety.

  • Cattle are considered the primary hosts of E. coli O157:H7. The organism has been isolated repeatedly from cattle, and implicated as the root cause of outbreaks from beef and dairy products. For this reason, identification of on-farm management practices that would reduce E. coli O157:H7 in cattle reservoirs is an active area of research. Diet has been investigated extensively as a possible pre-harvest intervention, but the research remains inconclusive.
  • In 1998, a study published by Cornell University excited the science and popular media worlds. The researchers suggested that cattle could be fed hay for a brief period before slaughter to significantly reduce the risk of foodborne E. coli infection.  They based this conclusion on a hypothesis that grain feeding increases acid resistance of E. coli in cattle.  Although they showed increased acid resistance in E. coli from grain-fed cattle, only 3 animals were studied (small sample size), and they used “generic” E. coli stains, not pathogenic E. coli O157:H7.
  • The “acid” theory was subsequently debunked in follow-up studies, but has continued as perhaps the most pervasive food safety myth ever. Dietary influences on E. coli O157:H7 shedding and concentration continue to be important areas of pre-harvest food safety research, but recent findings indicate the situation is far more complex and nuanced than the original simplified theory proposed in the widely cited 1998 Science paper.
  • Areas of current research into the role of diet and E. coli O157:H7 in cattle include examination of the influence of distiller’s and brewer’s grains, and different combinations of forage and grains. Intriguing new research shows that the gut ecosystem may play more of a role than the original acid resistance hypotheses.
  • In summary, the scientific evidence at this time still does not support a broad conclusion that grass feeding significantly and consistently reduces the risk of E. coli O157:H7 or other dangerous foodborne pathogens entering the food chain. Consumers should continue to follow recommendations for safe handling and cooking of beef products regardless of whether they are grass-fed or grain-fed.


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