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The deadliest form of E. coli is more common than originally thought. Fortunately, grassfed animals are much less likely to transmit the disease.

A study in the March 28th, 2000 issue of the Proceedings of the National Academy of Sciences reports that as many as one out of every three cattle may play host to the deadliest strain of E. coli bacteria ( 0157:H) This is ten times higher than earlier estimates.

As explained in more detail in Why Grassfed Is Best!, feeding cattle their natural diet of grass instead of grain greatly reduces the risk of disease transmission. Why? First, it keeps the overall bacteria count low. Second, it prevents the bacteria from becoming acid resistant. Acid-resistant bacteria are far more likely to survive the acidity of our normal digestive juices and cause disease. The first graph below illustrates the absolute numbers of E. coli bacteria found in grassfed versus grainfed animals. The second graph shows how many of the bacteria are likely to withstand our gastric juices. (Note: Grassfed animals have so few acid-resistant bacteria that the number fails to register on the scale of the graph.)

One of the lead researchers on the project, USDA microbiologist James Russell, told a reporter for Science Magazine, "We were absolutely shocked by the difference. WE never found an animal that didn't agree with the trend."

You should still take the normal precautions when handling and cooking grassfed meat, however. As few as ten E. coli bacteria can cause disease in people with weakened immune systems.

Diez-Gonzalez, F., et al. (1998). "Grain-feeding and the dissemination of acid-resistant Escherichia coli from Cattle." Science 281, 1666-8.

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