A new study of the herbicide glyphosate — the active ingredient in brands such as Roundup, Aquamaster, Glypro and Rascal — shows that it may kill beneficial intestinal bacteria. Harmful bacteria and pathogens, on the other hand, seemed to show high levels of resistance to the herbicide.

The study was conducted by researchers from Leipzig University in Germany and other institutions and was published in the December 2012 issue of the journal Current Microbiology. The researchers set out to determine what happens to the microbiota of poultry when exposed to glyphosate. They exposed both harmful bacteria strains often carried by chickens and other poultry to the herbicide, and then did the same to beneficial bacteria. Live chickens were not used; they performed their tests on cooked meat. The meat was then exposed to various levels of glyphosate.

According to the researchers, three types of salmonella were exposed to glyphosate, as were Clostridium botulinum (the bacterium that causes botulism) and Clostridium perfringens, a common cause of food poisoning. All were "highly resistant to glyphosate," according to the paper.

The researchers then exposed a variety of beneficial intestinal bacteria to the herbicide. These include Enterococcus faecalis, Enterococcus faecium, Bacillus badius, Bifidobacterium adolescentis and species of Lactobacillus, all of which can normally be found in human or animal intestinal tracts. According to the researchers, all of these useful bacteria were susceptible to the herbicide.

Glyphosate and herbicides like it are intended for use on crops to kill weeds, but the researchers say that the presence of the herbicide on food that is consumed could have unintended consequences. They write that "A reduction of beneficial bacteria in the gastrointestinal tract microbiota by ingestion of glyphosate could disturb the normal gut bacterial community." Specifically, they write than an increase in botulism cases could be linked to the toxicity of glyphosate to Enterococcus bacteria, although they do not prove this hypothesis.

Sayer Ji, founder of the website GreenMedInfo.com, wrote that this research reinforces fears that poultry fed genetically modified corn or soybeans — which have been created to be more resistant to glyphosate and therefore could have been more heavily treated with the herbicide — "would likely experience unhealthy changes in the make-up of their intestinal flora (known as dysbiosis), resulting in increasing harm not only to the animals, but to those consuming them. Factory-farmed chickens are already routinely fed antibiotics, arsenic and even antidepressants, all of which represent serious health threats, both by contributing to the generation of communicable disease vectors, as well as contamination of the meat itself."

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Herbicide could make deadly bacteria more dangerous, says new study
Researchers say glyphosate, the main ingredient in Roundup, kills helpful gut bacteria, which may allow botulism and other pathogens to flourish.