New Proof: GMOs Cause Tumors, Organ Damage, and Premature Death in Rats

The first long-term study shows the devastating effects of Roundup herbicide and genetically modified maize.
Need another reason to buy organic? Rats fed Roundup GMO corn developed tumors and died prematurely. (Photo: G Robert Bishop/Getty Images)
Sep 19, 2012
Megan Bedard is a sucker for sustainable agriculture and a good farmers market, she likes writing about food almost as much as eating it.

If you've ever wondered if the concern over GMOs is just hype, you've now got your answer.

A new study shows that Monsanto's Roundup herbicide and genetically modified maize cause tumors and organ damage in rats.

The French study, published in the peer-reviewed journal Food and Chemical Toxicology, details an experiment in which rats were fed a diet containing NK603 (a seed variety that has been modified to withstand application of the herbicide Roundup) or were given water containing Roundup "at levels permitted in the United States," reports Reuters.

The results? Rats in the study died earlier than rats on standard diets. Of the Roundup group, half of the male and 70 percent of the female rats died prematurely. By comparison, among rats with normal diets, 30 percent of males and 20 percent of females died prematurely. The Roundup rats also experienced mammary tumors and liver and kidney damage. 

Click here to see the study and the disturbing images of the tumor growth in the rats.

While previous studies have demonstrated the ill health effects of genetically modified substances on rats, this particular study was unique in that it tracked the rats throughout their entire lifespan of two years. The authors of the study say their timespan is more realistic, given that it extends beyond the biotech industry's three-month study period, which only follows rats into early adulthood.

This research also indicates that rats do not have to experience high doses of Roundup to experience ill effects, noting that it was "previously known that glyphosate [herbicide] consumption in water above authorized limits may provoke hepatic and kidney failures" but that "the results of the study presented here clearly demonstrate that lower levels of complete agricultural glyphosate herbicide formulations, at concentrations well below officially set safety limits, induce severe hormone-dependent mammary, hepatic and kidney disturbances."

So what's the take-away? As Reuters points out, the lead researcher, Gilles-Eric Seralini of the University of Caen, has a track record of criticizing the biotechnology industry, which may give pause to other researchers. (The authors of the study state there is no conflict of interest.) But undoubtedly, the report raises questions about the safety of genetically modified crops for human consumption.

A chief argument among GMO critics is that at this juncture, we just don't know what genetically modified crops will do to us. As the French report points out, mandatory chronic animal feeding studies aren't required for edible GMOs or formulated pesticides. Meanwhile, our food system is full of them: Estimates suggest nearly 70 percent of processed foods on grocery store shelves contain GMOs

For their part, the authors of the study recommend further research. 

"We propose that agricultural edible GMOs and formulated pesticides must be evaluated very carefully by long term studies to measure their potential toxic effects," the report says.

It's good news for proponents of Prop 37, the California ballot iniative that would require genetically modified foods to be labeled as such. It's likely they just got the boost they need in the run-up to November's vote.

For consumers elsewhere in the country: If you're looking to avoid GMOs, buy foods with a certified organic label. By law, these items can't contain GMOs.

Does this study affect your stance on genetically modified foods? Let us know in the comments section below.

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