In 2012, the interwebs exploded because of an article (pdf) published in Food and Chemical Toxicology by Gilles-Eric Séralini et al. that attempted to show that GMOs cause cancer in rats fed genetically modified corn which is resistant to the herbicide Roundup. They also found similar health problems in rats fed the herbicide alone (along with non-GM feed). The rodents experienced hormone imbalances, along with more and larger mammary tumors, earlier in life, than rats fed a non-GM diet. The authors claimed that the GM- or pesticide-fed rats also died earlier.
Séralini et al. stated that this is the first time GMO corn has been tested for toxicity throughout a rat’s lifespan even though this type of GM corn accounts for more than half of the US crop.
Séralini’s article could have been an important part of the discourse regarding the safety of GMOs – except for a few important problems. Scientists across the world criticized the study for its bad study design, bad statistics, and overhyping of the results.
I personally found the study lacking in basic toxicology methodology, like providing us with dose-response studies, that show us at what level of consumption of the GMO corn would have an effect (if there is one). Of course, Séralini used so few rats in his “study” that it would have been difficult if not possible to develop a dose response.