https://en.wikipedia.org/wiki/S%C3%A9ralini_affairWikipedia wrote:The Séralini affair was the controversy surrounding the publication, retraction, and republication of a journal article by French molecular biologist Gilles-Éric Séralini. First published by Food and Chemical Toxicology in September 2012, the article presented a two-year feeding study in rats, and reported an increase in tumors among rats fed genetically modified corn and the herbicide RoundUp. Scientists and regulatory agencies subsequently concluded that the study's design was flawed and its findings unsubstantiated. A chief criticism was that each part of the study had too few rats to obtain statistically useful data, particularly because the strain of rat used, Sprague Dawley, develops tumors at a high rate over its lifetime.
New study is out, found no effect: The GMO90+ project: absence of evidence for biologically meaningful effects of genetically modified maize based-diets on Wistar rats after 6-months feeding comparative trial (I don't quote, it's, as can be expected, quite boring.)