But a new study published this week in the peer-reviewed journal Food and Chemical Toxicology deals a major blow to biotech and chemical company giants. In a first-of-its-kind animal study, French researchers discovered that rats fed genetically engineered corn or exposed to the active ingredient in the weed killer Roundup over a long period died early, suffered mammary tumors, and also had kidney and liver damage. The GMO corn used in the study was Monsanto’s NK603 seed, a variety created to live through heavy dousings of Roundup. Roundup is a systemic pesticide, meaning it’s taken up inside of the plant. It winds up in nonorganic food, particularly processed foods, at levels that many toxicologists say could cause harm to humans.   More from Rodale.com: Farmer’s Market Favorites Under Attack   In the study, researchers fed rats GMO corn or gave them water laced with Roundup at levels allowed in the United States. Compared to the control group, exposed rats developed significantly more mammary tumors and suffered organ damage, and 20% of the males and 50% of females died early. Previous studies linked GMOs—which have been infiltrating the US food system since the 1990s—to allergies and digestive disease.  Surveys have shown that labeling GMOs earns broad bipartisan support among voters. Regardless of political party, about 90% of the population believes GMOs should be labeled. Currently, the only ways to know if your food is GMO- and pesticide-free is to buy organic food. (Want to support labeling efforts? See How You Can Stand Up Against GMOs.) For more surprising news regarding why it’s important to choose organic, see The Truth about Organic.