Genetically modified (GM) crops have been used to feed livestock since 1996, and it now makes up to 90% of all animal feed in the United States. Since this introduction, there has been massive controversy surrounding the safety of this practice. Unfortunately, the validity of the conversation has been sullied by anecdotal evidence and “studies” in journals not subjected to peer review that claim GM food causes a host of physical ailments, including cancer.

However, Alison Van Eenennaam of University of California, Davis, led a comprehensive analysis of studies regarding livestock health between 1983 (13 years before GM crops were introduced) and 2011,which included a total of 100 billion animals collectively eating trillions of GM meals. Ultimately, the study has found that GM feed does not have a negative affect on the animals, and that they are about as nutritionally equivalent as animals who are not fed GM crops. The study was published in the Journal of Animal Science, and will be made open access after October 1.

This study is not the first of its kind, though it is the most inclusive. Alessandro Nicolia of the University of Perugia in Italy published a review last fall of 1,783 papers over a 10 year period that sought to understand the risk of GM crops on the environment. Ultimately, there was no evidence showing GM food poses a significant risk.

Even without this study, common sense would indicate that some of the anecdotal evidence indicating that GM crops cause tumors are overblown. If these farmers are using GM feed as a cost-saving measure, why would they continue to use a product that would kill the animals, and by extension, the bottom line? It is illegal to sell meat from sick animals, so using a product with such harmful (and some would have you believe, common) side effects doesn’t quite compute.

Does this mean that the average farm raising livestock is perfect and impervious to scrutiny? Of course not. Animal rights activists have much to say regarding the living conditions of the animals, the type of food being fed to animals (grass vs. grain, etc.), and “Ag-gag” measures that have turned whistleblowing on factory farms into a criminal offense. Biologists have also expressed concern over the fact that 80% of all antibiotics are given to livestock and that it could lead to catastrophic resistance. Environmentalists would like to see a reduction in the amount of meat eaten to cut down on water and energy waste, as well as reducing methane emissions.

While the conversation about the best practices for raising livestock is far from over, there doesn’t seem to be anything left to talk about in regards to whether or not GM crops are a safe food source for those animals. Ongoing studies regarding their safety will continue, but for now, we should operate on the evidence presented and not on unsubstantiated opinions masquarading as fact.

[Hat tip: Jon Entine, Forbes]