Supporters of efforts to label GMOs in foods turn out at a rally in Denverin 2013. A ballot measure that would such labels failed to pass by a wide margin Tuesday. Luke Runyon/KUNC/Harvest Public Media hide caption

itoggle caption Luke Runyon/KUNC/Harvest Public Media

Labels on bags of snack foods indicate they are non-GMO food products. This fall, Colorado and Oregon will be the latest states to put GMO labeling on the ballot. Robyn Beck /AFP/Getty Images hide caption

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A customer shops for produce at the Hunger Mountain Co-op in April 2013 in Montpelier, Vt. More than a dozen food cooperatives supported the bill that would require the labeling of genetically modified foods. Toby Talbot/AP hide caption

itoggle caption Toby Talbot/AP

A woman shops at a supermarket in New York City. Spencer Platt/Getty Images hide caption

itoggle caption Spencer Platt/Getty Images