Restaurant giant Chipotle Mexican Grill is endorsing the Colorado ballot measure that mandates labeling of genetically engineered food.

Proposition 105 would require some foods sold in Colorado to carry labels if they contain genetically modified organisms, or GMOs.

The measure would not apply to restaurant food. However, Denver-based Chipotle last year began disclosing GMO ingredients on its online menu. In-store menus are not labeled.

“Fundamentally, we believe that people have a right to know what’s in the food they eat,” Chipotle chairman and co-CEO Steve Ells said in a statement. “Consumers want this information, and we are already giving it to them. But well-funded opposition groups continue to fight labeling efforts, with opponents putting their own profits ahead of consumer preferences.”

Proposition 105 is opposed by corporations such as Monsanto, PepsiCo, Kraft Foods and General Mills, as well as by a broad coalition of Colorado business and agriculture groups.

Supporters include the advocacy group Food Democracy Now and several companies involved in the sale and distribution of organic products.

Opponents through the end of September had raised $9.7 million in campaign funds, nearly 30 times more than proponents’ $334,297.

The measure would require labels stating “Produced With Genetic Engineering” for many packaged foods containing GMOs. Numerous exceptions would exist, including food and drink for animals, alcoholic beverages, prepared foods intended for immediate consumption, restaurant items, and animal-derived foods such as milk, meat and honey, regardless of the animal’s diet.

Much of the corn grown in the U.S. is from seed genetically modified to allow farmers to use broad-spectrum herbicides on their fields. The pervasiveness of food products containing corn, including high-fructose corn syrup, means that hundreds of typical grocery-store items could be subject to the labeling law.

Opponents in campaign literature say that Proposition 105 “is a complex, inconsistent and misleading measure that would impose huge new costs and complicated red tape on farmers, food companies and grocery stores, force Colorado taxpayers to pay millions for more government bureaucracy, and increase grocery bills for Colorado families.”

Chipotle cited a study from Consumers Union showing that for a similar ballot measure in Oregon, a typical consumer would pay about $2.30 more a year.

Chipotle spokesman Chris Arnold said the chain has not contributed to Proposition 105 because corporate policy prohibits political funding.

Co-CEOs Ells and Monty Moran were not listed as contributing personally on campaign filings through Sept. 29.

Chipotle has some food items made with GMO corn, but is working to fully convert to non-GMO corn by the end of the year. Some meats are from animals fed with GMO ingredients, which Arnold said is the “next step” in the chain’s conversion.

Steve Raabe: 303-954-1948, sraabe@denverpost.com or twitter.com/steveraabedp