A box of Nature Valley Oats ’n Honey granola bars declares that the popular snack is “made with 100 percent natural whole grain oats.” It used to say “100 percent natural.”

Kix cereal once boasted of being made from “all natural corn,” but no more. General Mills edited both labels after the company was accused in a lawsuit of misleading consumers.

The aura that foodmakers hope to convey with the word “natural” is under attack, and Minnesota’s giant food producers have gotten tangled in legal disputes. Cargill is in the midst of at least two lawsuits over natural claims, while General Mills has faced five.

Across the food industry, “natural” has long been one of the most popular labels because it evokes an image of good health. But there are no clear standards for what qualifies, and some argue that the word is so vague that it’s meaningless.

“We can’t define it,” said Urvashi Rangan, a senior scientist and policy analyst for Consumer Reports. “The problem is that it is so subjective. We would just like it to go away.”

The ingredients that go into many items have heightened the debate. Products containing genetically modified (GM) ingredients, such as Kix and Nature Valley bars, have come under particularly fierce attack.

“A lot of lawyers see it as a good field to get into, and one ripe with a lot of misleading claims,” said John Banzhaf, a law professor at George Washington University in Washington, D.C. “The next time a company thinks about slapping a natural label on [a product], their corporate counsel may say, ‘Hey don’t do that.’ ”

Foodmakers continue to put the natural label on new products. More than 20 percent of grocery items launched last year claimed to be “natural” in some way, according to Datamonitor, a market research firm.

Though the use of the natural label has declined slightly in recent years, foodmakers deny that the claim is vague or misleading.

“We stand behind our labels and our products,” General Mills said in a statement. The Golden Valley-based company declined to comment further, saying it normally doesn’t talk about matters under litigation.

Louis Finkel, head of federal affairs for the Grocery Manufacturers Association, a trade group, said foodmakers use natural to accurately represent the products they are selling.

The food companies like the label for its connotation of healthiness, which can command premium prices. According to market researcher Mintel, 62 percent of U.S. adults say that when they see products labeled “all natural,” they think they’re healthy.

But Mintel also found that despite the natural label’s healthy halo, only 33 percent felt they could trust it. And “natural” is often confused with “organic.”

“Consumers are unbelievably confused by natural claims and many attribute the same qualities to natural products that are fully provided by organic foods, ” said Scott Faber, executive director of Just Label It, a group pushing for food containing GM ingredients to be labeled as such.

“Organic” has a detailed definition under federal food regulations. Foods labeled “organic” can’t be produced with synthetic fertilizers and most pesticides, and can’t include GM crops.

The Food and Drug Administration (FDA) has no formal definition of “natural” food, though it considers “natural” on a label to be truthful only when nothing synthetic or artificial is added to a product — an artificial color, for instance. The FDA does not often cite companies for violations.

Consumer groups and corporations have increasingly been looking to the FDA for a better definition. As litigation has piled up, corporate defendants such as General Mills have asked federal judges to effectively defer labeling suits to the expertise of the FDA.

In January, the FDA weighed in on three cases, including a Kix suit. But in a letter to three judges, an FDA assistant commissioner said the agency would not define natural in the context of litigation. If the FDA were to formally define natural, the letter said, it would likely embark on a public rulemaking process.

Such procedures can take years. Plus, the FDA has bigger concerns. “At present, priority public health and safety matters are largely occupying the limited resources that FDA has,” the agency’s letter said.

Few legal precedents

There’s not a long track record of jury verdicts or settlements in natural label litigation, given the relative youth of many suits. But there are some, including a preliminary settlement by Minnetonka-based Cargill in two cases.

The class action suits, filed by two consumers last year in U.S. District Court for Minnesota, took on Cargill’s Truvia zero-calorie sweetener. Made from the leaves of the stevia plant, it’s labeled as natural.

The plaintiffs alleged that natural didn’t apply because Truvia was manufactured using “a multi-step process involving the use of toxic chemicals.” Cargill moved quickly to settle the suits, agreeing to pay $5.3 million and change the labels on Truvia products.

There are five natural labeling lawsuits against General Mills: four involving Nature Valley products, one with Kix cereal. But since the suits were filed, General Mills has changed the labels on the products targeted.

General Mills is not alone. “We have seen companies shift from the label “all natural” to the inherent benefits of what’s in the product,” said Lynn Dornblaser, an analyst at market researcher Mintel.

Take General Mills’ declaration of “100 Natural Whole Grain Oats” on certain Nature Valley bars.

“Whole grain is an easy claim to make; you either have them or you don’t,” Dornblaser said. And oats are natural by pretty much any definition. They’re not grown from GM seed, unlike most of the corn, soybeans and beet sugar produced in the United States. Nature Valley bars can contain corn flour, soy flour and sugar.

Focus on bioengineering

GM ingredients are at the heart of at least 65 class-action labeling suits against foodmakers. The surge follows growing controversy over GM crops.

While regulators and many scientists say GM ingredients pose no food-safety hazards, opposition to GM crop-derived ingredients has spread. Referendums votes to force food companies to label products containing GM ingredients have failed only narrowly in California and Washington state.

The Grocery Manufacturers Association (GMA) plans to petition the FDA to define “natural” as inclusive of GM-derived ingredients. The group plans to push legislation requiring the FDA to do the same. That could shield foodmakers from lawsuits.

The GMA notes that the FDA has never described foods originating from biotechnology as artificial or synthetic. In fact, the FDA has concluded that there’s no significant difference between food stemming from GM crops and traditional crops.

“Products that come from genetic engineered ingredients should not be precluded from being natural, ” said the GMA’s Finkel.

But Faber, of the pro-GM labeling group Just Label It, said GM crops by their very nature don’t seem natural. “Genetic engineering is the essence of doing in a laboratory what nature can’t do on its own.”