Healthy food labels are springing up everywhere. In fact, they’ve even been spotted in courtrooms.

At your local Walmart you can find "Great for You" labels on products the store has deemed healthy. A few years ago, some food industry giants tried to launch the Smart Choices campaign, which received much critique for putting their seal of approval on cereals like Fruit Loops. 

Monday on KCUR's Up To Date, Harvest reporter Jessica Naudzianas, food scientist Kanthe Shelke and I discussed how hard it is for consumers to sort through the maze of labels and complex ingredient lists. 

One food label in particular has become the target of a spate of lawsuits across the country.  

The label "Natural" or "100% Natural” is as vague as it is controversial.  We reported earlier on what it means for meat, but when it comes to other foods like granola, cooking oil or chips, the label doesn't have a defined meaning. Basically, other than a few regulations about artificial flavors, it's up to the food companies to decide what's natural.

In recent years consumers have brought suits against Kellogg Company's Kashi Co., Bear Naked granola, ConAgra's Wesson oil, and Pepsico's Frito-Lay for misrepresenting their food product by using “natural” claims. The two cereal lawsuits contend that the makers use "unnatural substances," including potassium bicarbonate, xantham gum, alkali, glycerin and lecithin.

The lawsuits against Wesson Oil and Frito-Lay make a new, different argument. This time, the ingredients in question are the actual corn and the soybean oil, which come from plants grown from genetically modified seeds.

"The legal theory of all these cases is the same: that consumers bought (the products) and bought them at a premium because they said ‘All Natural’ and they were misled by the fact that they included genetically engineered ingredients," said George Kimbrell, a senior attorney with the non-profit Center for Food Safety.

Unlike in the Europe Union, U.S. food manufacturers aren't required to label food that contains genetically modified or biotech ingredients. But these lawsuits argue that genetically engineered foods aren't natural and therefore shouldn't be allowed to wear the “Natural” label.

"This gets to the whole battle over mandatory labeling of GMOs (genetically modified foods) and GE (genetically-engineered) ingredients," said Patty Lovera of the advocacy group Food and Water Watch. She says the suits are indicative of the FDA’s failure to properly define and regulate the “Natural” label.

"If customers are suing companies saying ‘You're misleading me,’ it just shows that this is a minefield in terms of what these labels mean," Lovera said.

But do these suits stand a chance? 

"Absolutely," Kimbrell said. "Certainly the law, as well as common sense, supports the idea that something that is engineered in a lab is not natural in a sense that a reasonable consumer would think it was.

“You're crossing a corn with a microorganism, or a tomato with a fish gene; that is not going to be anyone's sense of something that is natural."

The Center for Food Safety isn't waiting for the final ruling to take action. On behalf of several other organizations and businesses it filed a formal Legal Petition to the FDA to Require Labeling of Genetically Engineered Foods. The group sites polls that show that the majority of Americans believe GE foods should be labeled.

Because there is no federal definition of “natural,” to some degree lawsuits have helped clarify what it can mean. These new suits may change the label’s definition yet again.