Take a walk down the grocery store cereal aisle and you’ll see plenty of healthy-sounding brands: Nature’s Path, Peace Cereal, Kashi, Barbara’s Bakery. But not all of them are as natural as they seem, according to a new report. In fact, many (but by no means all) of these brands contain genetically modified ingredients–and in some cases, pesticide residue.

The news comes from the Cornucopia Institute’s Cereal Crimes report (PDF), which examines how big agribusiness is falsely marketing its foods as being natural–an easy thing to do, since unlike certified Organic or Fair Trade, there is no there is no “certified natural” label. And according to Cornucopia, so-called natural brands are priced competitively with organics, even though their ingredients aren’t up to snuff.

So what exactly do companies think that the word “natural” means? Barbara’s Bakery defines it: “All natural means choosing high-quality ingredients to provide optimum nutrition and taste. It means no refined sugar, hydrogenated oils, artificial food additives, flavors or preservatives.” But Cornucopia says that the company uses GMO ingredients. And both Kashi and Bear Naked products contain GMO soy and hexane, a byproduct of gasoline refining and a potential neurotoxin.

Many of the most popular “natural” brands, including Kashi’s, Mother’s, 365, Barbara’s Bakery, and Nutritious Living, contain over 28% GMO ingredients. At least one cereal company–Peace Cereal–used to be organic, but the company switched to cheap conventional ingredients in 2008. Most customers have no idea, of course.