Think you know what’s in your food? If the past few months are any indication, you might have no idea. In December, the conservation group Oceana found that 39% of seafood purchased in New York City was actually a different species than what the labels claimed. And earlier this year, several European countries were rocked by a horse meat scandal, after it was revealed that the “beef” in certain packaged foods actually hailed from our equine friends.  Gross as it is, this kind of “food fraud” won’t stop anytime soon, according to new research from the United States Pharmacopeia (USP), a non-profit organization that sets standards for the purity of medications and food ingredients. The group manages a database of 2,100 commonly adulterated foods: Whenever a scholarly journal or media outlet reports finding a fraudulent ingredient, the record is added to foodfraud.org. Recently, researchers added 800 new records to the database, mostly gathered from the past two years.  Even though it’s against the law, companies sometimes cut their products with less expensive, unnoticeable fillers. “There could be an infinite number of ways products could be diluted,” says John Spink, PhD, the associate director of Michigan State University’s Anti-Counterfeiting and Product Protection Program. (Curious to see the worst offenders? Brace yourself, then check out our rundown of the country’s 11 Most Fraduluent Foods.)  This latest USP report notes that fraudulent practices have spiked among purveyors of fish, lemon juice, and clouding agents. What should be tuna is often escolar, which is banned in Italy and Japan for its food-poisoning potential, the report warns. Clouding agents—stand-ins for palm oil that give beverages that fresh-squeezed look—are sometimes plasticizers or other phthalates that research has previously linked to cancer and other ailments. How can you make sure your food isn’t fraudulent? Find a retailer you trust, Spink suggests. “They’re going to take great effort to put healthy, safe products on the shelves,” he says. And if you get sick, always report food poisoning to your local health department—keeping tabs on cases helps officials locate the sources of sketchy ingredients. More from Prevention: The Safest Way To Thaw Food Questions? Comments? Contact Prevention’s News Team.