"A lot people think it's out of the food supply, but it's still in a lot of places," Christine Johnson Curtis, an assistant commissioner at the department and an author of the study, tells The Salt. It appeared Thursday in the journal Preventing Chronic Disease.

To figure out how stubborn many food companies have been about not removing trans fats, Curtis and her colleagues analyzed a database of 4,340 top-selling packaged foods in the U.S., including baked goods, frozen foods and snacks. The scientists compared the list of actual ingredients to the nutrition label on each package.

Of the products found to still contain the problematic oil, 84 percent were labeled as having 0 grams of it. The FDA allows companies to put 0 grams on the label even if there's up to .5 grams of trans fat in the food.

That may not seem like a lot, but Curtis says that even consuming low levels of trans fats could pose a health risk. "We have established that there's just no benefit to consuming them — they're not healthy for anyone," she says. "But [with a zero gram label], consumers can't know how much they're consuming, and if they're eating multiple products over the course of the day labeled zero trans fat, it could add up."

Of all the food products the researchers looked at, cookies and crackers were the most likely to still contain the oil.

The FDA has not indicated when it will issue a final rule, but Johnson Curtis says she's hopeful food companies will eventually be required to eliminate trans fats entirely.

Copyright 2014 NPR.

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When Zero Doesn't Mean Zero: Trans Fats Linger In Food