Despite legal bans and doctors’ warnings about trans fat, nearly one in 10 processed food products sold in the United States still contains it, according to a new study released by the Centers for Disease Control and Prevention.

Yet most foods that contain trans fat don't list it on the label, so consumers are unwittingly eating it, according to the research.


Trans fat is made by adding hydrogen to vegetable oil to make it solid. (It's how food processors turn oils into margarine — once, of course, touted as a “health food.”) It helps extend the shelf life of food, but has been linked to a variety of health problems, particularly higher “bad” cholesterol levels and lower “good” cholesterol levels. Even just a few grams a day can have this effect, studies have shown.

Since the first major warnings emerged from doctors and public health authorities about a decade ago, consumption of trans fat has gone way down in the United States. Several states, including California, have banned trans fat from foods sold in restaurants and bakeries.

But trans fat is still lurking, sneakily hidden from product labels.

The new study, by the New York City Department of Health and Mental Hygiene and published in the CDC's journal Preventing Chronic Disease, analyzed the nutritional data of 4,340 top-selling U.S. packaged foods. Researchers found that 391 of those products, or about 9 percent, listed partially hydrogenated oils — the main source of trans fat — in their ingredient list. But 84% of those products claimed to have 0 grams of trans fat per serving on their nutritional label.

Such labeling is allowed under a federal loophole that states that products with fewer than 0.6 grams per serving can claim to have zero trans fat. Here’s where it becomes problematic. A relatively small bag of chips could have up to 0.5 grams of trans fat per serving but contain “three servings.” Thus a consumer could easily devour 1.5 grams of trans fat and not even know it.

The types of products tested included canned soups, tortillas, margarine, salad dressing, frozen pizza, popcorn, salsa, frozen entrees and sides, and cookies – all of which were found to contain trans fat. “Industrial trans fat is still common in U.S. packaged foods” and “most products that contain PHOs are labeled as containing 0 g of trans fat,” the researchers conclude. Removal has not been achieved through the FDA’s current labeling requirements for packaged food, they say. However, in every food category the researchers found alternatives that contained no trans fats.

The researchers urged a government clampdown on trans fats, concluding in their report: “Government efforts to eliminate partially hydrogenated oils from packaged foods will substantially reduce exposure to this known cardiovascular disease risk factor.”

The Food and Drug Administration has tentatively determined that partially hydrogenated oils are not “generally recognized as safe” for consumption. Right now the agency is considering public comments on this determination. If it finalizes its finding, products containing PHOs will not be allowed as ingredients in packaged or restaurant food unless the FDA makes a determination that they are safe.

In the meantime, consumers should be wary of any processed foods, and read labels carefully, public health experts say. Even if a product claims to have 0 trans fat, examine the ingredient list for the words “partially hydrogenated” or the letters “PHO,” which stands for partially hydrogenated oils (unless you’re in a Vietnamese restaurant). 

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