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Trans fats are bad, increasing one’s risks of heart disease, sudden death, and diabetes; even, perhaps, aggression. Trans fat intake has been associated with overt aggressive behavior, impatience, and irritability.

Trans fats are basically only found one place in nature—animal fat. The food industry, however, found a way to synthetically create these toxic fats by hardening vegetable oil in a process called hydrogenation, which rearranges their atoms to make them behave more like animal fats.

Although most of America’s trans fat intake has traditionally come from processed foods containing partially hydrogenated oils, a fifth of the trans fats in the American diet used to come from animal products—1.2 grams out of the 5.8 total consumed daily, on average. But, now that trans fat labeling has been mandated, and places like New York City banned the use of partially hydrogenated oils, the intake of industrially-produced trans fat is down to about 1.3. So, that means about 50% of America’s trans fat intake now comes from animal products.

According to the official USDA Nutrient Database, cheese, milk, yogurt, burgers, chicken fat, turkey meat, bologna, and hot dogs contain up to about 1 to 5% trans fats. They also found small amounts of trans fats in non-hydrogenated vegetable oils, due to steam deodorization or stripping during the refining process.

Now, is getting a few percent trans fats a problem, though? The most prestigious scientific body in the United States, the National Academies of Science, concluded that the only safe intake of trans fats is zero. In their report condemning trans fats, they couldn’t even assign a Tolerable Upper Daily Limit of intake because “any incremental increase in trans fatty acid intake increases [coronary heart disease] risk.”

There’s been controversy, though, as to whether the trans fats naturally found in animal products are as bad as the synthetic fats in partially hydrogenated junk food. The latest “study supports the notion that [trans fat] intake, irrespective of source [animal or industrial] increases [cardiovascular disease] risk.” Especially, it appears, in women.

“Because trans fats are unavoidable in ordinary, nonvegan diets,” getting down to zero percent trans fats “would require significant changes in patterns of dietary intake.” One of the authors of the report, the Director of Harvard’s Cardiovascular Epidemiology Program, famously explained why—despite this—they didn’t recommend a vegan diet: “We can’t tell people to stop eating all meat and all dairy products,” he said. “Well, we could tell people to, become vegetarians,” he added. “If we were truly basing this only on science, we would, but it is a bit extreme.” Wouldn’t want scientists basing anything on science now, would we? “Nevertheless,” the report concludes, “it is recommended that trans fatty acid consumption be as low as possible while consuming a nutritionally adequate diet.”

Even eating vegan, though, there’s a loophole in labeling regulations, which allows foods with trans fats that contain up to .5 grams per serving to be listed as having, you guessed it, zero grams of trans fat. “This labeling is misguiding the public by allowing foods to be labeled as ‘trans fat free’ when they are, in fact, not.”

So, to avoid all trans fats, avoid meat and dairy, refined oils, and anything that says “partially hydrogenated” in the ingredients list—regardless of what it says on the Nutrition Facts label.

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