Trans fats are bad. They may increase one’s risks of heart disease, sudden death, diabetes—and even aggression. Trans fat intake has been associated with overt aggressive behavior, impatience, and irritability.
Trans fats are basically found in only 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. Now that trans fat labeling has been mandated, however, and places like New York City have banned the use of partially hydrogenated oils, the intake of industrial-produced trans fat is down to about 1.3, so about 50 percent of America’s trans fats come now from animal products.
Which foods naturally have significant amounts of trans fat? According to the official USDA nutrient database, cheese, milk, yogurt, burgers, chicken fat, turkey meat, bologna, and hot dogs contain about 1 to 5 percent trans fats. There are also small amounts of trans fats in non-hydrogenated vegetable oils due to steam deodorization or stripping during the refining process.
Is getting a few percent trans fats a problem, though? The most prestigious scientific body in the United States, the National Academies of Science (NAS), 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 may also be no safe intake of dietary cholesterol, which underscores the importance of reducing animal product consumption.