The skinny on trans fat What's trans fat and why are they saying all those terrible things about it?
Trans fat is short for transitional fatty acid: a fat that's in transition from liquid to solid. Bubbling hydrogen through vegetable oils causes them to solidify. It keeps them from going rancid on the shelf and helps them last under the heat of a deep fryer. Some trans fats occur naturally, reports the FDA, but 80% are human-made.
Trans fats were once seen as a healthier alternative to saturated fats. Within the past decade, nutritionists have decided the opposite is true. Where saturated fats merely raise your bad cholesterol, or LDL, trans fats pull a double whammy. They raise LDL while lowering the beneficial type of cholesterol, or HDL.
"Trans fats are particularly hazardous, because they have a dual effect," says Cindy Moore, spokeswoman for the American Dietetic Association and director of nutrition therapy at the Cleveland Clinic Foundation in Cleveland, OH.
Medical studies have linked even small levels of trans fat consumption with coronary heart disease. The FDA projects that adding trans-fat information to nutrition labels will prevent up to 1,200 heart attacks and save up to 500 lives a year.
Because small amounts of trans fats are found in meat and dairy products, it's hard to avoid them completely, reports the Institute of Medicine of the National Academy of Sciences. But the Institute recommends getting your intake as close to zero as possible.
"The desirable level is zero," says Frank Sacks, professor of cardiovascular disease prevention at the Harvard School of Public Health and an advisor to Au Bon Pain. "There's no safe level. It's bad stuff."