For decades, partially hydrogenated oils loaded with trans fats were darlings of the food industry. Made from regular vegetable oils, they are inexpensive and incredibly useful—they remain a solid at room temperature, extend the shelf lives of processed products, and are a long-lasting deep-frying oil. But the FDA now says the negative health effects of artificial trans fats far outweigh their utility.
Trans fats haven’t been banned yet—the FDA will open the proposal to comments for 60 days—though after that, it will almost certainly remove partially-hydrogenated oils, a main source of trans fats in human diets, from the list of “generally recognized as safe” food ingredients. Food producers could still use the oils in their products, but only after they can prove the ingredients don’t cause any ill health effects. Given the weight of evidence against artificial trans fats, that’s unlikely. (There are some naturally occurring trans fats, mostly from beef and dairy where they appear in trace amounts. Those won’t be affected by the proposal.)
Partially hydrogenated oils were first made in the early 20th century. Most vegetable oils are what’s known as polyunsaturated fatty acids. That means they have many double bonds in their long carbon chains. Animal fats, on the other hand, tend to be fully saturated, meaning they have only single bonds. This helps make them them solid at room temperature. To make vegetable oils behave more like animal fats, scientists developed a technique to “hydrogenate” some of vegetable oils’ double bonds, adding hydrogen atoms to the molecule to convert some of the double bonds to single bonds. In trans fats, one double bond remains in the trans configuration, meaning the carbon chain remains straight. (The other configuration, cis, is kinked at the point of the double bond.)
For decades, products containing trans fats from partially hydrogenated oils were thought to be “healthy.” Studies in the 1960 suggested that they raised cholesterol rates less than those containing saturated fats. It wasn’t until the 1990s that scientists discovered that partially hydrogenated oils were, in fact, worse than saturated fats. Artificial trans fats raise LDL cholesterol—the bad kind—and lower HDL cholesterol—the good kind. In 2006, the FDA began requiring labeling of all artificial trans fats above 0.5 g per serving. Since then, trans fat consumption in the U.S. has dropped from 4.6 g to 1 g per day. Still, the FDA is concerned about the additive effects of residual trans fat consumption.
The new rule could prevent 20,000 heart attacks and save up to 7,000 lives, FDA commissioner Dr. Margaret A. Hamburg told the New York Times. Here’s Sabrina Tavernise, reporting for the Times:
“The artery is still half clogged,” said Dr. Thomas R. Frieden, the director of the disease centers. “This is about preventing people from being exposed to a harmful chemical that most of the time they didn’t even know was there.”
Consumers in recent years have become more aware of the existence of trans fats in products bought from the store, but the half-gram labeling requirement means they can still consume small amounts unknowingly. Many restaurants and fast food chains still use partially hydrogenated oils, too, which can be another way people unwittingly consume them.
In addition to reducing incidence of heart disease, it’s possible that a ban on artificial trans fats could put a small dent in the obesity epidemic, as animal studies have shown higher abdominal fat can result from diets high in partially hydrogenated oils.