On November 7, 2013, the Food and Drug Administration proposed the elimination of trans fats, or partially hydrogenated oils, which had been linked by Harvard epidemiologists to tens of thousands of deaths before the adoption of mandatory trans-fat labeling in 2006. By revoking the "Generally Recognized as Safe" status from partially hydrogenated oils, the FDA is essentially requiring companies to scientifically prove the oils' safety or find alternatives.

The FDA reiterated its position in June, 2015, changing its proposal to a requirement: companies must phase out artificial trans fats in their products or prove to the FDA that they are safe to use in their products.

While many food companies, including McDonald's, have adopted different oils and fats for their products since labeling was mandated; others have not. Canned frostings, frozen pies, pizzas and pie crusts, canned cinnamon rolls, cookie dough, buttery popcorn, coffee creamer, and some fast-food meals still contain artificial trans fats. Even though trans-fat intake has declined significantly over the past decade, these fats are still deemed a health threat.

Michael Jacobson, executive director of the Center for Science in the Public Interest, a group that has long lobbied for the banning of trans fats, said, "Getting rid of artificial trans fats is one of the most important life-saving measures the FDA could take. Thousands of heart attack deaths will be prevented in the years ahead." So let's take a look at trans fats and a partial timeline leading to the likely end of this demonized fat.

The Fat Family:

Unlike other members of the fat family (saturated, polyunsaturated, and monounsaturated fats), trans fats, or trans-fatty acids, are largely artificial fats. A small amount of trans fats occur naturally in meat and dairy products.

Hydrogenation:

Trans fats are made by a chemical process called partial hydrogenation. Liquid vegetable oil (an otherwise healthy monounsaturated fat) is packed with hydrogen atoms and converted into a solid fat. This made what seemed an ideal fat for the food industry to work with because of its high melting point, its creamy, smooth texture, and its reusability in deep-fat frying.

Shelf Life and Texture:

Partially hydrogenated fats, or trans fats, extend the shelf life of food. They also add a certain pleasing mouth-feel to all manner of processed foods. Think of buttery crackers and popcorn, crispy French fries, crunchy fish sticks, creamy frosting, and melt-in-your mouth pies and pastries. All these foods owe those qualities to trans fats.

Worse Than Butter:

Hydrogenated fats were seen as a healthier alternative to saturated fats: using stick margarine was deemed better for you than using butter, yet numerous studies now conclude that trans fats are actually worse. True, saturated fats raise total and bad (LDL) cholesterol levels. Trans fats do the same, but they also strip levels of good (HDL) cholesterol, the kind that helps unclog arteries. Trans fats also increase triglyceride levels in the blood, adding to our risk of cardiovascular disease.

Many margarines and spreads are now available with low or zero levels of trans fats, but they are less suitable for cooking and baking.

McDonald’s and Trans Fats:

In the early 2000s, McDonald's was the focal point in the campaign to eliminate trans fats. By 2006, the fast-food company cut the amount of trans fat in its chicken products by about 15 percent, but had yet to find a suitable alternative fat for its coveted fries, one that didn’t fundamentally alter the taste.

For allegedly not keeping the public informed of its progress, McDonald’s was sued by BanTransFats.com, the group that sued Kraft Foods, which went on to produce trans-fat-free varieties of Oreo cookies. To settle the suit, McDonald’s agreed to pay $7m to the American Heart Association, and spend a further $1.5m to keep the public informed about reducing trans fats.

Eventually, McDonald's announced in early 2007 that it had begun using a trans-fat-free oil in 1,200 of its 13,700 restaurants, with the rest to follow suit.

But Wendy's Led the Way:

Yet it was America's third-largest burger chain, Wendy's, that was the first of the big fast-food chains to change. Its revamped cooking oil blend reduced trans fats in its chicken and french fries by an average of 95 percent, and even reduced saturated-fat content by an average of 20 percent. KFC removed trans fats from its fried products, though at the time of announcing this in 2006 had yet to find an acceptable alternative for its pot pies and biscuits.

Trans Fats: Going, Going, Gone by 2018

New York City’s Board of Health voted unanimously in December 2006 to ban trans fats in all its 24,000 restaurants, from high-end eateries to fast-food joints, becoming the first city in the United States to impose such a ban. Restaurants were banned from using most oils containing artificial trans fats by July 2007, and were required to eliminate artificial trans fats from all its foods by July 2008.

Starbucks joined the bandwagon and announced in January 2007 that it was eliminating trans fats from its stores in 10 metropolitan areas. It had already begun removing trans fats from some of its baked goods before making the announcement.

Even Girl Scout cookies have gone trans-fat-free.

Many companies are relying on palm oil as a replacement, which is high in saturated fat. Some believe palm oil's particular fatty-acid make-up has heart-healthy qualities, but the jury is still out. Another possible replacement is modified soybean oil. Monsanto is testing a genetically modified soybean oil to make it heart-healthy and suitable for frying, without the need to hydrogenate it.

Food Labels and Trans Fats

While total fat and saturated fat content have routinely appeared on nutrition facts labels for a number of years, the listing of trans fats was not mandatory until 2006.  Before then we had to look for the words "partially hydrogenated …" or "hydrogenated …" in the list of ingredients. The nearer to the top of the list, the higher the level of trans fats; so even when the label didn't offer a trans fat listing, we could make a fair estimate of how much trans fat was lurking inside by looking at the difference between the total fat figure and the saturated and unsaturated fat figures. But few would take the time to do so.

Since 2006 labels have shown the number of grams of trans fats per serving, but not a daily value, as official dietary guidelines fell short of recommending a maximum daily intake for trans fats. The Insitute of Medicine concludes that there is no safe level.

The other wrinkle with the labeling requirement was that products can claim "0 grams of Trans Fat" even if partially hydrogenated fats are listed in the ingredients, so long as a serving size contains less than 0.5g of trans fats. The catch, of course, is that all those fractions of a gram add up if you eat more than a single serving.

The good news is that by 2018, these concerns about trans fats should become a thing of the past.