The FDA is requiring food manufacturers to eliminate artificial trans fats in three years. The Post explains what they are and how you can avoid them. (Erin Patrick O'Connor/The Washington Post)

The Food and Drug Administration on Tuesday said it will give manufacturers three years to remove artificial trans fat from the nation’s food supply, a move that the agency estimates could reduce coronary heart disease and prevent thousands of heart attack deaths each year.

“Today’s action is an important step forward for public health, and it’s an action that FDA is taking based upon the strength of the science that we have,” said Susan Mayne, director of the agency’s center for Food Safety and Applied Nutrition.

Tuesday’s announcement won broad praise from public health advocacy groups, such as the Center for Science in the Public Interest, which have long pressed the agency to ban trans fat, and from the American Heart Association, which called the new regulations a “historic victory for the nation’s health.”

“This is great news, and it’s soundly supported by the evidence. There is no one in his right mind who could claim that trans fats are generally regarded as safe,” said Walter Willett, chair of the department of nutrition at Harvard University’s school of public health. “This was really the biggest food processing disaster ever. The human toll has got to be in the millions.”

The Grocery Manufacturers Association, which represents a large swath of the food industry and has expressed concerns over the cost and feasibility of a far-reaching ban on trans fat, said the FDA’s three-year window gives companies time to continue phasing out the substance and reformulate recipes. At the same time, the group said it will petition the FDA to continue to allow small levels of trans fat in certain products, which it argues “is as safe as the naturally occurring trans fat present in the normal diet.”

Many products with artificial trans fats, which are derived from partially hydrogenated oils, have disappeared from grocery stores and restaurant menus in recent years amid widespread agreement about the risks they pose to public health.

Still, experts say the substance lingers in an array of processed foods, from packaged cookies to ready-made frostings, and that even though Americans might only eat small amounts in any product, it can add up to troubling consumption over time.

Since 2006, food companies have been required to include trans fat content information on the Nutrition Facts labels. And between 2003 and 2012, the FDA estimated, consumption of trans fat fell roughly 80 percent.

Trans fat has been around for more than a century but gained popularity in the United States in the 1940s. Over the years, it became a key ingredient in everything from pizzas to microwave popcorn to pancake mix. Food manufacturers embraced trans fats because they provided desirable taste and texture, extended the shelf life of processed foods and were cheaper than animal-based fats such as lard or butter.

As recently as the 1980s, many scientists and public health advocates said that partially hydrogenated oils, which occur when manufacturers add hydrogen to vegetable oil to make a more solid substance, were actually healthier than more natural saturated fats.

But by the mid-1990s, as more studies showed that trans fats were a key culprit in the rising rate of heart disease, public opinion began to shift. In 1994, with dangers posed by trans fats becoming clearer, the Center for Science in the Public Interest petitioned the FDA to require that the substance be listed on nutrition labels. In 2002, the Institute of Medicine found that there was “no safe level of trans fatty acids and people should eat as little of them as possible.”

As a result, intake among Americans declined from 4.6 grams of trans fat per day in 2003 to about one gram per day in 2012, according to the agency.

At the same time, cities such as New York, Boston and Philadelphia imposed bans on artificial trans fats in restaurants. In May 2007, Montgomery County became the first county in the nation to approve a ban on partially hydrogenated oils in restaurants, supermarket bakeries and delis.

Cognizant of consumer demand and the growing body of research about the harm caused by trans fat, food manufacturers have steadily removed the ingredient from the majority of products in recent years. Some of the country’s largest restaurant chains, from McDonald’s to Taco Bell, from Chick-fil-A to Dunkin’ Donuts, have cut trans fat from their menus. Wal-Mart has told its food suppliers to eliminate trans fat.

In late 2013, the FDA took the first steps toward banning the substance altogether, calling it a threat to public health. In a proposal, the agency said trans fats no longer should be among ingredients in the largely unregulated category known as “generally recognized as safe,” or GRAS. Tuesday’s action finalized that proposal, saying trans fats are no longer safe for use in human food.

Companies that want to use trans fat in the future will have to get explicit approval from the FDA and meet rigorous safety standards showing that such use would cause no harm to public health — a steep bar given the mountain of scientific evidence that now exists about the dangers the substance poses.

In an economic analysis published Tuesday, the FDA estimated that the new regulations could cost the industry $6 billion or more over 20 years, but that the savings from reduced medical care and other benefits during the same time could eclipse $130 billion.

“The public health benefits in this action far, far, far outstrip the cost of compliance,” said Michael Taylor, the FDA’s top food safety official. “It’s a very clear case where the benefits far exceed the costs.”