The Food and Drug Administration says Americans still eat about a gram of trans fat every day, and phasing it out could prevent 20,000 heart attacks and 7,000 deaths each year.
The FDA originally proposed in November 2013 to phase out artificial trans fats over time. The agency says it will make a final decision by June 15.
Five things to know about trans fats and the government's proposed effort to get rid of them:
WORST KIND OF FAT: Scientists say there are no health benefits to trans fats, which are used in processing food and in restaurants, usually to improve texture, shelf life or flavour.
Trans fats can raise levels of "bad" cholesterol and lower "good" cholesterol, increasing the risk of heart disease, the leading cause of death in the United States. Trans fats are widely considered the worst kind for your heart, even worse than saturated fats, which also can contribute to heart disease.
The fats are created when hydrogen is added to vegetable oil to make it more solid, which is why they are often called partially hydrogenated oils.
NO BLANKET BAN: To phase the fats out, the FDA made a preliminary determination in 2013 that trans fats no longer fall in the agency's "generally recognized as safe" category, which covers thousands of additives that manufacturers can add to foods without FDA review. Once trans fats are off that list, any company that wants to use them would have to petition the agency to allow it. That would phase them out almost completely, since not many uses are likely to be allowed.
FDA officials said the agency may phase the fats out more quickly for some foods than others, depending on how easy it is to find substitutes. The FDA has not targeted small amounts of trans fats that occur naturally in some meat and dairy products, because they would be too difficult to remove and aren't considered a major public health threat on their own.
WORST OFFENDERS: Think baked goods, microwave popcorn and fried foods. Over the years, trans fats have been most plentiful in foods like frostings, which need solid fat for texture, or in those that need a longer shelf life or flavour enhancement. Popular foods that have historically contained trans fats are pie crusts, biscuits, microwave popcorn, coffee creamers, frozen pizza, refrigerated dough, vegetable shortenings and stick margarines.
Trans fats also have been used by restaurants for frying. Many larger chains have stopped using them, but smaller restaurants may still get food containing trans fats from suppliers.
MOST OF IT IS ALREADY GONE: The Grocery Manufacturers Association, the main trade group for the food industry, says that food manufacturers have voluntarily lowered the amounts of trans fats in their products by 86 per cent since 2003. Food companies are using other types of oils to replace them.
That reduction was helped along by FDA's decision to force labeling of trans fats on food packages in 2006. There have also been local laws, like one in New York City, banning the fats. Retailers like Wal-Mart have reduced the amount they sell.
INDUSTRY PLANS TO ASK FOR EXCEPTIONS: The Grocery Manufacturers Association is working with food companies on a petition that would ask the FDA to determine if there is a "reasonable certainty of no harm" from some specific uses of the fats. A spokesman for the group would not specify what the industry plans to ask for, but said the FDA encouraged food companies to submit a petition.
The advocacy group Center for Science in the Public Interest first petitioned FDA to ban trans fats 11 years ago. The group's director, Michael Jacobson, praised the industry's efforts so far in reducing the fats but said federal action is necessary.
A phase out would be "the single most important thing the FDA has done about the healthfulness of our food supply," Jacobson said.
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This story has been corrected to show that CSPI first petitioned the FDA 11 years ago, not 9 years ago.