There are a lot fewer trans fats in today's average American's diet than there were a decade ago, but the Obama administration is moving toward getting rid of them almost entirely.
The Food and Drug Administration (FDA) 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.
To phase trans fat 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.
The FDA reiterated there are no health benefits to trans fats, which are used in processing food and in restaurants, usually to improve texture, shelf life or flavor.
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.
The FDA highlighted this ban is not targeted at trans fats that occur naturally in some meat and dairy products, because they are not considered a major public health threat on their own.
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 flavor 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.
America's 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 percent 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.
The FDA estimates the ban will cost the food industry US$6.2 billion over 20 years as it reformulates products and substitutes ingredients. The benefits will total US$140 billion during the same time period, mostly from lower spending on health care.
Food companies have been switching to mixtures of palm and coconut oils or palm and soybean oils, the combination used in tubs of Country Crock margarine made by Unilever Plc.
Currently, the US market size for palm oil is 1.2 million tonnes annually. Palm oil is already in many products, including Smart Balance peanut butter and spreads, Carotino cooking oil and Luna Bars.
Once trans fats are totally eliminated from the American food supply chain by mid-2018, palm oil imports is expected to only to increase to 1.7 million tonnes a year. This is because most of the artificial trans fat replacement with natural oils and fats are already in place.