According to the U.S. Dietary Guidelines, Americans should keep trans fat consumption as low as possible. Gram-for-gram, trans fat is the most harmful fat of all.
Trans Fat: On the Way out!
Trans fat forms when ordinary vegetable oil is hardened by treatment with hydrogen at high temperatures and pressures. That coverts a liquid into a semi-solid or solid (depending on the degree of hydrogenation) substance that became widely used in margarine, shortening, and countless other processed foods. Until 1990 few studies had shown that trans fat might be harmful to health. But then in the early 1990s careful, reliable clinical studies demonstrated that trans fat raises the "bad" LDL cholesterol, and lowers the "good" HDL cholesterol, in blood, thereby increasing the risk of heart disease. Subsequent research found that trans fat also stiffens arteries and may increase the risk of diabetes. Walter Willett and other epidemiologists at the Harvard School of Public Health estimated that trans fat was causing on the order of 50,000 premature heart-attack deaths each year.
Since 1993, the Center for Science in the Public Interest has sought to reduce the amount of trans fat in food, first by calling on the Food and Drug Administration to require that trans fat be included in Nutrition Facts labels. The FDA required that as of January 1, 2006. But because the evidence of the harmfulness of trans had become incontrovertible, in 2004 CSPI called on the FDA to ban the use of partially hydrogenated vegetable oil. On November 8, 2013, the FDA said it had preliminarily concluded that partially hydrogenated oils were could no longer be considered "generally recognized as safe," a step that could eliminate the ingredient from the food supply within a couple of years.
The amount of artificial trans fat (from partially hydrogenated vegetable oil) being put in our food has declined by more than 75 percent or more since about 2005. That was the result of the scientific research showing that trans fat is the most dangerous type of fat, coupled with massive bad publicity; lawsuits against Kraft (Oreos), McDonald's (French fries), KFC, and Burger King; and FDA's requirement that trans fat be listed on foods labels beginning in January 2006. Most major food manufacturers and chain restaurants have switched from the most harmful fat of all to healthier oils for most of their products.