Wikipedia: Trans fat, also called trans-unsaturated fatty acids or trans fatty acids, are a type of unsaturated fat that occur in small amounts in nature, but became widely produced industrially from vegetable fats starting in the 1950s for use in margarine, snack food, packaged baked goods, and for frying fast food. Trans fat has been shown to be associated consistently, in an intake-dependent way, with increased risk of coronary artery disease, a leading cause of death in Western nations.

In light of recognised evidence and scientific agreement, nutritional authorities consider all trans fats equally harmful for health and recommend that their consumption be reduced to trace amounts to less than 1% of a person’s diet in 2003 and, in 2018, introduced a 6-step guide to eliminate industrially-produced trans-fatty acids from the global food supply.