Trans fats are unsaturated fats (i.e., fats with 1 or more double bonds) in which at least 1 of the double bonds is in the trans (instead of the more natural cis) configuration (see diagram below). Trans fats can occur naturally at fairly low levels in some meat and milk products, but most of the trans fats that Americans consume are industrially produced. That is, they are produced from liquid vegetable oils by the process of “hydrogenation”, which results in the creation of solid fats like shortening, margarine, etc.
Examples of cis and trans-configured unsaturated fatty acids. Elaidic acid is the most common trans fatty acid in our food supply. Image from Mozaffarian D, et al. 2006, New England Journal of Medicine (click here for abstract).
