Trans Fat

What Is Trans Fat?

Trans fats are unsaturated fatty acids that contain one or more double bonds in the trans geometric configuration, as opposed to the naturally occurring cis configuration. There are two main sources: industrial trans fats, created by partial hydrogenation of vegetable oils (used in margarines, shortening, and processed foods), and naturally occurring trans fats, produced in small amounts by bacteria in the digestive tracts of ruminant animals and found in beef, lamb, and dairy products.

Industrial trans fats became widespread in the 20th century due to their low cost, long shelf life, and desirable texture properties. By the early 2000s, scientific consensus identified them as uniquely harmful to cardiovascular health.

Health Effects

Industrial trans fats have the most adverse lipid profile of any dietary fat. Consuming them:

• Raises LDL ("bad") cholesterol
• Lowers HDL ("good") cholesterol
• Promotes systemic inflammation
• Is associated with a significantly increased risk of coronary heart disease, stroke, and type 2 diabetes

Naturally occurring trans fats (e.g., conjugated linoleic acid, or CLA, in dairy) do not appear to carry the same risks and may even have modest beneficial effects.

Regulatory Status and Avoidance

The U.S. FDA removed partially hydrogenated oils (PHOs) — the primary source of industrial trans fats — from the Generally Recognized as Safe (GRAS) list in 2018, effectively phasing them out of the food supply. The WHO has called for global elimination of industrial trans fats. Consumers should look for "0 g trans fat" on labels and check ingredient lists for "partially hydrogenated oil."

• Recommended intake: as low as possible — ideally less than 1% of total daily calories
• High-risk foods: commercially fried foods, stick margarines, some packaged cookies, crackers, and pastries