Fat Guide
What is trans fat, and why was it banned?
Unlike saturated and unsaturated fat, trans fat isn't really a natural dietary staple — most of it came from a manufacturing shortcut.
Where trans fat came from
Most artificial trans fat is created through partial hydrogenation — pumping hydrogen into liquid vegetable oil to make it more solid and shelf-stable, historically used in margarine, shortening, and baked goods. The process changes the fat's molecular shape in a way that behaves differently in the body than naturally occurring fats.
Why regulators acted
Research linking artificial trans fat to negative changes in cholesterol (raising LDL while lowering HDL) led U.S. regulators to determine that partially hydrogenated oils were no longer "generally recognized as safe" as a food additive, with final compliance for removing them from the food supply completed in 2018. Many other countries have taken similar regulatory action.
Where trans fat still shows up
Since the ban targeted partially hydrogenated oils specifically, trace amounts of trans fat can still occur naturally in small quantities in some dairy and meat products, and in some imported or shelf-stable packaged foods. Checking labels for "partially hydrogenated oil" in the ingredients list is still a reasonable habit.
Keep reading: Saturated vs. unsaturated fat · What fat actually does · Healthy high-fat foods