AbstractThe regulation of trans fats sets an interesting precedent for the regulation of other legal but harmful food ingredients, such as salt, sugar and saturated fat. In this paper, we distinguish three regulatory measures to reduce such ingredients in food and population intakes: the labelling of an ingredient, a limit on the amount of the ingredient in food products and a ban on the production technology that creates the ingredient. We will compare the regulations promulgated in the US and in the EU to reduce trans fats in food and population intakes. This comparison will identify a common focus on scientific risk assessment and precautionary action but a different orientation towards regulating the internal market and towards producer interests. The comparison also lays bare differences in the regulatory systems of the US and the EU that may inspire US and EU regulators to reflect on possible improvements for future fights against legal but harmful food ingredients.