NEW YORK—Yesterday morning, I watched as the New York City Health Department voted unanimously to ban the use of trans-fatty acids (trans fats) in all New York City restaurants. The ban will be phased in gradually, but ultimately New York City's eateries will be trans-fat-free. This regulatory move appears to mark the first time a health agency has taken action against safe, legal foods—in this case, certain margarines and cooking oils—instead of disease-causing organisms. The regulatory demonization of trans fats and the underlying "trans-fat-phobia" reveal a good deal about how the media and consumers react to a health scare, how scientists respond (or do not), and what lies ahead for other food ingredients.