What you learned in school
Health and nutrition classes taught that margarine was a healthier alternative to butter because it was lower in saturated fat and cholesterol-free. Students learned that artificial fats were scientifically superior to natural animal fats. Textbooks promoted margarine as a heart-healthy choice without mentioning the hydrogenation process or trans fats. The message was that modern food science had created a better, safer alternative to traditional butter through industrial processing.
What we know now
Health and nutrition classes taught that margarine was a healthier alternative to butter because it was lower in saturated fat and cholesterol. Students learned that artificial fats were better than natural animal fats. Many margarines contained trans fats, which are now known to be more harmful than the saturated fats in butter. Trans fats raise bad cholesterol and lower good cholesterol, increasing heart disease risk. The hydrogenation process that made margarine solid created these harmful trans fats. Butter, while high in saturated fat, is now considered less harmful than margarine containing trans fats.