In December, to the delight of many cardiologists and the dismay of many doughnut lovers, the New York City Board of Health voted to ban artificial trans fats from restaurants, school cafeterias, pushcarts, and almost every other food-service establishment it oversees, which includes most everything except hospitals. Trans fats don’t occur naturally in the things people like but feel guilty eating, or at least not at high levels (there are small proportions in the fat in meat and dairy products). But artificial ones are plentiful in commercial foods, because they are easy to use, cheaper than natural fats, and keep practically forever. Trans fats are made by pumping hydrogen gas into liquid fats usually in the presence of nickel so that they will remain solid at room temperature, like butter and lard; and they have the same wonderful properties in pie crusts, cookies, and cakes. Crisco, still generic for solid shortening made by partial hydrogenation (of cottonseed oil), soon became the “sanitary” choice for pie crust and fried chicken, making pastry almost as flaky and skin almost as crisp as lard does.
But starting in the 1970s, a time of general fat panic related to heart disease, trans fats began to look as bad for cholesterol levels as the dreaded saturated fats, and in the 1990s the picture got worse. Trans fats, long-term studies reported, not only raise “bad” cholesterol (LDL); they also lower “good” cholesterol (HDL)—which not even saturated fats do. They look about as bad for the arteries as a fat can be. A 2002 consensus report from the National Academies of Sciences’ Institute of Medicine called the relationship between trans-fat consumption and coronary heart disease “linear” and stated that the only acceptable level of trans fats in the diet was zero. The next year the Food and Drug Administration required food processors to list trans-fat levels on nutrition labels along with saturated fat. When the rule went into effect, in January 2006, public awareness of trans fats went up, and the stage was set for the New York City ban.