– Trans fats are formed when a liquid vegetable oil undergoes partial hydrogenation, which transforms the oil into a solid fat, such as margarine. Trans fats, as we all now know, are a panacea to food manufacturers but not great for our health. These particular fats lower the HDL cholesterol in our bodies while simultaneously increasing the LDL cholesterol. Unlike regular margarine, trans-fat free margarines are made by replacing the otherwise high amounts of hydrogenated oil with other ingredients such as mono- and diglycerides and lecithin, among others. I have found this kind of margarine to be an excellent substitute for regular margarine, resulting in flaky pastry and rugelach and cookies that melt in your mouth.