Trans fats do not provide any known benefit, are worse for health than saturated fats, and are not made in significant amounts in natural systems i.e. they are the result of processing by the food industry. Avoid trans fats altogether. Products labelled as having "zero trans fats" CAN AND OFTEN DO contain trans fats; they just keep the serving size low enough so that there is less than 0.5 g of trans fats, which can be rounded down to zero. Any food that does this (says it contains no trans fats but has partially hydrogentated oil in the ingredients) is, from the perspective of health value, lying. From the perspective of the FDA it is fine, but the the FDA has to worry about national economics and lobyists. The only way to stay safe is to READ THE LABEL: Do not buy or eat products containing "PARTIALLY HYDROGENATED VEGETABLE OILS."