TRANS FATS

Trans fatty acids are polyunsaturated or mono-unsaturated fatty acids that can raise LDL-cholesterol (the bad form of cholesterol). And they raise it to the same degree as do saturated fats.
Although chemically they are unsaturated, trans fats have a different configuration of atoms and so behave biologically as if they were saturated.
Humans have been consuming trans fatty acids for centuries, as they occur in butter, milk, beef and lamb.
They are also formed during the manufacture of margarine, when liquid vegetable oils are hydrogenated (hardened) to turn them into a solid spread.
Although still under research, most authorities consider trans fats similar to saturated fats and recommend limiting their intake.