The relationship between disease, fat intake and lipids levels (like cholesterol) is a complex one.
There is very strong evidence linking disease with fats that are heavily processed such as vegetable oils.
Hydrogenation is a common processing method when cheap oils and converted into solid spreadable fats such as margarine. Heating and chemical manipulation is the process for converting oils into a solid saturated form. One potential by-product of this form of processing is trans fats as whilst they are structurally similar to ‘normal’ unsaturated their fatty acid chains have been distorted by the hydrogenation process.
Studies have shown that dietary trans fatty acids have adverse affects on blood lipid levels promoting an increase of LDL (or bad) cholesterol and a decrease in healthier HDL cholesterol and that this effect is double that produced from the ingestion of saturated fat. It has been estimated that approximately 30,000 premature coronary heart disease deaths annually could be attributed to the consumption of trans fatty acids. The consumption of hydrogenated fats is associated with many other diseases such as cancer, atherosclerosis, diabetes, obesity, immune system dysfunction, and problems with bones and tendons.