Why are trans fats unhealthy?
The exact biochemical methods by which trans fats produce specific health problems are a topic of continuing research. The most prevalent theory is that the human lipase enzyme is specific to the cis configuration. A lipase is a water-soluble enzyme that catalyzes the hydrolysis of ester bonds in water–insoluble, lipid substrates. Lipases thus comprise a subclass of the esterases.Lipases perform essential roles in the digestion, transport and processing of dietary lipids (e.g. triglycerides, fats, oils) in most- if not all- living organisms. The human lipase enzyme is ineffective with the trans configuration, so trans fat remains in the blood stream for a much longer period of time and is more prone to arterial deposition and subsequent plaque formation. While the mechanisms through which trans fats contribute to coronary heart disease are fairly well understood, the mechanism for trans fat's effect on diabetes is still under investigation.
in addition to raising LDL it also lowers HDL (good) cholesterol and raises triglycerides and insulin levels.
When I was a lad margarine was promoted as healthier than butter because it was made with vegetable oil. Likewise sold shortening (Crisco) was promoted as healtheir than lard. Today we know that butter indeed is better for you than trans-fat containing margarine and that lard is healthier than solid vegetable shortening.
My high school chemistry teacher when discussing saturated and unsaturated fats was way ahead of his time when he warned us to avoid hydrogenated oils in 1978.
Because it raises low-density lipoprotein.