Cholesterol and cholesterol esters are more similar than they are different; however, when considering their similarities several distinctions begin to arise. Cholesterol esters are derived from cholesterol itself. Though both are considered sterols -- a subclass of fat -- cholesterol esters are formed when the body produces enzymes to produce a metabolic reaction with the cholesterol itself.
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Cholesterol is the central steroid compound that forms every cell membrane and tissue in the body. It also plays a key role in the metabolic functions and hormones production. In order to preform its vital roles, however, cholesterol must be transported to the cells via the bloodstream. Cholesterol esters serve to aid in the absorption of cholesterol so it is properly delivered to the cells.
For cholesterol to achieve a specific cellular maintenance routine, it must pass into the cell from the bloodstream. According to an article published in the 2001 issue of the "Journal of Nutrition," cells only take in free cholesterol, that is, cholesterol not bound to esters; however, when cholesterol released from cells, it is mostly in the form of cholesterol esters. While the exact role of cholesterol esters is unclear, they appear to play an import "packaging" role in the passing off cholesterol between high-density and low-density lipoproteins, or HDL and LDL respectively. These two lipoprotein particles are responsible for shuttling cholesterol between cells and the liver, and have long been the focus of atherosclerosis research.
Lipoproteins are classified according to their densities, however, their sizes can vary even within a class. This is especially the case with respect to LDL. While both cholesterol and cholesterol esters make up over half of an LDL particle's mass, their ratios vary in degree. HDL, on the other hand, varies less in proportion due to a protein on its surface that facilitates a conversion to cholesterol esters which contributes to in majority of the HDL particle mass. The variance in LDL size has been a topic of on-going research, but whether variations in size are due to differences in cholesterol and cholesterol ester proportions remains open to further research and debate.
Regardless of dietary intake, approximately 90 percent of cholesterol is synthesized by the liver. Of the cholesterol taken in from dietary sources, however, it first arrives in the form of cholesterol esters. The body still dictates the cholesterol level as it can convert back and forth between the two at will. Cholesterol is an essential for the maintenance of cell membranes, and it is the precursor to several vital steroid hormones, the body has not left its production dependent on diet. According to the "Harvard Family Health Guide," the average individual achieves a 4 to 13 percent reduction in cholesterol levels through dietary modifications alone.