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How Cholesterol Works: A Brief Overview

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Updated December 20, 2012

Cholesterol is an important molecule in the body, but did you know that most of the cholesterol needed by our bodies is made by our own liver? The remaining cholesterol is obtained through the foods we consume. Persistently high cholesterol levels can be detrimental to our heart and blood vessels, but cholesterol also serves some very important functions in our body, including:
  • serving as a precursor for many hormones, including testosterone and estrogen
  • keeping cell membranes fluid
  • contributing to the formation of bile acids

Where Does Cholesterol Go Once It Is Made?

Once made by the liver, cholesterol is ready to move into the bloodstream and go to various organs and tissues in the body. Once there, cholesterol will perform a variety of functions, which would include strengthening cell membranes, serving as a precursor to all steroid hormones, and composing bile salts to help us to better digest fat.

However, cholesterol does not enter into the bloodstream on its own -- it is too fatty to be absorbed directly into the bloodstream. Therefore, cholesterol must be carried by another protein in order to transport it. The protein that carries cholesterol in the blood is referred to as an apolipoprotein. Apolipoproteins are responsible for transporting cholesterol to its correct destination. When the apolipoprotein and cholesterol molecule are assembled together in the liver, it is now referred to as a lipoprotein.

Lipoproteins occur in different sizes and, depending on their size, perform different functions. One thing to remember is that the more cholesterol and less protein the lipoprotein has, the less stable the molecule will be -- and the more likely you can be at risk for heart disease. There are many types of lipoproteins in the body, and each have an important function:

  • High density lipoproteins, or HDL, are the heaviest lipoproteins and are primarily responsible for carrying cholesterol from various organs and tissues to the liver for recycling or degradation. This is also referred to as the "good" cholesterol and is associated with heart health because they help to clear excess cholesterol from the blood.
  • Low density lipoproteins, or LDL or "bad" cholesterol, are lighter than HDL and are primarily responsible for carrying cholesterol from the liver to organs and tissues of the body. These lipoproteins are less stable because they contain less protein and more lipid, which makes them more prone to breaking apart. Since they don't bring cholesterol back to the liver, they tend to hang around in the blood, sometimes attaching themselves to inflamed vessels. This could eventually cause atherosclerosis, leading to heart disease.
  • Intermediate density lipoprotein, or IDL, are lighter in weight than LDL cholesterol. They are a product of very low density lipoproteins when they are broken down. When IDL is broken down further, it results in LDL cholesterol particles.
  • Very low density lipoproteins are also referred to as the "very bad" cholesterol or VLDL. They are even lighter in weight and are mostly converted to LDL -- but have equally detrimental effects on the circulatory system.
  • Chylomicrons are made in the small intestine and are responsible for transporting triglycerides from the small intestine to different tissues in the body.

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