Yet few people know about its benefits, and even medical experts are still discovering the many roles that it plays.
What Is Cholesterol?
Cholesterol -- a waxy compound that some have likened to soft candle wax -- is a kind of sterol, which is found naturally in the tissues of both plants and animals, though only animals have cholesterol. Your body manufactures much of the cholesterol it needs in the liver, with much smaller amounts produced in the small intestine and in individual cells throughout your body.
Of course, whenever we eat chicken, fish, beef, eggs, dairy or other animal products, we add to our cholesterol levels. We manufacture, though, most of our cholesterol -- about 85%, though estimates vary. Only about 15% comes from food.
The liver packages cholesterol into so-called lipoproteins, which are combinations of lipids (fats) and proteins. Lipoproteins operate like commuter buses that carry cholesterol, other lipids like triglycerides, fat-soluble vitamins and other substances through the bloodstream to the cells that need them.
What's Cholesterol Doing in There?
Cholesterol performs several important functions in the body. Perhaps the most important of these is its role in forming and maintaining cell walls and structures. Cells also need cholesterol to help them adjust to changes in temperature, and it's used by nerve cells for insulation.
Additionally, cholesterol is essential for synthesizing a number of critical hormones, including the sex hormones testosterone, progesterone and estrogen.
Bile, a fluid produced by the liver, plays a vital role in the processing and digestion of fats. To make bile, the liver uses cholesterol. Your body also needs cholesterol to make vitamin D; in the presence of sunlight, cholesterol is converted into vitamin D.
When Good Fats Go Bad
If cholesterol is so necessary, why is it sometimes described as "bad cholesterol," and at other times as "good"? Because, like oil and water, cholesterol and blood don't mix. Cholesterol is an oily, fatty compound that won't dissolve or mix in to blood, which is water-based.
When there's too much cholesterol in the blood, it collects on the inside linings of blood vessels, similar to the way grease and fats poured down the sink collect inside drain pipes. When plaques of cholesterol form inside arteries, it's known as atherosclerosis or "hardening of the arteries," which can lead to strokes and heart disease.
The main culprit in this dangerous process is cholesterol that's packaged into lipoproteins that are less dense with protein and have more fats. These low-density lipoproteins, or LDL, are the "bad" cholesterol that collects in plaques on artery walls.
There's a hero in this tale, though -- and it's also cholesterol. More specifically, cholesterol that's packaged by the liver into lipoproteins that are dense with proteins and have less fat. These high-density lipoproteins, or HDL, are the "good" cholesterol. What's good about HDL is the way it seems to remove plaques of LDL inside arteries, "cleaning" the arteries as it moves through the bloodstream.
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