What is "cholesterol"?
Cholesterol is a waxy substance that we find in the bloodstream and actually as part of cells. So it's a part of the fats that are in the body, fats that we call lipids. Cholesterol is actually an important building block of our cells, it's an important part of cell membranes, it's used to make some hormones, as part of our normal biochemistry. So we need to have cholesterol, and the body actually can make its own. On the other hand, we don't need to have excessive cholesterol circulating in our blood. Because if it does circulate in the blood, it gets taken up into our blood vessel walls, and causes the plaque we now refer to as atherschlerosis, or hardening of the arteries. Cholesterol, because it's a fat, can't actually dissolve in blood just the way oil can't dissolve in water. But it's carried around in the blood by special chemicals called lipoproteins. Those lipoproteins are important. You know some of them, probably. We call 'the good cholesterol HDL, or high-density lipoprotein, and that's a lipoprotein that we think of as carrying the cholesterol away from the blood vessel wall and getting rid of it, primarily through the liver. The bad cholesterol, or low-density lipoprotein, LDL, is the lipoprotein that carries cholesterol and acutally allows it to be absorbed into the blood vessel wall, where plaque is then increased in its amount and blood flow through vessels is threatened.
