The smooth inside layer of your arteries is pummeled by a variety of things: high blood pressure, cigarettes, excess sugar. When that happens, your body sends lousy LDL cholesterol (remember it by its first initial) to those damaged areas in an attempt to heal the wounds. Your immune cells in the damaged area swallow up the LDL cholesterol and burrow into the inner layer of your arteries. Your body then reacts to the wounds and the cholesterol with a low-grade inflammation. It makes sense: Inflammation is how your immune system deals with many problems, like splinters, unwanted bacteria, insect venom, or other foreign invaders.
Meanwhile, your healthy HDL cholesterol works to clear that LDL cholesterol out of the area. Think of your LDL as a bus carrying loads of hooligans and dropping them off in your arteries to do damage to them, while your HDL serves as a high-speed paddy wagon that zips through your arteries to get the rogue elements off the streets.
More Answers from Michael Roizen, MD