How High Cholesterol Leads to Atherosclerosis

For decades, news stories and TV ads have hammered it into our heads: Cholesterol is bad for you. (Got the message yet?)

High cholesterol levels lead to clogged arteries in a process called atherosclerosis. Lowering cholesterol lowers the risk of diseases caused by atherosclerosis, like heart attacks and strokes.

What makes cholesterol so bad for your arteries? And isn't there a "good" cholesterol? How does treating high cholesterol help?

Cholesterol and Atherosclerosis: The Bad, the Good, and the Ugly
In cholesterol and atherosclerosis, there are good guys and bad guys:

"Bad" cholesterol, also called low-density lipoprotein (LDL), has chemical properties that can damage arteries. Damaged areas allow more LDL to penetrate artery walls. The LDL gets stuck and accumulates in the artery's wall.

(Warning: chemistry lesson ahead!) Inside the artery wall, free radicals transform LDL from something bad to something worse: oxidized LDL. The cholesterol chemical spill attracts white blood cells and other cells to try to clean up the mess. The cells chew up and digest oxidized LDL.

Once begun, this whole process tends to continue. Over years, the deposit of "bad" cholesterol, cells, and debris grows larger, and it's called a plaque.

"Good" cholesterol, known as high-density lipoprotein (HDL), is the yin to LDL's yang. HDL is on your side: it circulates through your body, acting like a cholesterol magnet. HDL diverts and delivers cholesterol away from your arteries. Much of the cholesterol is either eliminated from the body, delivered to tissues such as the liver, or used to make hormones.

As cholesterol plaques form and grow inside arteries, they eventually can begin to block off blood flow. Here's where atherosclerosis gets ugly.

The LDL-rich center of the plaque can be stable, meaning it grows in a slow, controlled way. The plaque may eventually cause symptoms, but generally speaking, the body adapts. These blockages seldom cause heart attacks.

Plaques can instead be unstable. Remember the cells inside the plaque, digesting all the LDL? As they work, these cells release enzymes that dissolve some of the biological "duct tape" (collagen) holding the plaque together.

Unstable plaques are prone to tearing. If they rupture, they release material that causes a blood clot to form inside the artery. Within minutes, blood flow is cut off. The result: a heart attack or stroke.

Cholesterol Treatment: Down With the Bad, Up With the Good
The link between cholesterol and atherosclerosis led to treatments to improve cholesterol levels. Numerous medications, and changes in lifestyle, can improve cholesterol and reduce atherosclerosis.

Exercise with or without weight loss increases "good" HDL cholesterol and reduces the risk of heart attacks and strokes.

A diet high in fiber and reduced fats can lower "bad" LDL cholesterol. Plant-derived stanols used as fat substitutes also help lower cholesterol.

Statins are the most-often prescribed medicines for high cholesterol. Statins can dramatically lower "bad" LDL cholesterol, by up to 60% or more. They can also increase HDL modestly. In studies, statins reduce the rates of heart attacks, strokes, and death from atherosclerosis.