"Good" Vs. "Bad" Cholesterol

Why is LDL cholesterol considered "bad"?
A high level of low-density lipoprotein, or LDL cholesterol, reflects an increased risk of heart disease. That's why LDL cholesterol is often called "bad" cholesterol. Lower levels of LDL cholesterol reflect a lower risk of heart disease. When too much LDL cholesterol circulates in the blood, it can slowly build up in the walls of the arteries that feed the heart and brain. Together with other substances it can form plaque, a thick, hard deposit that can clog those arteries. This condition is known as atherosclerosis. If a clot (thrombus) forms where a plaque is, the blood flow can be blocked to part of the heart muscle, causing a heart attack. If a clot blocks blood flow to part of the brain, a stroke results.

Why is HDL cholesterol considered "good"?
About one-third to one-fourth of blood cholesterol is carried by high-density lipoprotein (HDL). HDL cholesterol is known as the "good" cholesterol because a high level of HDL cholesterol seems to protect against heart attack. Medical experts think that HDL tends to carry cholesterol away from the arteries and back to the liver, where it is passed from the body. Some experts believe that excess cholesterol is removed from atherosclerotic plaque by HDL, thus slowing the build-up. However, low HDL cholesterol levels (lower than 35 mg/dL) may result in a greater risk for heart disease.

 

This picture illustrates the build up of plaque that can occur in our arteries when cholesterol is not controlled: