Low-density lipoprotein (LDL) is the major carrier of cholesterol in the blood. LDL cholesterol is commonly known as "bad cholesterol". Too much LDL will build up with other substances along the artery walls that feed the heart and brain. They combine to form plaque (atheramatous plaques), hard, thick deposits that clog the arteries. This leads to a condition called atherosclerosis.
This condition can become quite dangerous. For example, if a clot ( thrombus) forms close to the plaque, it will block blood flow to parts of the heart muscle, causing an myocardial infarction, or a heart attack. Basically, an infarction means that the tissues the blood flow nourished and supported are now dead. Heart attacks are the number one killer of men and women world-wide.
Now, if a clot blocks blood flow to the brain, this will cause a stroke. A stroke is the 3rd leading cause of death in the United States alone. If one survives a stroke, he or she will struggle with a variety of difficulties including paralysis, vision difficulties memory loss and speech/language problems, most of which are irreversible.
Levels of LDL cholesterol must remain below 160 mg/dL unless you already have heart disease. Then, your LDL choelsterol levels should be less than 100 mg/dL. Lower levels of LDL cholesterol are good as they lower your risk of heart disease, heart attack, and stroke.
As a general rule of thumb, LDL cholesterol levels of less than 100 mg/dL are considered optimal (best), while 100-129 mg/dL are considered near optimal. 130-159 mg/dL is considered borderline high, while 160-189 mg/dL is considered high, and levels of 190 mg/dL and above is very high levels of LDL choelsterol.