What is cholesterol, and why does it matter?
If you have high cholesterol, or your numbers have been trending upward, it’s wise to take it seriously. High cholesterol—what doctors call hypercholesterolemia— is a major driver of cardiovascular disease and a leading cause of death and disability. Elevated levels of low-density lipoprotein (LDL) are particularly dangerous and the primary focus of attention. Left unchecked, high cholesterol can lead to a heart attack, stroke, or the need for a stent or bypass surgery.
Cholesterol comes from two sources: the dietary cholesterol you consume in food, and the cholesterol your liver makes and releases into your bloodstream. Though many people fret about the cholesterol in their diets, only 20% to 25% of the cholesterol in your blood actually comes directly from what you eat. Your body makes the other 75% to 80% from raw materials such as fats, sugars, and proteins.
Cholesterol is a fat-like substance (lipid), and everyone requires a certain amount to function properly. It’s a key component of cell membranes and other structures; in fact, you can think of it as a kind of building block for body tissues. Certain glands use cholesterol to produce corticosteroids and other hormones, including testosterone, estrogen, and vitamin D. Cholesterol is also used to make bile acids, released by the gallbladder, that help you digest and absorb nutrients. It’s so important that the brain actually makes its own cholesterol, rather than relying on absorbing it from elsewhere in the body.
The problem isn’t having cholesterol in your bloodstream—it’s having too much, especially of the wrong kind. When that happens, cholesterol can irritate the arteries, accumulate within them, and damage blood vessel walls, setting off reactions that cause trouble. While this process, known as atherosclerosis, starts early in life, the resulting problems typically don’t appear until years later, after damage has accrued over the course of several decades.