What Exactly Is Cholesterol?

Although cholesterol has gotten a bad rap over the years, it’s not, by itself, a bad thing.

Cholesterol is a soft, faintly yellow, naturally occurring waxy substance found in cell walls and membranes throughout your body, including your brain, nerves, muscles, skin, liver, intestines, and heart. It’s one of several fats, or lipids, your body produces. Without enough cholesterol, you simply couldn’t live.

What Is Cholesterol?

You use cholesterol to produce sex hormones (including estrogen, progesterone, and testosterone), vitamin D, and bile acids that help you digest fat. However, you need only a relatively small amount to take care of all of these things. And your body (your liver, intestines, and even skin) manufactures plenty of it — about three or four times more cholesterol than most Americans eat. That means you could go the rest of your life without ever consuming another bite of cholesterol and you’d be just fine. (Although there’s no need to do so. In actuality, eating too many foods that contain cholesterol is not the main cause of high blood cholesterol.)

Like so many things, cholesterol isn’t bad for you unless there’s too much of it, at which point it begins to cause trouble. The story isn’t quite that simple, however. As you probably already know, there are different kinds of cholesterol — some bad, some good. And how much you have of each type makes a tremendous difference in your likelihood of developing coronary heart disease (CHD).

It’s actually not cholesterol per se that’s good or bad for you, but the “vehicle” through which it travels your bloodstream. Because cholesterol is waxy, it can’t mix with blood, which is watery. Like oil in a salad dressing, it remains separate. To enter the cells and tissues where it’s needed, then, it hooks up with proteins, creating special transporters called lipoproteins. Think of these as submarine-like bubbles that carry cholesterol around the body. Some of these “submarines” are friends, but most are foes.

Low-density lipoproteins, or LDLs, are the primary foes — the archenemies, in fact. LDLs carry most of the cholesterol (75 to 80 percent) in the blood, depositing it into the cells, including the arteries. There these particles contribute to the formation of plaque, which narrows the arteries. That reduces the amount of blood that can get through, diminishing the amount of oxygen that reaches the heart.

Some LDL types are more dangerous than others. Smaller, denser LDL particles are more damaging to blood vessels because it’s easier for them to cross the lining of the vessel and burrow into the vessel wall.

Most people won’t know what type of LDL they have because the tests to determine it are too expensive and complicated for the typical doctor’s office. If you already have coronary heart disease (CHD), or have a strong family history of CHD, and your doctor has sent you to a cardiac specialist, that doctor may run more detailed tests to better understand your risk. But it doesn’t matter much, as the focus remains the same regardless: Lower the amount of LDL in your body.

So what’s the ideal LDL level? That depends on your personal history and other risk factors for CHD. But if you’re a man 45 or older or a woman 55 or older and don’t have CHD, diabetes, hypertension, or a family history of premature CHD, and don’t smoke, here’s what you should aim for (levels are measured in milligrams per deciliter, or mg/dl — a deciliter is about 3 ounces). An optimal LDL level is less than 100 mg/dl. 130-159 mg/dl is borderline high and anything above 160 mg/dl is high.

Everything from your weight to whether or not you smoke to your family health history — even the amount of stress you’re under — affects your LDL level. Of course, your diet makes a difference, too, particularly the types of fats you eat.

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