Cholesterol 101

By S. Johanna Robledo Wade

What is cholesterol?
Cholesterol is a type of steroid that circulates in the blood (and it is also part of some fats). It plays a pivotal role in generating hormones, and it helps create cell membranes.      

Where does it come from?
We consume some of it through meat and dairy products. However, the liver manufactures about 85 percent of the cholesterol that circulates in the body, says Lora A. Sporny, R.D., associate adjunct professor of nutrition and education at Columbia University. The amount it churns out depends on a few factors, and genetics is a big one. “Some people have livers that willy-nilly make too much,” says Sporny. Another one is body size. In general, the smaller you are, the less cholesterol your body produces. (This is a big reason why living active and losing weight can improve your levels.) The third factor that affects cholesterol production has to do with diet. Certain foods, especially those high in saturated and/or trans fat, can trigger the liver to produce more—sometimes, a lot more. It works the other way, too, though. Fiber, for instance, can bind with cholesterol in the digestive tract and move it out of the body. Similarly, plant sterols help to block cholesterol from getting into the digestive system at all. So products containing at least 400mg of plant sterols per serving eaten twice per day for a daily total intake of at least 800mg, as part of a diet low in saturated fat and cholesterol, may be helpful to you in maintaining cholesterol levels within normal limits and reducing the risk of heart disease.

What’s the difference between “good” and “bad” cholesterol?
Cholesterol can’t dissolve in the blood, so it travels through the body by piggybacking onto certain proteins. High-density lipoproteins (HDL), aka “good cholesterol,” act like a clean-up crew, picking up the excess fat from the blood vessels and bringing it back to the liver for disposal. Low-density lipoproteins (LDL), aka “bad cholesterol,” deposit the waxy stuff onto blood vessels. When LDL becomes high, the risk of heart attack and stroke increases as well.

Why should we care about cholesterol levels?
If your cholesterol levels remain high over time, more and more of that fat begins to cake artery walls. Eventually, the buildup can stiffen the vessels and contribute to atherosclerosis, which raises the risk of heart attack and stroke.

Are there differences between the sexes when it comes to cholesterol?
Yes and no. Sex doesn’t determine how much cholesterol in general is in the body. Nevertheless, estrogen helps the body make more HDL, so premenopausal women tend to have more of the good cholesterol than men. After menopause, HDL levels tend to fall.

Men and women over the age of 20 should consider having their levels checked; if the results are within the healthy range, doctors usually recommend tests every five years until they are in their 40s or 50s, and more regularly thereafter.