Cholesterol

Without cholesterol, your body couldn't function. This soft, waxy-textured substance is crucial in building cell membranes; it's a key ingredient in the biochemical synthesis of Vitamin D; it helps the body manufacture bile, which helps break down dietary fat; and it's used to make estrogen, testosterone and progesterone along with a half-dozen other essential hormones.

Yet despite this remarkable list of benefits, most of us think of cholesterol as a bad thing. That's not surprising, given that too much cholesterol can be fatal. If your total cholesterol count is above 200 mg/dL (or milligrams per decileter—a tenth of a liter) of blood plasma, you need to start worrying.

Cholesterol per se isn't the problem. Rather, it's that it can't travel the bloodstream alone, but must be ferried around the body in molecules called lipoproteins. One type, known as low-density lipoprotein, or ldl, is prone to attach to the walls of blood vessels, forming so-called plaques—tough, thick deposits that can stiffen and narrow the arteries, just as mineral deposits can narrow the pipes in a house.

If a blood clot or a chunk of loosened plaque gets trapped in one of these narrow spots, it can block the vessel completely. If it shuts off the blood supply to the heart, you have a heart attack; if it keeps blood from reaching the brain, the result is a stroke. And even if there's no shutoff, the narrowing can lead to chest pains, shortness of breath or, in the case of the brain, reduced mental function. If the ldl component of total cholesterol is above 160 mg/dL, you could be in trouble. A good target for most people is 100 mg/dL or less.

Fortunately, the body has its own repair system: another form of lipoprotein, known as hdl, or high-density lipoprotein. Where ldl tends to clog arteries, hdl clears them out, removing ldl deposits from arterial walls and carrying them off to the liver for disposal. But if you don't have an hdl level of at least 40 mg/dL, you don't have enough to do the job.

What can you do about either problem? The first step is to change your diet. Because the body makes its own cholesterol, any you consume in your diet is superfluous—and pretty much any animal-based food (especially egg yolk) contains it. Beyond that, the saturated fats found in red meat, butter and whole milk are transformed into cholesterol inside the body, so limiting those is a very good idea.

Artificially thickened vegetable fats—so-called trans fats, or partially hydrogenated oils, found in stick margarine and many commercial peanut butters and baked goods, are just as bad as saturated fats. Olive oil and oils found in fish, by contrast, can help raise hdl in some people.

Exercise can often be useful in raising blood levels of hdl and lowering ldl as well. And if neither diet nor exercise are sufficient, statin drugs (Lipitor, Crestor and Pravachol are just a few examples) or niacin (vitamin B3) can lower ldl significantly.

—Michael D. Lemonick