Harvard Men's Health Watch

Lowering cholesterol: Is there a limit?

Strict vegetarians don't get any cholesterol in their diets, but they still have plenty of cholesterol in their blood. So does everyone else. In fact, even folks in the burger and fries crowd can trace about two-thirds of their blood cholesterol to their metabolism, not their appetites.

Cholesterol is manufactured in the liver. Diet certainly influences how much your liver produces — when you eat more saturated or trans fat, your liver churns out more cholesterol — but even with a vegetarian diet, regular exercise, and a trim build, the liver produces an irreducible minimum amount of cholesterol. It's a good thing, too, since cholesterol makes vital contributions to health. For one thing, it is a major component of all human cell membranes. For another, it is the building block of steroid hormones, including cortisol, estrogen, and testosterone.

Scientists know that cholesterol is essential, but they also know that high levels of LDL ("bad") cholesterol dramatically increase the risk for heart attacks, angina, peripheral artery disease, and stroke. And they have also discovered that reducing LDL cholesterol reduces risk. As studies have accumulated, the targets for LDL cholesterol levels have steadily declined. For healthy people, an LDL of 160 milligrams per deciliter (mg/dL) was once considered acceptable; now 130 mg/dL is okay, 100 mg/dL, ideal. For people with stable coronary artery disease, diabetes, hypertension, or other major cardiovascular risk factors, the targets are more stringent still: 100 mg/dL is okay, 70 mg/dL or less, ideal. And for patients with unstable coronary heart disease, it's 70 mg/dL or bust.

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