Understanding cholesterol is more than figuring out what's good and bad.

Although much is known about this waxy substance that's in all body cells and its relationship with heart disease, much is still uncertain. Doctors suspect that the relationship may be more complicated than previously believed.

The September issue of Mayo Clinic Women's HealthSource provides an overview of cholesterol and recent news about cholesterol medications.

The general consensus has been that lowering low-density lipoprotein (LDL) or "bad" cholesterol helps reduce the risk of plaque accumulation on blood vessel walls. This accumulation, called atherosclerosis, can lead to heart attack or stroke.

Regular exercise and a healthy diet are known to reduce LDL levels and increase high-density lipoprotein (HDL), the "good" cholesterol that removes excess cholesterol from the body. When diet and exercise aren't enough to control cholesterol levels, medications can help lower LDL levels. Statins are some of the most popular and effective drugs for this task. They prevent the formation of cholesterol in the liver and reduce the risk of dying from cardiovascular disease.

Earlier this year, statins were involved in a study called ENHANCE. Researchers compared the drug ezetimibe-simvastatin (Vytorin), which combines a statin with a cholesterol-absorption inhibitor, with the stand-alone statin simvastatin (Zocor). Researchers hoped that the combination drug would lower LDL cholesterol even more than the statin alone. However, they found the combination drug didn't reduce thickness of plaque in the blood vessel walls any more than the statin did.

The study garnered considerable attention because it seemed to question the long-held belief that lowering LDL cholesterol is an effective way of preventing heart attack and stroke. But many doctors have misgivings about that interpretation, the accuracy of the results and how the findings have been generalized.

Because of the many environmental and genetic factors involved in heart disease, some drugs may be more effective than others in preventing atherosclerosis. There's no evidence that ezetimibe is unsafe and, in fact, taking this drug may allow for a lower statin dose and reduce the statin side effects such as muscle pain. Results from additional studies on ezetimibe are expected in a few years.

When diet and exercise aren't enough, evidence still supports that any therapy that lowers LDL cholesterol appears to provide benefits, and there are many options. Consult a doctor about the best ways to manage cholesterol.

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