Clinical Overview
Reviewed by Michael Fuller, MD
Cholesterol is a member of the lipid family. Lipids are fats and fat-like substances that appear in plants and animals. Cholesterol is an essential nutrient that the body acquires partially through diet, as well as through the liver’s manufacture of it. Despite its reputation, cholesterol is an essential lipid that repairs cell membranes, manufactures vitamin D, and creates hormones.

Several types of lipids exist. The three most prominent are: low density lipoproteins (LDL), high density lipoproteins (HDL), and triglycerides.

• LDL:
  
  LDL carries approximately 75 percent of the blood’s cholesterol to your body’s cells. In most cases, LDL is harmless. However, if it collects on arterial walls, plaque can form and cause damage. LDL may also lower your body’s level of nitric oxide, which normally allows blood to freely flow. When this happens, your arterial walls may constrict and reduce blood flow, resulting in a condition called atherosclerosis (hardening of the arteries). Artherosclerosis is often a precursor to coronary artery disease.
  
  

  Low levels of LDL are important to your health.

• HDL
  
  HDL rids the artery walls of cholesterol and returns it to the liver. Your HDL level should be high (above 45 mg/dl). This will help prevent narrowing of your arteries, and thus prevent heart attacks.

• Triglycerides
  
  High levels of triglycerides are often associated with obesity and diabetes. They are a combination of fat molecules and cholesterol that may harm the heart by partnering with LDL to form dense packets of more-dangerous LDL. Triglycerides may cause blood clot formation, leading to heart attack.
  

A total cholesterol reading of over 200 mg/dl is considered too high, and thus unhealthy. More than half of American adults have readings over 200, compared with only 7 percent of Asian adults. The American lifestyle of a high-fat, low-fiber diet is a risk factor for high cholesterol levels. Obesity and lack of exercise also contribute to high cholesterol levels.

In general, women have higher cholesterol levels than men, especially between the ages of 20 to 34 and after menopause. Women should pay special attention to their HDL levels. Studies show that women with total cholesterol over 200 and HDL below 50 had a higher death rate than women with HDL above 50.

Genetics have also been shown to play a role in cholesterol levels. People from families with a history of heart disease should closely monitor their cholesterol levels.

Unhealthy cholesterol levels may contribute to half of the deaths due to coronary artery disease in the United States. High cholesterol also doubles your risk for a heart attack. Faced with these statistics, many people are working hard to improve their heart health.

To evaluate your cholesterol, your doctor will measure your HDL and total cholesterol levels. LDL is difficult to measure on its own, but your doctor will be able to calculate it.

Several medical groups suggest that you should get your cholesterol measured periodically starting at age 20. In the 12 hours before your reading, you should not exercise, and not eat or drink anything other than water.

If you register a normal cholesterol level, you may not need to be re-tested for 5 years, unless you undergo a lifestyle change during that time. People with high cholesterol should be monitored every two to six months.

Most people who should be tested are not. Residents of the northeastern United States, older people, whites, and those with private health insurance are more likely to monitor their cholesterol levels.

Last updated: Feb-11-08